Utilization of Natural Kapok and Coconut Fiber in Thermally Insulated Sustainable Concrete Design

Utilization of Natural Kapok and Coconut Fiber in Thermally Insulated Sustainable Concrete Design | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Utilization of Natural Kapok and Coconut Fiber in Thermally Insulated Sustainable Concrete Design Gulsah Susurluk, Hakan Sarıkaya, Levent Bostanci This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4099400/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 18 Oct, 2024 Read the published version in Environmental Science and Pollution Research → Version 1 posted 6 You are reading this latest preprint version Abstract Nowadays, when regenerable alternative green sources are attracting more caution under sustainability targets, kapok and coconut fibers, known as natural fibers, have come to the fore as a very significant raw material source. In this experimental study, compressive strength, thermal insulation and pore structure characteristics of kapok fiber (KP) and coconut fiber (CC)-incorporated concrete samples under different curing conditions were analyzed. For that purpose, randomly distributed fiber-incorporated concrete mixtures containing 0%, 0.5%, 1% and 1.5% KP and CC fiber by the weight of cement were prepared and under H 2 O 2 and NaClO curing conditions, the effects of KP and CC fiber inclusion on properties mentioned above of fiber-incorporated concrete samples were researched in detail. Experimental results depict that a maximum thermal conductivity coefficient decrease of 24.31% was detected at a content ratio of 1.5% by the reason of the pore modification effect of used natural fibers in the H 2 O 2 curing group. Because of the remarkable pore modification effect of KP fiber incorporation into the cement matrix compared to the CC fiber inclusion cases, strong linear correlations revealing the insulation-strength mechanism could be detected for both H 2 O 2 and NaClO curing cases. This work intends to promote sustainable development in the building industry by integrating natural fibers into concrete mixtures as an innovative design approach. Kapok fiber Coconut fiber Pore structure Thermal insulation Compressive Strength Sustainability Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 1. Introduction Conventional concrete manufacture substantially makes a significant to CO 2 emissions because of the high energy needed to generate Portland cement, the main binder of concrete (Kahan et al. 2023; Althoey et al. 2023 ). Recent searches have stated that roughly 0.9 tonnes of CO 2 are released while manufacturing 1 ton of Portland cement, which accounts for approximately 5% of the human-induced CO 2 emissions globally (Althoey et al. 2023 ; Nassar et al. 2022 ). Therefore, in recent years, a vast majority of researchers have searched for sustainable resources for environmentally friendly cement and concrete, to decrease CO 2 emissions. Due to a substantial surge in the demand for sustainable concrete, which is one of the most extensively utilized construction materials globally (Althoey et al. 2023 ). Concrete is a material that is fragile and has a low ability to withstand tension and strain. When randomly dispersed natural fibers with high technical specifications are utilized to reinforce the matrix (mortar and concrete), a graded increment in tensile strength and tensile strain capacity is determined (Avubothu et al. 2022 ; Riza et al. 2020 ; Sarikaya and Susurluk 2019 ). Fibers interchange the action of the matrix (mortar and concrete) when cracks form and the ability of fiber-containing concrete to prevent cracks, especially microcracks, is widely known (Avubothu et al. 2022 ; Riza et al. 2020 ). These weaknesses of concrete can be improved by incorporating fibers, especially natural renewable fibers which are recently gaining attention with the aim of sustainable design in the construction industry (Riza et al. 2020 ). Hence, renewable fibers such as kapok and coconut from natural fibers have increasingly been investigated in the fiber-incorporated sustainable concrete design (Damfeu et al. 2016 ). Kapok fiber is a type of natural fiber made up of single-celled fibers, similar to cotton fiber. Nevertheless, it possesses a density of 0.29 g/ cm 3 , which is seven times lower than that of cotton fiber (Damfeu et al. 2016 ). Kapok fiber has the highest void ratio of any fiber type, around 90% (Sun et al. 2023; Yang et al. 2018 ). Nevertheless, it has a buoyancy that may be twenty times its weight (Damfeu et al. 2016 ) and displays better thermal properties and performance compared to the most used other kinds of natural fibers in concrete mixtures (Gobalakrishnan and Saravanan 2019 ). This gives the kapok fiber outstanding characteristics of thermal insulation, sound insulation, and extraordinary buoyancy (Sun et al. 2023; Cao et al. 2010 ). Conventionally, kapok fibers were commonly used for filling water safety equipment, stuffing bedding and upholstery, and providing fabric insulation (Zheng et al. 2021 ; Yeo et al. 2022 ; Liu et al. 2016 ). They also have extensive potential applications as materials for oil absorption and soundproofing (Sun et al. 2023; Liu et al. 2016 ). Nevertheless, there is a scarcity of information regarding its application in concrete mixtures, and its performance in terms of serviceability remains unexplored. Coconut fiber has also low density and mass such as the kapok fiber mentioned above. However, since coconut fiber causes less pollution during the formation phase, health hazards are minimized and it is also environmentally friendly (Nawab et al. 2023 ). In comparison to the utilization of Kapok fiber in sustainable concrete design, coconut fibers are widely utilized as reinforcing material in construction technology (Damfeu et al. 2016 ). For the first time, a cement composite containing coconut fiber was produced in Thailand and used as a roof covering to both decrease heat transfer mechanisms and enhance energy savings (Gupta and Kumar 2019 ). Mintorogo et al. (2015) utilized coconut fibers in this study to increase thermal insulation and reduce energy consumption in concrete slab roof coverings. As a result of the study, it was reported that the savings achieved in roof surface thermal insulation with coconut fibers differed by 13°C compared to traditional reinforced concrete containing zero fiber contribution slab roofing and the reduction in energy consumption was approximately 3% (average) and 9% (maximum). Edgar et al. ( 2021 ) evaluated the effective use of mortars modified with coconut fibers as facade cladding layers to increase thermal comfort in building structures. Thermal properties of coconut fiber-incorporated mortars were also investigated by monitoring temperature and humidity changes as the study continued. Results show that there is an effective to enhance the thermal insulation in building structures with coconut fiber-incorporated mortars. Avubothu et al. ( 2022 ) investigated the durability properties of coconut fiber-incorporated concrete under high-temperature conditions. Based on the reported results, major enhancements were determined on the properties of coconut-incorporated concrete compared to conventional concrete under high-temperature conditions. Ali et al. ( 2012 ) reported that the mechanical features of coconut fiber-incorporated concrete varied depending on the content and length of fibers in mixtures. In their experimental study, coconut fibers with lengths of 25, 50 and 75 mm were incorporated into the mixtures at contents of 1%, 2%, 3% and 5%, by weight of cement. According to the experimental study, it was reported that coconut-incorporated concrete with a fiber length of 50 mm and a fiber content of 5% shows superior mechanical features compared to fiber-free cases. Bijo and Unnikrishnan ( 2022 ) investigated the mechanical properties and impact resistance of coconut and polypropylene fiber-incorporated concrete. From the experimental study, it was observed that the maximum improvement in impact strength of coconut fiber-incorporated concrete was 94% when the fiber length was 50 mm and 134% when the fiber length of polypropylene fiber-incorporated concrete was 12 mm. Varghese and Unnikrishnan ( 2023 ) examined the impression of coconut fiber addition on the mechanical features of concrete samples. Fibers with lengths of 25, 50 and 75 mm were incorporated into the mixtures at contents up to 2%, by weight of cement. According to the experimental results, it was detected that coconut fiber incorporation deeply enhanced the mechanical properties of samples, especially up to 30% improvement in shear strength properties was determined for both fiber inclusion cases of 50 mm and 75 mm. Nawab et al. ( 2023 ) studied a study on improving the effect of coconut fiber-incorporated mortars containing silica fume and metakaolin. The findings of this study demonstrate the beneficial effects of adding coconut fiber to calcium-silicate-based mixtures. This addition improves the thermal insulation and mechanical properties of samples that contain industrial by-products. The results also offer valuable information for creating environmentally friendly and high-performing cement-based materials. Today, sustainability regulations in the construction industry aim to promote sustainability by encouraging the use of industrial by-products and natural resources in the design of cement-based materials, and most previous research has focused on these topics (Mwaikambo and Bisanda 1999 ; Xu et al. 2017 ). Moreover, in recent years, with the introduction of the concept of sustainability into industrial life and the transfer of this awareness to consumers, the search for contributing to a sustainable future has begun in the construction industry, as in all industrial areas. Kapok and especially coconut fibers have also become widely investigated sustainable materials in recent years due to their renewable, biodegradable and reusable features. Nowadays, when regenerable alternative green sources are attracting more caution under sustainability targets, kapok and coconut fibers are pointed out as substantial resources of raw materials due to their great potential in sustainable cement-based material design. The increasing number of recently conducted studies analyzing the inclusion of coconut fibers into cement-based materials to enhance their mechanical and thermal insulation properties, as well as the results obtained from this study, is worthy of attention due to the implemented comparative H 2 O 2 and NaClO curing conditions. Moreover, the motivation for this manuscript is based on the utilization of kapok fiber in cement-based mixtures as a unique kind of natural fiber used for the first time, indicating a great potential for the design of eco-friendly cement-based material as a valuable sustainable resource. 2. Materials and methods 2.1. Materials This study aimed to achieve a sustainable target by incorporating kapok and coco fibers into concrete mixtures manufactured according to the TS EN 206 + A2 standard (2021). Afyon Cement provides Ordinary Portland Cement (OPC) of 42.5 R type, which adheres to the TS EN 196-1 standard and is utilized in concrete compositions (2019). The concrete mixtures were made using tap water sourced from the city waterworks and aggregates supplied by Oktaş Concrete. The chemical compositions and physical properties of used cement and aggregate are presented in Table 1 . The physical and mechanical properties of kapok and coconut fibers incorporated into the concrete mixtures are also shown in Table 2 . Table 1 Chemical compositions and physical properties of used cement and aggregate. Cement Aggregate Chemical composition (wt/wt %) SiO 2 Al 2 O 3 Fe 2 O 3 CaO MgO SO 3 Na 2 O K 2 O Cl - Loss on ignition Physical properties Density (g/cm 3 ) Specific surface area (cm 2 /g) 19.1 5.19 2.65 63.4 1.83 2.95 0.22 0.94 0.01 3.06 1.05 20.9 0.4 0.2 42.6 0.4 - <0.1 0.1 - - 2.41 Table 2 The physical and mechanical properties of kapok and coconut fibers Kapok fiber Coconut fiber Physical properties Density (gr/cm 3 ) 0.29 1.2 Moisture (%) 14 10 Length (mm) 8–35 20–150 Diameter (µm) 20–43 100–450 Mechanical properties Tensile strength (N/mm 2 ) 189 105–175 Initial modules (GPa) 4–11 4.6 2.2. Mix proportions In order to investigate the impact of adding kapok fiber (KP) and coconut fiber (CC) on the mechanical properties, thermal conductivity, pore structure, and microstructure morphology of concrete samples, we prepared seven different concrete mixtures. For this purpose, KP and CC were utilized in the concrete mixtures at contents of 0.5%, 1% and 1.5%, by weight of cement. In all mixtures the total amount of cement was kept constant. Table 3 tabulates the mix ratios of the concrete samples produced. There was a total of seven mixtures, which were labeled as S-0, KP-0.5, KP-1, KP-1.5, CC-0.5, CC-1, and CC-1.5. The samples were labeled with representing the S-0 without kapok fiber or coconut fiber, KP with kapok fiber and CC with coconut fiber content. The latter labels “0”, “0.5”, “1”, and “1.5” indicate the amount of fiber added to the concrete mixture in percentage. Table 3 Concrete mixture proportions used in the study Mix Cement (kg/m 3 ) Fine aggregate (kg/m 3 ) Coarse aggregate (kg/m 3 ) Kapok fiber (gr) Coconut fiber (gr) Water (kg/m 3 ) S-0 300 722 1111 - - 160 KP-0.5 300 722 1111 15 - 160 KP-1 300 722 1111 30 - 160 KP-1.5 300 722 1111 45 - 160 CC-0.5 CC-1 CC-1.5 300 300 300 722 722 722 1111 1111 1111 - - - 15 30 45 160 160 160 2.3. Sample preparation, curing conditions and testing procedures The concrete mixes were blended using a mechanical mixer in the experimental experiments and then poured into cube molds measuring 100 mm x 100 mm x 100 mm. During the preparation of the mixtures, mixing was carried out with the help of a vertical-axis mixer. Water was incrementally introduced into the mixtures until a uniform matrix was obtained. Tap water was used as the mixing water. When the concrete reached a specific consistency, fibers were added. Then, the concrete mixtures were poured into the usual cube molds and subjected to vibration to improve the consistency of the samples. A total of ten concrete samples were manufactured from each concrete mixture in order to conduct tests on strength, pore structure, thermal conductivity coefficient, and microstructure morphology. The concrete samples were stored in the mold at a temperature of 21 ± 1°C for the first 24-hour period. The samples were extracted from the mold the following day and underwent three distinct curing cases, including conventional water, H 2 O 2 and NaClO curing regimes, for a duration of 28 days till the testing period. A set of samples was immersed in water at room temperature of 21 ± 1°C. In the second curing group, a 5% H 2 O 2 solution in water was prepared. The specimens in the second group were then submerged in this solution. Similarly, a 5% NaClO solution in water was prepared for the remaining curing process. In both curing regimes of H 2 O 2 and NaClO, the curing process was performed in the form of water curing method. The cured samples were subjected to tests to assess their compressive strength and thermal conductivity coefficient. Compressive strength, pore structure, thermal conductivity coefficient and microstructure morphology tests were subjected on the samples under curing conditions containing H 2 O 2 and NaClO, respectively. Figure 1 presents the implemented test program. Concrete samples measuring 100 x 100 x 100 mm underwent compressive strength tests. The compressive strengths were established by calculating the mean of three separate test results in accordance with the TS EN 12390-4 standard (2002). The remaining mixture samples that were not tested for strength were utilized to calculate the thermal conductivity coefficients and conduct mercury intrusion porosimetry (MIP) experiments on fiber-containing concrete mixtures. The thermal conductivity coefficient of the samples was measured using the ASTM C 1113-09 hot wire standard (2009). The thermal conductivity coefficient of each sample was tested five times for various locations using a QTM-500 device. The resulting values were averaged to obtain the final measurement. The mercury intrusion porosimetry test was utilized to determine the pore structure characteristics of the concrete samples, including total porosity, pore diameter sizes, and specific pore contents. The MPI test was assessed utilizing a QTM-500 device. The device is capable of detecting pore widths ranging from 3 to 360 micrometers. The microstructure morphology of the remaining specimens from the 28-day compressive strength test was determined using SEM (Scanning Electron Microscope) analysis. The powder form of sample pieces, which were precisely taken from the fracture surface of the compressive strength test, were coated with carbon and made suitable for microstructure analysis. SEM analyses were performed with the LEO 1430 VP model SEM device. 3. Results and discussions 3.1. Compressive strength test results Figure 2 illustrates the 28-day strength test for concrete samples containing KP fiber under three different curing conditions. The water group control sample achieved a strength of 49.76 MPa after a curing period of 28 days. The addition of KP to the concrete mixtures at content ratios of 0.5%, 1%, and 1.5% resulted in decreases in compressive strength of 6.45%, 9.12%, and 9.54%, respectively. The control sample of the H 2 O 2 group reached a strength of 47.25 MPa at 28 days of age. KP incorporation at 0.5%, 1% and 1.5% content ratios led to decreases in compressive strength by 10%, 12.84% and 12.99%, respectively. The NaClO group control sample reached a compressive strength of 45.18 MPa after a curing period of 28 days. For the fiber additions of the 0.5%, 1% and 1.5% fiber addition, the compressive strength decreases, which are 10.9%, 11.5%, and 11.73%, respectively. As seen in all curing groups, the strength of concrete at 28 curing age showed a trend that the higher the KP incorporation ratio, the lower the compressive strength. All mixture samples exhibited the highest compressive strengths when subjected to water-curing conditions with identical KP contents. Conversely, the samples exposed to NAClO curing conditions displayed the lowest compressive strengths. Incorporation of KP into the concrete mixtures even at a minimum content leads to a less strong matrix and diminishes the bonding mechanism between the interfacial transition zone (ITZs) of the fiber and cement matrix. As seen at higher KP contents even the reduction in strength tendency was observed, the decreases were limited such as 3.30%, 3.29%, 0.91% levels for water, H 2 O 2 and NaClO curing groups, respectively. Figure 3 displays the results of a 28-day strength test of CC-incorporated concrete samples under three different curing conditions. At 28 days old, the control sample with no fiber content obtained a compressive strength of 49.76 MPa. CC incorporation into the concrete mixtures at 0.5%, 1% and 1.5% content ratios led to reductions in strength by 5.52%, 6.43% and 8.46%, respectively. The compressive strength of the control sample in the H 2 O 2 group was determined to be 47.25 MPa after 28 days. In the case of the 0.5%, 1% and 1.5% content, the compressive strength decreases, which were 8.97%, 9.98%, and 10.6% respectively. The control sample from the NaClO group had a strength of 45.18 MPa after 28 days. On the other hand, in the 0.5%, 1% and 1.5% content mixtures, the reductions in compressive strength values were 9.22%, 10.33% and 10.97%, respectively. As seen in all curing groups, the compressive strength of concrete at 28 days of curing showed a consistent trend: the greater the CC incorporation ratio, the lower the compressive strength. This finding emphasizes the crucial impact of the ratio of CC fiber content on the compressive strength of concrete (Nawab et al. 2023 ; Ali et al. 2012 ), underlining the need of adjusting the fiber content to reduce strength reduction. Similar to the KP-incorporated fiber samples, the samples incorporated with CC also showed that the highest compressive strengths were achieved in samples cured with water, whereas the lowest strengths were observed in samples subjected to NAClO curing conditions, regardless of the CC content. Incorporation of CC into the concrete mixtures even at a minimum content leads to a less strong matrix and reduces the bonding mechanism between the ITZs of the fiber and cement matrix. As seen at higher CC contents even though the reductions in strength were observed, the decreases were limited such as 3.1%, 1.79%, and 1.92% levels for water, H 2 O 2 and NaClO curing groups, respectively. KPs and CCs with a lower density results in the formation of additional voids in the matrix. When cement modification was performed via KP and CC fiber at a content of 0.5%, there may not be a dominant modification in the fiber cement ITZs due to the fiber content increasing from 0.5–1% and 1.5%. This is shown with compressive strength results derived from all curing groups, indicating that the %0.5 fiber addition is critical (Varghese and Unnikrishnan 2023 ; Haigh et al. 2021 ). These phenomena may indicate a great potential for superior KP and CC-incorporated concrete properties for higher KP and CC incorporation cases such as an enhanced insulation target under a limited strength reduction. 3.2. Thermal conductivity test results Figure 4 illustrates the influence including KP on the thermal insulation efficiency of KK-incorporated concrete samples at 28-days for the three different curing conditions. The thermal conductivity coefficients of the KP-incorporated concrete mixtures ranged from 2.18 to 2.96 W/mK. As presented in Fig. 4 , the water control group sample had a thermal conductivity value of 2.96 W/mK after 28 days of curing. The thermal conductivity coefficient decreased by 13.85%, 17.22%, and 21.28% for KP contents of 0.5%, 1%, and 1.5%, respectively. The thermal conductivity coefficient of the control sample in the H 2 O 2 group was measured to be 2.92 W/mK. In the case of 0.5%, 1% and 1.5% KP containing, the decreases were 16.09%, 17.8% and 22.26% in mixtures, respectively. The NaClO group control sample achieved a thermal conductivity coefficient of 2.76 W/mK. On the other hand, in the 0.5%, 1% and 1.5% fiber-containing mixtures, the reductions in thermal conductivity coefficient values were 14.49%, 16.3% and 21.01%, respectively. When considering all curing groups, it was observed that the thermal conductivity coefficient of concrete decreased as the KP incorporation ratio increased at 28 curing age. The addition of KP into the concrete mixtures even at a minimum content led to causes lower conductivity values. Thus, the addition of KP into the concrete mixtures even at a minimum content leads to a less strong matrix and reduces the bonding mechanism between the ITZs of the fiber and cement matrix. Accordingly, at higher KP contents even though the reduction in the thermal conductivity tendency was observed, the declines were limited such as 8.62%, 7.34%, 7.62% levels for water, H 2 O 2 and NaClO curing groups, respectively. The thermal conductivity coefficients of the CC-incorporated concrete samples evaluated under different curing conditions at 28 days are indicated in Fig. 5 . According to Fig. 5 , the control sample with no fiber content had a thermal conductivity value of 2.96 W/mK at 28 days of age. Thermal conductivity coefficient decreases were found as 11.82%, 18.24% and 23.98% for 0.5%, 1% and 1.5% CC contents, respectively. Incorporating CC into the mixtures resulted in decreased conductivity levels. The thermal conductivity coefficient of H 2 O 2 group control sample was 2.92 W/mK. In the case of 0.5%, 1% and 1.5% CC containing, the decreases were 13.69%, 17.8% and %24.31 in mixtures, respectively. The thermal conductivity coefficient of the control sample from the NaClO group was measured to be 2.76 W/mK. On the other hand, at the 0.5%, 1% and 1.5% fiber content ratios, the decreases in thermal conductivity coefficient values were 10.5%, 17.02% and 23.55%, respectively. As far as all curing groups are concerned, the thermal conductivity coefficient of concrete at 28 curing age showed a trend that the higher the CC incorporation ratio, the lower the thermal conductivity coefficient. The addition of CC into the concrete mixtures even at a minimum content led to causes lower conductivity values. Hence, the addition of CC into the concrete mixtures even at a minimum content leads to a less strong matrix and reduces the bonding mechanism between the ITZs of the fiber and cement matrix. Thus, at higher CC contents even the reduction in thermal conductivity tendency was detected, the declines were limited such as 13.79%, 12.31%, 14.57% levels for water, H 2 O 2 and NaClO curing groups, respectively. 3.3. Mercury intrusion porosimetry (MIP) test results The primary characteristics of the pore structure significantly affect the mechanical and thermal insulation capabilities of concrete. Therefore, knowledge of the main pore structure properties such as total porosity (TP), total pore area (TPA), median pore diameter-volume (MPDv), median pore diameter-area (MPDa) are valuable to evaluate the performance of concrete (Bostanci 2020a ). Previous studies reported that fibers added into concrete mixtures improved (contribute positively to the pore structure) pore structure features of concrete samples under optimum conditions (Wang et al. 2023 ). The MIP was used to measure the main pore structure characteristics of 28-day concrete samples that contained KP and CC fiber. The pore structure parameters of concrete samples incorporating KP and CC fiber are listed in Table 4 . Table 4 MIP test results of KP and CC-incorporated concrete samples Mixture H 2 O 2 curing group NaClO curing group TP (%) TPA (m 2 /g) MPDa (nm) APD (4V/A) (nm) TP (%) TPA (m 2 /g) MDPa (nm) APD (4V/A) (nm) S-0 8.91 3.19 25.6 48.8 8.59 2.11 42.7 71.8 KP-0.5 11.67 6.64 17.6 31.9 12.47 9.31 5.6 24.4 KP-1 8.54 6.07 8.1 24 11.77 12.24 4.5 17.5 KP-1.5 9.77 6.44 5.7 26.2 14.89 15.04 4.9 18.9 CC-0.5 25.86 2.41 43.4 245.4 9.54 8.51 6.3 19.4 CC-1 11.24 5.71 14.2 35.4 22.39 7.63 5 59.9 CC-1.5 7.71 1.25 42.5 104.5 9.49 8.04 6.3 20.2 According to MIP results for samples cured in H 2 O 2 , the addition of KP into the mixtures approximately doubled the total pore area at all KP content ratios in comparison to control case. When fibers are incorporated into the cement matrix, it is expected that voids will form around the areas where the fibers are positioned in the matrix due to poor adhesion (Ng et al. 2015 ). On the other hand, the MPDa values showed a continuous decrease in direct proportion to the KP fiber content ratio. In comparison to the control sample containing zero fiber (S-0), the median pore diameter-area values of KP-incorporated concrete mixtures decreased by 31.25%, 68.35% and 77.73% respectively. Therefore, it can be said because the formation of a larger number of voids with smaller surface area diameters by fiber addition. A comparable trend was noted in the APD. In the incorporation of CC into the concrete mixtures cured in H 2 O 2 , similar results were observed at 0.5% and 1.5% content ratios in terms of pore properties, while a different trend was observed at 1% content ratio. In the NaClO curing condition, the total porosity was detected as 8.59% in the sample containing zero fiber (S-0), when both KP and CC fibers were added to the mixtures, TP values were enhanced in all mixtures. In the case of KP-containing mixtures, the TPA deeply increased in a range of 3.4–6.1 times. In comparison to the S-0, the MPDa values of KP-incorporated concrete mixtures declined by 31.25%, 68.35% and 77.73% respectively. Thus, both the TPA increase and a decline in APD were observed. In the case of 0.5%, 1% and 1.5% CC addition, the TPA increased by approximately four times in the same curing condition. At 0.5% and 1.5% content ratios, similar results were observed in terms of pore properties. There was a decrease of 85.24% in the MPDa at 0.5% and 1.5% content ratios, and 88.29% decrease at %1 content ratio. Comparable trends were noted in the APD’s of samples including KP and CC fiber. To gain a more comprehensive understanding of the effect of different amounts of fiber under different curing conditions on pore properties, the pore properties were discussed in detail. Figure 6 depicts the effect of the H 2 O 2 curing condition on pore properties at 28 days. The QTM-500 device was used to evaluate the pores ranging in size from 3 to 360,000 nm, as mentioned earlier. As seen in Fig. 6 .a, cumulative pore volume curves of all samples for all fiber addition cases indicate remarkable variations of the curves within the pore size ranges of 3–10 nm, 10–100 nm, and 100–360,000 nm. Within the size range of 3–10 nm, mercury exhibited a consistent and gradual drop initially. Subsequently, there is a rapid reduction in size within the range of 10–100 nm, followed by a consistent decline in the size range of 100–360,000 nm. As depicted in Fig. 6 .a, the CC-0.5 sample containing a 0.5% content ratio exhibited the highest pore volume throughout the range of pore diameters from 3 to 360,000 nm, where the measurement was carried out, following the determined maximum porosity and maximum APD values. Similarly, the KP-0.5 sample containing a 0.5% content ratio exhibited the second-highest pore volume behavior throughout the pore diameter range of 3-100 nm. Figure 6 .b reveals the content of pores in KP-incorporated concrete samples. As it is seen, while the smallest pore content (3–10 nm) formation determined in sample S-0 was 2.56%, higher pore contents in concrete samples KP-0.5, KP-1 and KP-1.5 (5.25%, 10.26% and 9.48%, respectively) were determined. This suggests that the addition of KP fiber has a notable impact on the creation of pores within the size range of 3–10 nm, and a similar trend was found within the range of 10–100 nm. On the other hand, in the size of 100–1000 nm, the highest pore formation was found as 22.83% in the control sample and lower pore proportions were found in all KP-incorporated samples for the above-mentioned pore content. It is evident that the presence of KP fiber significantly impacted the pore structure of the samples, particularly the gel pores and small capillary pores. Öz et al. indicated that an increase in fiber content leads to the creation of pores due to loose ITZs (Öz et al. 2023 ). Figure 6 .c reveals the content of pores in CC-incorporated concrete samples. As depicted in Fig. 6 .c, the incorporation of CC fiber into the mixtures led to a higher proportion of pores within the size range of 1000 − 360,000 nm. Furthermore, the addition of CC fiber caused a decrease in pore sizes within the range of 10–100 nm. At this point, it is clearly said that while both KP and CC fiber dominated the pore structure of samples, the mostly affected pore sizes were reversed. In contrast to KP fiber addition, CC fiber dominated mostly large capillary pores and macro pores formation. Figure 7 indicates the effect of NaClO curing condition on pore properties at 28 days. As shown in Fig. 7 .a, cumulative pore volume curves of all samples indicate remarkable variations of the curves within the pore size ranges of 3–10 nm, 10–100 nm, and 100–360,000 nm. Within the size range of 3-100 nm, there is a rapid decrease in the accumulation of mercury initially, followed by a regular decline in the size range of 100–360,000 nm. As depicted in Fig. 7 .a, the CC-1 sample containing 1% content ratio exhibited the highest pore volume throughout the range of pore diameters from 3 to 360,000 nm, where the measurement was carried out, following the determined maximum porosity and maximum APD values. Similarly, the KP-1.5 sample containing 1.5% content ratio exhibited the second-highest pore volume behavior throughout the pore diameter range of 3-100 nm. Figure 7 .b indicates the content of pores in KP-incorporated concrete samples. As it is shown, while the highest pore content (100–1000 nm) formation determined in sample S-0 was 18.87%, smaller pore contents in concrete samples KP-0.5, KP-1 and KP-1.5 (10.99%, 5.13% and 4.99%, respectively) were determined. A similar behavior is observed within the size range of 100,000-360,000 nm. Unlike, in the size of 3–10 nm, the smallest pore formation was achieved in the control sample and higher pore proportions were achieved in all KP-incorporated samples for the above-mentioned pore content. At this point, it can be said that the pore structure of samples was positively affected due to the addition of KP fiber, especially gel pores. This tendency towards the formation of pores due to a loose ITZs with enhancing fiber content was indicated by Öz et al. ( 2023 ). Figure 7 .c indicates the content of pores in CC-incorporated concrete samples. As it is shown, while the highest pore content (100–1000 nm) formation achieved in sample S-0 was 18.87%, smaller pore contents in concrete samples CC-0.5, CC-1 and CC-1.5 (5.29%, 4.82% and 7.07%, respectively) were achieved. On the other hand, the control sample exhibited the lowest pore formation, ranging from 3–10 nm, compared to the samples containing KP fiber under the NaClO curing condition. Moreover, the highest pore contents are minimum for a 1.5% content level in the same curing condition for both KP and CC fiber. As an obvious result, two different fibers exhibited similar behavior in the same curing condition. The estimated pore fractions indicate that the inclusion of both CC and KP fibers results in a reduction in pore size in the cement matrix, regardless of the kind of fiber used. This effect is shown when the cement is cured in the NaClO and is particularly noticeable in the decrease of medium-sized capillary pores. 3.4 Optimum fiber content, type and curing media in terms of compressive strength – pore structure - insulation relationships 3.4.1. Samples under H 2 O 2 curing condition Figure 8 depicts the impact of including KP and CC fibers on the pore structure, thermal conductivity and compressive strength characteristics of concrete samples when subjected to H 2 O 2 curing conditions. This examination aims to enhance the comprehension of the effects of KP and CC fiber inclusion on these properties. As previously stated, the addition of 0.5%, 1% and 1.5% KP led to reductions of 16.09%, 17.8%, and 22.26% in thermal conductivity values, compared to the control sample in the H 2 O 2 curing group. In Fig. 8 .a, the results clearly indicate that thermal conductivity values decrease at a maximum content ratio of 0.5%. The decline in thermal conductivity values is attributed to the modifying pore structure related to the fibers. Thus, this decrease in conductivity also resulted in a reduction in compressive strength values. KP incorporation at 0.5%, 1% and 1.5% content ratios resulted in reductions in compressive strength by 10%, 12.84% and 12.99%, respectively. Thus, when it involves fiber loading, the thermal conductivity values indicated a reduction, whereas the reductions in compressive strength values revealed a limited trend. As previously stated, the addition of KP fiber has an important effect on the formation of pores within the size range of 3–10 nm. This same trend was also observed within the range of 10–100 nm. On the other hand, in the size of 100–1000 nm, the highest pore formation was found as 22.83% in the control sample and lower pore proportions were found in all KP-incorporated samples for the above-mentioned pore content. At this point, the significant impact of KP fiber addition was dominant especially on gel pores and small capillary pores. As stated before, in the cases of 0.5%, 1% and 1.5% CC incorporation into mixtures, led to 13.69%, 17.8% and %24.31 decreases in thermal conductivity values and resulted in %8,97, %9,98 ve %10,6 decreases in the compressive strength values, respectively. In Fig. 8 .b, the results clearly report that thermal conductivity values decrease at a maximum content ratio of 0.5%. As seen in the KP fiber incorporation case, while the thermal conductivity values reduced, the reductions in compressive strength values showed a proper trend. In contrast to the KP fiber addition case, CC fiber dominated effectively on capillary and macro pore formation. Figure 9 presents the insulation-strength relationships of concrete samples under H 2 O 2 curing conditions, revealing an understanding of the impact of KP fiber addition on pore contents, thermal conductivity, and compressive strength characteristics. When the change in pore proportions, thermal conductivity and strength values by the inclusion of KP fiber into concrete mixtures were examined, the detected R 2 values seen above indicate strong linear correlations among the thermal conductivity, compressive strength and the pore contents. The experimental R 2 values determined by the correlations between pore development and thermal conductivity coefficient reveal an understanding of the improved insulation process, this tendency is also indicated in the study by Bostanci ( 2022 ). As shown in Fig. 9 .a and 9.b, good linear correlations between the specific pore proportions within the size range of 100–1000 nm and 3–10 nm. The thermal conductivity measurements obtained correlation coefficients of R 2 ranging from 0.92 to 0.74. Despite the average pore diameters being lower, the addition of KP fiber in the matrix caused the formation of gel pores and small capillary pores, which significantly contributed to the insulation purpose. Furthermore, a significant correlation was observed between the pore content within the range of 100–1000 nm and the 28-day compressive strength measurement, with an R 2 value of 0.97. Furthermore, an important correlation was observed between the amount of pores ranging 3–10 nm and the compressive strength, with an R 2 value of 0.82. The experimental results indicate that even a small amount of KP fiber added into the concrete significantly enhances its thermal insulation ability compared to the fiber-free case. The modified KP-incorporated pore structure was effective in optimizing the desired thermal insulation with predictable strength loss. However, when CC fibers were included, the modifications in pore characteristics of the modified structure were not sufficient to completely explain the mechanism for the insulating strength in the CC-incorporated samples. Therefore, advanced analysis is required to reveal the insulation-strength mechanism of samples containing CC fiber. 3.4.2. Samples under NaClO curing condition Figure 10 depicts the impact of including KP and CC fibers on the pore structure, thermal conductivity and strength characteristics of concrete samples. This investigation specifically focuses on the relationship between these variables under NaClO curing conditions. As previously mentioned, in the case of 0.5%, 1% and 1.5% KP addition, the decreases in thermal conductivity values were 14.49%, 16.3% and 21.01% in comparison to the free-fiber case in the NaClO curing group, respectively. The decrease in thermal conductivity values can be related to the modified pore structure, resulting in a limited decrease in compressive strength values. Particularly under the H 2 O 2 curing condition, the compressive strength values decreased by 10.91%, 11.5%, and 12.73%, respectively. Previous studies have indicated that the inclusion of both KP and CC fiber plays a major role in the creation of pores within the size range of 3–10 nm. On the other hand, in the size of 100–1000 nm, the highest pore formation was found as 18.87% in the control sample and lower pore proportions were found in all KP-incorporated samples for the above-mentioned pore content. At this point, the significant impact of KP fiber addition was especially on gel pores formation. As stated before, in the case of 0.5%, 1% and 1.5% CC incorporation into mixtures, 10.5%, 17.02% and %23.55 enhancements on thermal insulation properties were measured. As expected, respectively %9.22, %10.33 ve %10.97 reductions in the compressive strength values were also detected due to the modified pore structure of samples with lower conductivity values. Similar to the KP fiber inclusion case, the thermal conductivity values decreased, and the declines in compressive strength values exhibited a suitable trend. Moreover, as seen in Fig. 10 .a and 10.b, the macro pore formation within size range of 10000-360,000 nm was minimum at 1.5% fiber addition both for KP and CC fiber incorporation cases under the NaClO curing condition. In fact, the utilization of both KP and CC fibers played a similar role in the formation of similar pore fractions in the same curing condition. Figure 11 shows the significant correlations between the insulation-strength mechanism and the inclusion of KP fiber, specifically under the NaClO curing condition. This investigation aims to understand the impact of KP fiber on the mechanism. When the changes in the pore proportions, thermal conductivity coefficient and strength values by the inclusion of KP fiber into the cement matrix were examined, the obtained R 2 values reveal an effective linear correlation among the thermal insulation, compressive strength and the pore content mechanism. The experimental R 2 values obtained from the correlation between pore contents and thermal conductivity coefficient offer an understanding of the improved insulation mechanism. This trend is further investigated in the study performed by Bostanci ( 2022 ). As seen in Fig. 11 .a and 11.b, good linear correlations between the 100–1000 nm and 3–10 nm specific pore fractions. The thermal conductivity values were determined with correlation coefficients of R 2 ranging from 0.91 to 0.93. The incorporation of KP fiber led to the production of a modified pore structure with a higher amount of gel pores, despite the measurement indicating lower average pore diameters. This modification significantly contributed to the improvement of the insulating aim. Furthermore, in terms of the involved KP fiber loading, the presence of pores within the size range of 100–1000 nm was revealed to be an accurate measure for predicting compressive strength values, with an R 2 value of 0.86. Similarly, when investigating the main impact of gel pore formation in the samples containing KP, a more significant relationship between the content of pores ranging from 3–10 nm and compressive strength was observed with an R 2 value of 0.95. The experimental results highlight that a reduced amount of KP fiber significantly impacts the insulating properties of the samples due to the predicted mechanism of strength-conductivity through a changing pore structure. However, similar to the H 2 O 2 curing group, in the scope of measured MIP characteristics and pore fractions no remarkable relationship was registered. At this point, it can be said that regardless of subjected curing conditions CC fiber leads to a modified unique pore structure where the insulation-strength mechanism cannot be explained by only pore diameters. 3.5. SEM analysis Figure 12 and Fig. 13 depict the microstructural morphology of concrete samples including KP and CC fibers. The images show how the fiber content in the concrete mixtures affects the microstructure, under the curing conditions of H 2 O 2 and NaClO. SEM images demonstrate the impact of fiber particles on the alteration of pores in the cement. The S-0 sample exhibited a minimum total porosity of 8.91% and 8.59%, as well as a minimum total pore area of 3.19 m 2 /g and 2.10 m 2 /g under the H 2 O 2 and NaClO curing conditions, respectively. The addition of a little amount of KP and CC fiber to the concrete mixtures resulted in an increase in both the overall porosity and the total pore area values of all samples. The incorporation of KP into the mixtures resulted in an approximate doubling of the total pore area for all content ratios compared to the control case when samples were cured in H 2 O 2 . However, in the case of KP and CC fiber-containing mixtures, the total pore area significantly increased by a range of 3.4–6.1 times under the NaClO curing condition. In accordance with MIP results for samples cured in H 2 O 2 , the highest total porosity value was observed in both KP and CC fiber-containing mixtures at 0.5% content rate. The SEM images of KP-0.5 and CC-0.5 clearly showed entrapped air bubbles when the concrete mixtures had a reduced fiber content. Similarly, by MIP results for samples cured in NaClO, the air bubbles formed in KP-1.5 and CC-1 fiber-containing mixtures with the highest total porosity were also clearly visible in the SEM images. When fiber particles are incorporated into the cement matrix, it is expected that their inclusion will increase the overall void content of the cement matrix and voids will form around the ITZs where the fibers are positioned in the matrix due to poor adhesion (Ng et al. 2015 ; Donnini et al. 2018 ; Bostanci 2021 ). Accordingly, it can be emphasized that the microstructural morphology of KP and CC-incorporated concrete mixtures showed good conformity with the MIP test results. Furthermore, an SEM investigation is conducted to examine the behavior of the modified cement matrix, as well as the ITZs between the aggregate and fiber cement matrix. SEM analysis also indicates the formed bond structure effective on strength development between the fiber and the matrix, called C-S-H (Varghese and Unnikrishnan 2023 ). The quantity of C-S-H bonds is an excellent indicator of compressive strength development. The presence of additional C-S-H bonds enhances the compressive strength when compared to a casing without fiber. Hence, the quantity of C-S-H bonds is enhanced in the concrete mixtures with higher compressive strengths (Bostanci 2020b ; Yu et al. 2022 ; Prasad et al. 2023 ). Some previous studies have also indicated that the structure of the C-S-H gel enhances the mechanical characteristics of concrete (Yu et al. 2022 ; Prasad et al. 2023 ; Punurai et al. 2018). Moreover, as compared to a fiber-free case, the presence of additional C-S-H bonds enhances the compressive strength. However, at higher ratios of fiber content, the compressive strength gain may be hindered by the production of larger voids (Bostanci 2020b ). The SEM images clearly showed a higher amount of C-S-H bonds and the highest compressive strength in the samples cured with both H 2 O 2 and NaClO, particularly in the absence of fibers. 4. Conclusions The influence of KP and CC fiber inclusion on the mechanical, thermal insulation, pore structure and microstructure morphology of concrete samples under water, H 2 O 2 and NaClO curing conditions is investigated experimentally in this work. It is possible to infer the following conclusion: The thermal conductivity coefficient of concrete at 28 days of curing age for all curing groups revealed a pattern that the larger the amount of both KP and CC fiber, the lower the thermal conductivity coefficient. Since the fiber-related change in pore structure is the cause of the increase in thermal insulation values, the increased void formation caused by the insulation improvement also resulted in the expected limited declines in compressive strength values in proportion to increasing fiber content. A remarkable insulation gain of up to 17.80% could be detected even with the utilization of a small amount of KP fiber at a content of 0.5% in the H 2 O 2 curing group. Based on the detected pore modification effect in the H 2 O 2 curing group, a maximum of 24.31% enhancement in thermal insulation was achieved with a 10.6% strength loss in the case of 1.5% CC fiber inclusion. Meanwhile, a maximum of 22.26% conductivity reduction with a 12.99% strength decrease was detected in the same curing group and the same fiber amount for the KP fiber inclusion case. In the NaClO curing group, a maximum of 23.55% enhancement in thermal insulation was achieved with a 10.97% strength loss in the case of 1.5% CC fiber inclusion. Similarly, a maximum of 21.01% insulation enhancement with an 11.73% strength reduction was detected in the same curing group and the same fiber amount for the KP fiber inclusion case. KP fiber inclusion leads to a significant modification in gel pores and medium capillary pores for both H 2 O 2 and NaClO curing cases. Hence, strong linear correlations were found, with R 2 values of 0.92 and 0.93 for the H 2 O 2 and NaClO curing cases, respectively, between the thermal insulation and pore contents in the size range of 100–1000 nm and 3–10 nm. While the addition of KP fibers into the cementitious matrix leads to a remarkable pore modification effect by the proper amount of critical pore contents with the increasing amount of fiber, CC fiber incorporation did not provide a similar effect. At this point, it can be said that regardless of subjected curing conditions, CC fiber leads to a modified pore structure where the proper strength-insulation mechanism from the point of thermal insulation purpose cannot be predicted by only gauged contents or pore diameters. This experimental investigation utilized kapok and coconut fiber, which are considered significant sources of raw materials in recent years. The use of these natural fibers is important in terms of sustainability today. The study specifically examined the impact of adding a small amount of KP and CC fibers to concrete samples, which helped to gain a comprehensive understanding of the strength-insulation mechanism in concrete mixtures for thermal insulation purposes. In order to promote sustainable development in the building sector, incorporating a small amount of these natural fibers into concrete mixtures appears to be a useful design strategy. However, when it comes to CC fiber loading, the pore size determined for the changed pore structure resulting from CC incorporation was insufficient to fully elucidate the insulating strength mechanism in CC-incorporated samples. Therefore, further pore structure analysis revealing pore shape, connectivity, and unaccessible pores above the concept of MIP is required to reveal the strength-thermal insulation mechanism of porous concrete matrix containing CC fiber. To the best of our knowledge, within the limits of pore size distribution analysis, this is the first attempt to systematically investigate the strength-thermal insulation mechanism of the KP fiber inclusion case in cement-based mixtures. Declarations Author contribution All authors contributed to the study’s conception and design. Material preparation, data collection and analysis were performed by Gulsah Susurluk, Hakan Sarıkaya and Levent Bostancı. The first draft of the manuscript was written by Gulsah Susurluk and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Funding No funding was obtained for this study. Ethical approval and consent for publication Not applicable. Consent to participate Not applicable. Competing interests The authors declare no competing interests. References Althoey F, Ansari WS, Sufian M, Deifalla AF 2023) Advancements in low-carbon concrete as a construction material for the sustainable built environment. Developments in the Built Environment, 16, 100284. ASTM C1113/C1113-09 (2009) Standard test method for thermal conductivity of refractories by hot wire (Platinum Resistance Thermometer Technique). ASTM International, West Conshohocken, PA. Avubothu M, Ponaganti S, Sunkari R, Ganta M (2022) Effect of high temperature on coconut fiber Reinforced concrete. Materials Today: Proceedings, 55, 1197–1200. 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Zheng YA, Wang JT, Wang AQ (2021) Recent advances in the potential applications of hollow kapok fiber-based functional materials. Cellulose. 28:5269–5292. Cite Share Download PDF Status: Published Journal Publication published 18 Oct, 2024 Read the published version in Environmental Science and Pollution Research → Version 1 posted Editorial decision: Major Revision 21 Jun, 2024 Reviewers agreed at journal 11 Apr, 2024 Reviewers invited by journal 11 Apr, 2024 Editor invited by journal 03 Apr, 2024 Editor assigned by journal 20 Mar, 2024 First submitted to journal 18 Mar, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4099400","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":290031698,"identity":"eb61c94f-1974-4414-88de-5387b5f6f917","order_by":0,"name":"Gulsah 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18:50:50","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":16106,"visible":true,"origin":"","legend":"\u003cp\u003eThermal conductivity coefficients test results of CC-incorporated concrete samples\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4099400/v1/6fe36a4c6a9161d026994ea5.png"},{"id":55003581,"identity":"499cdb51-e537-433a-9389-a1cd2e81e0e0","added_by":"auto","created_at":"2024-04-19 18:42:49","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":51905,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing condition on pore properties a) Relationship between the cumulative pore volume and the pore size diameters (PSD) b) Content of pores in KP-incorporated concrete samples c) Content of pores in CC-incorporated concrete samples\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4099400/v1/3d130bfb7241a1084dde41e5.png"},{"id":55000117,"identity":"ab0ed564-7c7c-47cc-a9f9-8d18e652f0f0","added_by":"auto","created_at":"2024-04-19 18:34:49","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":59280,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of NaClO curing condition on pore properties a) Relationship between the cumulative pore volume and the pore size diameters (PSD) b) Content of pores in KP-incorporated concrete samples c) Content of pores in CC-incorporated concrete samples\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4099400/v1/276e15a30f7f4d7515797cd7.png"},{"id":55000124,"identity":"fb1a54d0-1fa1-44a9-ac28-825b72008132","added_by":"auto","created_at":"2024-04-19 18:34:50","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":47792,"visible":true,"origin":"","legend":"\u003cp\u003eThe correlation between contents of pores - thermal conductivity - strength under H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing condition a) KP-incorporated concrete samples b) CC-incorporated concrete samples\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4099400/v1/bef69c6c3d620ef3057e7586.png"},{"id":55003584,"identity":"68c61803-9912-424b-a9a7-5459ac3b800d","added_by":"auto","created_at":"2024-04-19 18:42:50","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":37018,"visible":true,"origin":"","legend":"\u003cp\u003eThe correlation between the contents of pores - thermal conductivity - strength under H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing condition a) The correlation between thermal conductivity and content of pores within the size range of 100-1000 nm in KP-incorporated concrete samples b) The correlation between thermal conductivity and content of pores within the size range of 3-10 nm in KP-incorporated concrete samples c) The correlation between strength and content of pores within the size range of 100-1000 nm in KP-incorporated concrete samples d) The correlation between strength and content of pores within the size range of 3-10 nm in KP-incorporated concrete samples\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4099400/v1/e7e2a3faac5be8b03f647483.png"},{"id":55000121,"identity":"720940f2-1a32-46d0-8a06-83b166bf0a15","added_by":"auto","created_at":"2024-04-19 18:34:49","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":45329,"visible":true,"origin":"","legend":"\u003cp\u003eThe correlation between contents of pores - thermal conductivity - strength under NaClO curing condition a) KP-incorporated concrete samples b) CC-incorporated concrete samples\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-4099400/v1/623cf0c47eea6310d4cf46d3.png"},{"id":55000123,"identity":"ea5ad165-6c16-4927-a761-0e668640a341","added_by":"auto","created_at":"2024-04-19 18:34:50","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":45039,"visible":true,"origin":"","legend":"\u003cp\u003eThe correlation between contents of pores - thermal conductivity - strength under NaClO curing condition a) The correlation between thermal conductivity and content of pores within the size range of 100-1000 nm in KP-incorporated concrete samples b) The correlation between thermal conductivity and content of pores within the size range of 3-10 nm in KP-incorporated concrete samples c) The correlation between strength and content of pores within the size range of 100-1000 nm in KP-incorporated concrete samples d) The correlation between strength and content of pores within the size range of 3-10 nm in KP-incorporated concrete samples\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-4099400/v1/aa0bd4b7d01d3dfb9d63f8f3.png"},{"id":55000126,"identity":"9060079a-b1d3-4c7d-9fcd-363aa722c567","added_by":"auto","created_at":"2024-04-19 18:34:50","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":636251,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of KP and CC fiber-incorporated concrete samples under the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2 \u003c/sub\u003ecuring condition\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-4099400/v1/e5a942449784a81eeda4b47a.png"},{"id":55000125,"identity":"7b4abfe2-3978-4ee8-8476-9983779e72eb","added_by":"auto","created_at":"2024-04-19 18:34:50","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":607091,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of KP and CC fiber-incorporated concrete samples under the NaClO curing condition\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-4099400/v1/e4b6931bd6f7b7a42a4bca1b.png"},{"id":67148899,"identity":"547e387d-7a61-4a3b-9651-14ff10ec45c5","added_by":"auto","created_at":"2024-10-21 16:09:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2552767,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4099400/v1/e05f0c3b-6624-46ba-8ed7-28717888e5cb.pdf"}],"financialInterests":"","formattedTitle":"Utilization of Natural Kapok and Coconut Fiber in Thermally Insulated Sustainable Concrete Design","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eConventional concrete manufacture substantially makes a significant to CO\u003csub\u003e2\u003c/sub\u003e emissions because of the high energy needed to generate Portland cement, the main binder of concrete (Kahan et al. 2023; Althoey et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Recent searches have stated that roughly 0.9 tonnes of CO\u003csub\u003e2\u003c/sub\u003e are released while manufacturing 1 ton of Portland cement, which accounts for approximately 5% of the human-induced CO\u003csub\u003e2\u003c/sub\u003e emissions globally (Althoey et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Nassar et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Therefore, in recent years, a vast majority of researchers have searched for sustainable resources for environmentally friendly cement and concrete, to decrease CO\u003csub\u003e2\u003c/sub\u003e emissions. Due to a substantial surge in the demand for sustainable concrete, which is one of the most extensively utilized construction materials globally (Althoey et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eConcrete is a material that is fragile and has a low ability to withstand tension and strain. When randomly dispersed natural fibers with high technical specifications are utilized to reinforce the matrix (mortar and concrete), a graded increment in tensile strength and tensile strain capacity is determined (Avubothu et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Riza et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Sarikaya and Susurluk \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Fibers interchange the action of the matrix (mortar and concrete) when cracks form and the ability of fiber-containing concrete to prevent cracks, especially microcracks, is widely known (Avubothu et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Riza et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These weaknesses of concrete can be improved by incorporating fibers, especially natural renewable fibers which are recently gaining attention with the aim of sustainable design in the construction industry (Riza et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Hence, renewable fibers such as kapok and coconut from natural fibers have increasingly been investigated in the fiber-incorporated sustainable concrete design (Damfeu et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eKapok fiber is a type of natural fiber made up of single-celled fibers, similar to cotton fiber. Nevertheless, it possesses a density of 0.29 g/ cm\u003csup\u003e3\u003c/sup\u003e, which is seven times lower than that of cotton fiber (Damfeu et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Kapok fiber has the highest void ratio of any fiber type, around 90% (Sun et al. 2023; Yang et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Nevertheless, it has a buoyancy that may be twenty times its weight (Damfeu et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) and displays better thermal properties and performance compared to the most used other kinds of natural fibers in concrete mixtures (Gobalakrishnan and Saravanan \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). This gives the kapok fiber outstanding characteristics of thermal insulation, sound insulation, and extraordinary buoyancy (Sun et al. 2023; Cao et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Conventionally, kapok fibers were commonly used for filling water safety equipment, stuffing bedding and upholstery, and providing fabric insulation (Zheng et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Yeo et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Liu et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). They also have extensive potential applications as materials for oil absorption and soundproofing (Sun et al. 2023; Liu et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Nevertheless, there is a scarcity of information regarding its application in concrete mixtures, and its performance in terms of serviceability remains unexplored.\u003c/p\u003e \u003cp\u003eCoconut fiber has also low density and mass such as the kapok fiber mentioned above. However, since coconut fiber causes less pollution during the formation phase, health hazards are minimized and it is also environmentally friendly (Nawab et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In comparison to the utilization of Kapok fiber in sustainable concrete design, coconut fibers are widely utilized as reinforcing material in construction technology (Damfeu et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). For the first time, a cement composite containing coconut fiber was produced in Thailand and used as a roof covering to both decrease heat transfer mechanisms and enhance energy savings (Gupta and Kumar \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Mintorogo et al. (2015) utilized coconut fibers in this study to increase thermal insulation and reduce energy consumption in concrete slab roof coverings. As a result of the study, it was reported that the savings achieved in roof surface thermal insulation with coconut fibers differed by 13\u0026deg;C compared to traditional reinforced concrete containing zero fiber contribution slab roofing and the reduction in energy consumption was approximately 3% (average) and 9% (maximum). Edgar et al. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) evaluated the effective use of mortars modified with coconut fibers as facade cladding layers to increase thermal comfort in building structures. Thermal properties of coconut fiber-incorporated mortars were also investigated by monitoring temperature and humidity changes as the study continued. Results show that there is an effective to enhance the thermal insulation in building structures with coconut fiber-incorporated mortars. Avubothu et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) investigated the durability properties of coconut fiber-incorporated concrete under high-temperature conditions. Based on the reported results, major enhancements were determined on the properties of coconut-incorporated concrete compared to conventional concrete under high-temperature conditions. Ali et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) reported that the mechanical features of coconut fiber-incorporated concrete varied depending on the content and length of fibers in mixtures. In their experimental study, coconut fibers with lengths of 25, 50 and 75 mm were incorporated into the mixtures at contents of 1%, 2%, 3% and 5%, by weight of cement. According to the experimental study, it was reported that coconut-incorporated concrete with a fiber length of 50 mm and a fiber content of 5% shows superior mechanical features compared to fiber-free cases. Bijo and Unnikrishnan (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) investigated the mechanical properties and impact resistance of coconut and polypropylene fiber-incorporated concrete. From the experimental study, it was observed that the maximum improvement in impact strength of coconut fiber-incorporated concrete was 94% when the fiber length was 50 mm and 134% when the fiber length of polypropylene fiber-incorporated concrete was 12 mm. Varghese and Unnikrishnan (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) examined the impression of coconut fiber addition on the mechanical features of concrete samples. Fibers with lengths of 25, 50 and 75 mm were incorporated into the mixtures at contents up to 2%, by weight of cement. According to the experimental results, it was detected that coconut fiber incorporation deeply enhanced the mechanical properties of samples, especially up to 30% improvement in shear strength properties was determined for both fiber inclusion cases of 50 mm and 75 mm. Nawab et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) studied a study on improving the effect of coconut fiber-incorporated mortars containing silica fume and metakaolin. The findings of this study demonstrate the beneficial effects of adding coconut fiber to calcium-silicate-based mixtures. This addition improves the thermal insulation and mechanical properties of samples that contain industrial by-products. The results also offer valuable information for creating environmentally friendly and high-performing cement-based materials.\u003c/p\u003e \u003cp\u003eToday, sustainability regulations in the construction industry aim to promote sustainability by encouraging the use of industrial by-products and natural resources in the design of cement-based materials, and most previous research has focused on these topics (Mwaikambo and Bisanda \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Xu et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMoreover, in recent years, with the introduction of the concept of sustainability into industrial life and the transfer of this awareness to consumers, the search for contributing to a sustainable future has begun in the construction industry, as in all industrial areas. Kapok and especially coconut fibers have also become widely investigated sustainable materials in recent years due to their renewable, biodegradable and reusable features. Nowadays, when regenerable alternative green sources are attracting more caution under sustainability targets, kapok and coconut fibers are pointed out as substantial resources of raw materials due to their great potential in sustainable cement-based material design.\u003c/p\u003e \u003cp\u003eThe increasing number of recently conducted studies analyzing the inclusion of coconut fibers into cement-based materials to enhance their mechanical and thermal insulation properties, as well as the results obtained from this study, is worthy of attention due to the implemented comparative H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing conditions. Moreover, the motivation for this manuscript is based on the utilization of kapok fiber in cement-based mixtures as a unique kind of natural fiber used for the first time, indicating a great potential for the design of eco-friendly cement-based material as a valuable sustainable resource.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n\u003ch2\u003e2.1. Materials\u003c/h2\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\n\u003cp\u003eThis study aimed to achieve a sustainable target by incorporating kapok and coco fibers into concrete mixtures manufactured according to the TS EN 206\u0026thinsp;+\u0026thinsp;A2 standard (2021). Afyon Cement provides Ordinary Portland Cement (OPC) of 42.5 R type, which adheres to the TS EN 196-1 standard and is utilized in concrete compositions (2019). The concrete mixtures were made using tap water sourced from the city waterworks and aggregates supplied by Oktaş Concrete.\u003c/p\u003e\n\u003cp\u003eThe chemical compositions and physical properties of used cement and aggregate are presented in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The physical and mechanical properties of kapok and coconut fibers incorporated into the concrete mixtures are also shown in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n\u003ctable border=\"1\" width=\"68%\"\u003e\u003ccaption\u003e\n\u003cp\u003eTable 1\u003c/p\u003e\n\u003cp\u003eChemical compositions and physical properties of used cement and aggregate.\u003c/p\u003e\n\u003c/caption\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"52%\"\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"29%\"\u003e\n\u003cp\u003e\u003cstrong\u003eCement\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e\u003cstrong\u003eAggregate\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"52%\"\u003e\n\u003cp\u003e\u003cu\u003eChemical composition (wt/wt %)\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3 \u003c/sub\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCaO\u003c/p\u003e\n\u003cp\u003eMgO\u003c/p\u003e\n\u003cp\u003eSO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003eNa\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n\u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n\u003cp\u003eCl \u003csup\u003e-\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eLoss on ignition\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cu\u003ePhysical properties\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003eDensity (g/cm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n\u003cp\u003eSpecific surface area (cm\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e\n\u003cp\u003e\u003csub\u003e\u0026nbsp;\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"29%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e19.1\u003c/p\u003e\n\u003cp\u003e5.19\u003c/p\u003e\n\u003cp\u003e2.65\u003c/p\u003e\n\u003cp\u003e63.4\u003c/p\u003e\n\u003cp\u003e1.83\u003c/p\u003e\n\u003cp\u003e2.95\u003c/p\u003e\n\u003cp\u003e0.22\u003c/p\u003e\n\u003cp\u003e0.94\u003c/p\u003e\n\u003cp\u003e0.01\u003c/p\u003e\n\u003cp\u003e3.06\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e1.05 \u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e20.9\u003c/p\u003e\n\u003cp\u003e0.4\u003c/p\u003e\n\u003cp\u003e0.2\u003c/p\u003e\n\u003cp\u003e42.6\u003c/p\u003e\n\u003cp\u003e0.4\u003c/p\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003cp\u003e\u0026lt;0.1\u003c/p\u003e\n\u003cp\u003e0.1\u003c/p\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e2.41\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eThe physical and mechanical properties of kapok and coconut fibers\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eKapok fiber\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eCoconut fiber\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cspan class=\"Underline\"\u003ePhysical properties\u003c/span\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDensity (gr/cm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.29\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.2\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eMoisture (%)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLength (mm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e8\u0026ndash;35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e20\u0026ndash;150\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDiameter (\u0026micro;m)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e20\u0026ndash;43\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100\u0026ndash;450\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cspan class=\"Underline\"\u003eMechanical properties\u003c/span\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTensile strength (N/mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e189\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e105\u0026ndash;175\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eInitial modules (GPa)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4\u0026ndash;11\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.6\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n\u003ch2\u003e2.2. Mix proportions\u003c/h2\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\n\u003cp\u003eIn order to investigate the impact of adding kapok fiber (KP) and coconut fiber (CC) on the mechanical properties, thermal conductivity, pore structure, and microstructure morphology of concrete samples, we prepared seven different concrete mixtures. For this purpose, KP and CC were utilized in the concrete mixtures at contents of 0.5%, 1% and 1.5%, by weight of cement. In all mixtures the total amount of cement was kept constant. Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e tabulates the mix ratios of the concrete samples produced. There was a total of seven mixtures, which were labeled as S-0, KP-0.5, KP-1, KP-1.5, CC-0.5, CC-1, and CC-1.5. The samples were labeled with representing the S-0 without kapok fiber or coconut fiber, KP with kapok fiber and CC with coconut fiber content. The latter labels \u0026ldquo;0\u0026rdquo;, \u0026ldquo;0.5\u0026rdquo;, \u0026ldquo;1\u0026rdquo;, and \u0026ldquo;1.5\u0026rdquo; indicate the amount of fiber added to the concrete mixture in percentage.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab3\" style=\"width: 545px;\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eConcrete mixture proportions used in the study\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth style=\"width: 69px;\" align=\"left\"\u003e\n\u003cp\u003eMix\u003c/p\u003e\n\u003c/th\u003e\n\u003cth style=\"width: 50.5312px;\" align=\"left\"\u003e\n\u003cp\u003eCement\u003c/p\u003e\n\u003cp\u003e(kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth style=\"width: 61.4688px;\" align=\"left\"\u003e\n\u003cp\u003eFine aggregate\u003c/p\u003e\n\u003cp\u003e(kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth style=\"width: 108px;\" align=\"left\"\u003e\n\u003cp\u003eCoarse aggregate\u003c/p\u003e\n\u003cp\u003e(kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth style=\"width: 71px;\" align=\"left\"\u003e\n\u003cp\u003eKapok fiber\u003c/p\u003e\n\u003cp\u003e(gr)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth style=\"width: 82px;\" align=\"left\"\u003e\n\u003cp\u003eCoconut fiber\u003c/p\u003e\n\u003cp\u003e(gr)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth style=\"width: 52px;\" align=\"left\"\u003e\n\u003cp\u003eWater\u003c/p\u003e\n\u003cp\u003e(kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 69px;\" align=\"left\"\u003e\n\u003cp\u003eS-0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 50.5312px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e300\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 61.4688px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e722\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 108px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e1111\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 71px;\" align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 82px;\" align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 52px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e160\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 69px;\" align=\"left\"\u003e\n\u003cp\u003eKP-0.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 50.5312px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e300\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 61.4688px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e722\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 108px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e1111\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 71px;\" align=\"left\"\u003e\n\u003cp\u003e15\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 82px;\" align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 52px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e160\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 69px;\" align=\"left\"\u003e\n\u003cp\u003eKP-1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 50.5312px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e300\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 61.4688px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e722\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 108px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e1111\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 71px;\" align=\"left\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 82px;\" align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 52px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e160\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 69px;\" align=\"left\"\u003e\n\u003cp\u003eKP-1.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 50.5312px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e300\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 61.4688px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e722\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 108px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e1111\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 71px;\" align=\"left\"\u003e\n\u003cp\u003e45\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 82px;\" align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 52px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e160\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 69px;\" align=\"left\"\u003e\n\u003cp\u003eCC-0.5\u003c/p\u003e\n\u003cp\u003eCC-1\u003c/p\u003e\n\u003cp\u003eCC-1.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 50.5312px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e300\u003c/p\u003e\n\u003cp\u003e300\u003c/p\u003e\n\u003cp\u003e300\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 61.4688px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e722\u003c/p\u003e\n\u003cp\u003e722\u003c/p\u003e\n\u003cp\u003e722\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 108px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e1111\u003c/p\u003e\n\u003cp\u003e1111\u003c/p\u003e\n\u003cp\u003e1111\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 71px;\" align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 82px;\" align=\"left\"\u003e\n\u003cp\u003e15\u003c/p\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003cp\u003e45\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"width: 52px;\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e160\u003c/p\u003e\n\u003cp\u003e160\u003c/p\u003e\n\u003cp\u003e160\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n\u003ch2\u003e2.3. Sample preparation, curing conditions and testing procedures\u003c/h2\u003e\n\u003cp\u003eThe concrete mixes were blended using a mechanical mixer in the experimental experiments and then poured into cube molds measuring 100 mm x 100 mm x 100 mm. During the preparation of the mixtures, mixing was carried out with the help of a vertical-axis mixer. Water was incrementally introduced into the mixtures until a uniform matrix was obtained. Tap water was used as the mixing water. When the concrete reached a specific consistency, fibers were added. Then, the concrete mixtures were poured into the usual cube molds and subjected to vibration to improve the consistency of the samples. A total of ten concrete samples were manufactured from each concrete mixture in order to conduct tests on strength, pore structure, thermal conductivity coefficient, and microstructure morphology. The concrete samples were stored in the mold at a temperature of 21\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u0026deg;C for the first 24-hour period. The samples were extracted from the mold the following day and underwent three distinct curing cases, including conventional water, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing regimes, for a duration of 28 days till the testing period. A set of samples was immersed in water at room temperature of 21\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u0026deg;C. In the second curing group, a 5% H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e solution in water was prepared. The specimens in the second group were then submerged in this solution. Similarly, a 5% NaClO solution in water was prepared for the remaining curing process. In both curing regimes of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO, the curing process was performed in the form of water curing method. The cured samples were subjected to tests to assess their compressive strength and thermal conductivity coefficient. Compressive strength, pore structure, thermal conductivity coefficient and microstructure morphology tests were subjected on the samples under curing conditions containing H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO, respectively. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e presents the implemented test program.\u003c/p\u003e\n\u003cp\u003eConcrete samples measuring 100 x 100 x 100 mm underwent compressive strength tests. The compressive strengths were established by calculating the mean of three separate test results in accordance with the TS EN 12390-4 standard (2002).\u003c/p\u003e\n\u003cp\u003eThe remaining mixture samples that were not tested for strength were utilized to calculate the thermal conductivity coefficients and conduct mercury intrusion porosimetry (MIP) experiments on fiber-containing concrete mixtures. The thermal conductivity coefficient of the samples was measured using the ASTM C 1113-09 hot wire standard (2009). The thermal conductivity coefficient of each sample was tested five times for various locations using a QTM-500 device. The resulting values were averaged to obtain the final measurement. The mercury intrusion porosimetry test was utilized to determine the pore structure characteristics of the concrete samples, including total porosity, pore diameter sizes, and specific pore contents. The MPI test was assessed utilizing a QTM-500 device. The device is capable of detecting pore widths ranging from 3 to 360 micrometers.\u003c/p\u003e\n\u003cp\u003eThe microstructure morphology of the remaining specimens from the 28-day compressive strength test was determined using SEM (Scanning Electron Microscope) analysis. The powder form of sample pieces, which were precisely taken from the fracture surface of the compressive strength test, were coated with carbon and made suitable for microstructure analysis. SEM analyses were performed with the LEO 1430 VP model SEM device.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results and discussions","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n\u003ch2\u003e3.1. Compressive strength test results\u003c/h2\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e illustrates the 28-day strength test for concrete samples containing KP fiber under three different curing conditions.\u003c/p\u003e\n\u003cp\u003eThe water group control sample achieved a strength of 49.76 MPa after a curing period of 28 days. The addition of KP to the concrete mixtures at content ratios of 0.5%, 1%, and 1.5% resulted in decreases in compressive strength of 6.45%, 9.12%, and 9.54%, respectively. The control sample of the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e group reached a strength of 47.25 MPa at 28 days of age. KP incorporation at 0.5%, 1% and 1.5% content ratios led to decreases in compressive strength by 10%, 12.84% and 12.99%, respectively. The NaClO group control sample reached a compressive strength of 45.18 MPa after a curing period of 28 days. For the fiber additions of the 0.5%, 1% and 1.5% fiber addition, the compressive strength decreases, which are 10.9%, 11.5%, and 11.73%, respectively. As seen in all curing groups, the strength of concrete at 28 curing age showed a trend that the higher the KP incorporation ratio, the lower the compressive strength.\u003c/p\u003e\n\u003cp\u003eAll mixture samples exhibited the highest compressive strengths when subjected to water-curing conditions with identical KP contents. Conversely, the samples exposed to NAClO curing conditions displayed the lowest compressive strengths. Incorporation of KP into the concrete mixtures even at a minimum content leads to a less strong matrix and diminishes the bonding mechanism between the interfacial transition zone (ITZs) of the fiber and cement matrix. As seen at higher KP contents even the reduction in strength tendency was observed, the decreases were limited such as 3.30%, 3.29%, 0.91% levels for water, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing groups, respectively.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e displays the results of a 28-day strength test of CC-incorporated concrete samples under three different curing conditions.\u003c/p\u003e\n\u003cp\u003eAt 28 days old, the control sample with no fiber content obtained a compressive strength of 49.76 MPa. CC incorporation into the concrete mixtures at 0.5%, 1% and 1.5% content ratios led to reductions in strength by 5.52%, 6.43% and 8.46%, respectively. The compressive strength of the control sample in the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e group was determined to be 47.25 MPa after 28 days. In the case of the 0.5%, 1% and 1.5% content, the compressive strength decreases, which were 8.97%, 9.98%, and 10.6% respectively. The control sample from the NaClO group had a strength of 45.18 MPa after 28 days. On the other hand, in the 0.5%, 1% and 1.5% content mixtures, the reductions in compressive strength values were 9.22%, 10.33% and 10.97%, respectively. As seen in all curing groups, the compressive strength of concrete at 28 days of curing showed a consistent trend: the greater the CC incorporation ratio, the lower the compressive strength. This finding emphasizes the crucial impact of the ratio of CC fiber content on the compressive strength of concrete (Nawab et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e; Ali et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e), underlining the need of adjusting the fiber content to reduce strength reduction. Similar to the KP-incorporated fiber samples, the samples incorporated with CC also showed that the highest compressive strengths were achieved in samples cured with water, whereas the lowest strengths were observed in samples subjected to NAClO curing conditions, regardless of the CC content. Incorporation of CC into the concrete mixtures even at a minimum content leads to a less strong matrix and reduces the bonding mechanism between the ITZs of the fiber and cement matrix. As seen at higher CC contents even though the reductions in strength were observed, the decreases were limited such as 3.1%, 1.79%, and 1.92% levels for water, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing groups, respectively.\u003c/p\u003e\n\u003cp\u003eKPs and CCs with a lower density results in the formation of additional voids in the matrix. When cement modification was performed via KP and CC fiber at a content of 0.5%, there may not be a dominant modification in the fiber cement ITZs due to the fiber content increasing from 0.5\u0026ndash;1% and 1.5%. This is shown with compressive strength results derived from all curing groups, indicating that the %0.5 fiber addition is critical (Varghese and Unnikrishnan \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e; Haigh et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). These phenomena may indicate a great potential for superior KP and CC-incorporated concrete properties for higher KP and CC incorporation cases such as an enhanced insulation target under a limited strength reduction.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n\u003ch2\u003e3.2. Thermal conductivity test results\u003c/h2\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e illustrates the influence including KP on the thermal insulation efficiency of KK-incorporated concrete samples at 28-days for the three different curing conditions.\u003c/p\u003e\n\u003cp\u003eThe thermal conductivity coefficients of the KP-incorporated concrete mixtures ranged from 2.18 to 2.96 W/mK. As presented in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e, the water control group sample had a thermal conductivity value of 2.96 W/mK after 28 days of curing. The thermal conductivity coefficient decreased by 13.85%, 17.22%, and 21.28% for KP contents of 0.5%, 1%, and 1.5%, respectively. The thermal conductivity coefficient of the control sample in the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e group was measured to be 2.92 W/mK. In the case of 0.5%, 1% and 1.5% KP containing, the decreases were 16.09%, 17.8% and 22.26% in mixtures, respectively. The NaClO group control sample achieved a thermal conductivity coefficient of 2.76 W/mK. On the other hand, in the 0.5%, 1% and 1.5% fiber-containing mixtures, the reductions in thermal conductivity coefficient values were 14.49%, 16.3% and 21.01%, respectively. When considering all curing groups, it was observed that the thermal conductivity coefficient of concrete decreased as the KP incorporation ratio increased at 28 curing age. The addition of KP into the concrete mixtures even at a minimum content led to causes lower conductivity values. Thus, the addition of KP into the concrete mixtures even at a minimum content leads to a less strong matrix and reduces the bonding mechanism between the ITZs of the fiber and cement matrix. Accordingly, at higher KP contents even though the reduction in the thermal conductivity tendency was observed, the declines were limited such as 8.62%, 7.34%, 7.62% levels for water, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing groups, respectively.\u003c/p\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\n\u003cp\u003eThe thermal conductivity coefficients of the CC-incorporated concrete samples evaluated under different curing conditions at 28 days are indicated in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cp\u003eAccording to Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e, the control sample with no fiber content had a thermal conductivity value of 2.96 W/mK at 28 days of age. Thermal conductivity coefficient decreases were found as 11.82%, 18.24% and 23.98% for 0.5%, 1% and 1.5% CC contents, respectively. Incorporating CC into the mixtures resulted in decreased conductivity levels. The thermal conductivity coefficient of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e group control sample was 2.92 W/mK. In the case of 0.5%, 1% and 1.5% CC containing, the decreases were 13.69%, 17.8% and %24.31 in mixtures, respectively. The thermal conductivity coefficient of the control sample from the NaClO group was measured to be 2.76 W/mK. On the other hand, at the 0.5%, 1% and 1.5% fiber content ratios, the decreases in thermal conductivity coefficient values were 10.5%, 17.02% and 23.55%, respectively. As far as all curing groups are concerned, the thermal conductivity coefficient of concrete at 28 curing age showed a trend that the higher the CC incorporation ratio, the lower the thermal conductivity coefficient. The addition of CC into the concrete mixtures even at a minimum content led to causes lower conductivity values. Hence, the addition of CC into the concrete mixtures even at a minimum content leads to a less strong matrix and reduces the bonding mechanism between the ITZs of the fiber and cement matrix. Thus, at higher CC contents even the reduction in thermal conductivity tendency was detected, the declines were limited such as 13.79%, 12.31%, 14.57% levels for water, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing groups, respectively.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n\u003ch2\u003e3.3. Mercury intrusion porosimetry (MIP) test results\u003c/h2\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\n\u003cp\u003eThe primary characteristics of the pore structure significantly affect the mechanical and thermal insulation capabilities of concrete. Therefore, knowledge of the main pore structure properties such as total porosity (TP), total pore area (TPA), median pore diameter-volume (MPDv), median pore diameter-area (MPDa) are valuable to evaluate the performance of concrete (Bostanci \u003cspan class=\"CitationRef\"\u003e2020a\u003c/span\u003e). Previous studies reported that fibers added into concrete mixtures improved (contribute positively to the pore structure) pore structure features of concrete samples under optimum conditions (Wang et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). The MIP was used to measure the main pore structure characteristics of 28-day concrete samples that contained KP and CC fiber. The pore structure parameters of concrete samples incorporating KP and CC fiber are listed in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab4\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eMIP test results of KP and CC-incorporated concrete samples\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eMixture\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing group\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eNaClO curing group\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTP (%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTPA (m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eMPDa (nm)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eAPD (4V/A) (nm)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTP (%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTPA (m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eMDPa (nm)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eAPD (4V/A) (nm)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eS-0\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.91\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e3.19\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e25.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e48.8\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.59\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e2.11\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e42.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e71.8\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eKP-0.5\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e11.67\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e6.64\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e17.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e31.9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e12.47\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e9.31\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e24.4\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eKP-1\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.54\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e6.07\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e24\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e11.77\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e12.24\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e17.5\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eKP-1.5\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e9.77\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e6.44\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e5.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e26.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e14.89\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e15.04\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e18.9\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eCC-0.5\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e25.86\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e2.41\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e43.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e245.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e9.54\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.51\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e19.4\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eCC-1\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e11.24\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e5.71\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e14.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e35.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e22.39\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e7.63\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e59.9\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eCC-1.5\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e7.71\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1.25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e42.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e104.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e9.49\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.04\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e20.2\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eAccording to MIP results for samples cured in H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, the addition of KP into the mixtures approximately doubled the total pore area at all KP content ratios in comparison to control case. When fibers are incorporated into the cement matrix, it is expected that voids will form around the areas where the fibers are positioned in the matrix due to poor adhesion (Ng et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e). On the other hand, the MPDa values showed a continuous decrease in direct proportion to the KP fiber content ratio. In comparison to the control sample containing zero fiber (S-0), the median pore diameter-area values of KP-incorporated concrete mixtures decreased by 31.25%, 68.35% and 77.73% respectively. Therefore, it can be said because the formation of a larger number of voids with smaller surface area diameters by fiber addition. A comparable trend was noted in the APD. In the incorporation of CC into the concrete mixtures cured in H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, similar results were observed at 0.5% and 1.5% content ratios in terms of pore properties, while a different trend was observed at 1% content ratio.\u003c/p\u003e\n\u003cp\u003eIn the NaClO curing condition, the total porosity was detected as 8.59% in the sample containing zero fiber (S-0), when both KP and CC fibers were added to the mixtures, TP values were enhanced in all mixtures. In the case of KP-containing mixtures, the TPA deeply increased in a range of 3.4\u0026ndash;6.1 times. In comparison to the S-0, the MPDa values of KP-incorporated concrete mixtures declined by 31.25%, 68.35% and 77.73% respectively. Thus, both the TPA increase and a decline in APD were observed. In the case of 0.5%, 1% and 1.5% CC addition, the TPA increased by approximately four times in the same curing condition. At 0.5% and 1.5% content ratios, similar results were observed in terms of pore properties. There was a decrease of 85.24% in the MPDa at 0.5% and 1.5% content ratios, and 88.29% decrease at %1 content ratio. Comparable trends were noted in the APD\u0026rsquo;s of samples including KP and CC fiber. To gain a more comprehensive understanding of the effect of different amounts of fiber under different curing conditions on pore properties, the pore properties were discussed in detail.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e depicts the effect of the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing condition on pore properties at 28 days. The QTM-500 device was used to evaluate the pores ranging in size from 3 to 360,000 nm, as mentioned earlier. As seen in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e.a, cumulative pore volume curves of all samples for all fiber addition cases indicate remarkable variations of the curves within the pore size ranges of 3\u0026ndash;10 nm, 10\u0026ndash;100 nm, and 100\u0026ndash;360,000 nm. Within the size range of 3\u0026ndash;10 nm, mercury exhibited a consistent and gradual drop initially. Subsequently, there is a rapid reduction in size within the range of 10\u0026ndash;100 nm, followed by a consistent decline in the size range of 100\u0026ndash;360,000 nm. As depicted in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e.a, the CC-0.5 sample containing a 0.5% content ratio exhibited the highest pore volume throughout the range of pore diameters from 3 to 360,000 nm, where the measurement was carried out, following the determined maximum porosity and maximum APD values. Similarly, the KP-0.5 sample containing a 0.5% content ratio exhibited the second-highest pore volume behavior throughout the pore diameter range of 3-100 nm.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e.b reveals the content of pores in KP-incorporated concrete samples. As it is seen, while the smallest pore content (3\u0026ndash;10 nm) formation determined in sample S-0 was 2.56%, higher pore contents in concrete samples KP-0.5, KP-1 and KP-1.5 (5.25%, 10.26% and 9.48%, respectively) were determined. This suggests that the addition of KP fiber has a notable impact on the creation of pores within the size range of 3\u0026ndash;10 nm, and a similar trend was found within the range of 10\u0026ndash;100 nm. On the other hand, in the size of 100\u0026ndash;1000 nm, the highest pore formation was found as 22.83% in the control sample and lower pore proportions were found in all KP-incorporated samples for the above-mentioned pore content. It is evident that the presence of KP fiber significantly impacted the pore structure of the samples, particularly the gel pores and small capillary pores. \u0026Ouml;z et al. indicated that an increase in fiber content leads to the creation of pores due to loose ITZs (\u0026Ouml;z et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e.c reveals the content of pores in CC-incorporated concrete samples. As depicted in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e.c, the incorporation of CC fiber into the mixtures led to a higher proportion of pores within the size range of 1000\u0026thinsp;\u0026minus;\u0026thinsp;360,000 nm. Furthermore, the addition of CC fiber caused a decrease in pore sizes within the range of 10\u0026ndash;100 nm. At this point, it is clearly said that while both KP and CC fiber dominated the pore structure of samples, the mostly affected pore sizes were reversed. In contrast to KP fiber addition, CC fiber dominated mostly large capillary pores and macro pores formation.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e indicates the effect of NaClO curing condition on pore properties at 28 days. As shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e.a, cumulative pore volume curves of all samples indicate remarkable variations of the curves within the pore size ranges of 3\u0026ndash;10 nm, 10\u0026ndash;100 nm, and 100\u0026ndash;360,000 nm. Within the size range of 3-100 nm, there is a rapid decrease in the accumulation of mercury initially, followed by a regular decline in the size range of 100\u0026ndash;360,000 nm. As depicted in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e.a, the CC-1 sample containing 1% content ratio exhibited the highest pore volume throughout the range of pore diameters from 3 to 360,000 nm, where the measurement was carried out, following the determined maximum porosity and maximum APD values. Similarly, the KP-1.5 sample containing 1.5% content ratio exhibited the second-highest pore volume behavior throughout the pore diameter range of 3-100 nm.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e.b indicates the content of pores in KP-incorporated concrete samples. As it is shown, while the highest pore content (100\u0026ndash;1000 nm) formation determined in sample S-0 was 18.87%, smaller pore contents in concrete samples KP-0.5, KP-1 and KP-1.5 (10.99%, 5.13% and 4.99%, respectively) were determined. A similar behavior is observed within the size range of 100,000-360,000 nm. Unlike, in the size of 3\u0026ndash;10 nm, the smallest pore formation was achieved in the control sample and higher pore proportions were achieved in all KP-incorporated samples for the above-mentioned pore content. At this point, it can be said that the pore structure of samples was positively affected due to the addition of KP fiber, especially gel pores. This tendency towards the formation of pores due to a loose ITZs with enhancing fiber content was indicated by \u0026Ouml;z et al. (\u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e.c indicates the content of pores in CC-incorporated concrete samples. As it is shown, while the highest pore content (100\u0026ndash;1000 nm) formation achieved in sample S-0 was 18.87%, smaller pore contents in concrete samples CC-0.5, CC-1 and CC-1.5 (5.29%, 4.82% and 7.07%, respectively) were achieved. On the other hand, the control sample exhibited the lowest pore formation, ranging from 3\u0026ndash;10 nm, compared to the samples containing KP fiber under the NaClO curing condition. Moreover, the highest pore contents are minimum for a 1.5% content level in the same curing condition for both KP and CC fiber. As an obvious result, two different fibers exhibited similar behavior in the same curing condition. The estimated pore fractions indicate that the inclusion of both CC and KP fibers results in a reduction in pore size in the cement matrix, regardless of the kind of fiber used. This effect is shown when the cement is cured in the NaClO and is particularly noticeable in the decrease of medium-sized capillary pores.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.4 Optimum fiber content, type and curing media in terms of compressive strength \u0026ndash; pore structure - insulation relationships\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n\u003ch2\u003e3.4.1. Samples under H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing condition\u003c/h2\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e depicts the impact of including KP and CC fibers on the pore structure, thermal conductivity and compressive strength characteristics of concrete samples when subjected to H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing conditions. This examination aims to enhance the comprehension of the effects of KP and CC fiber inclusion on these properties. As previously stated, the addition of 0.5%, 1% and 1.5% KP led to reductions of 16.09%, 17.8%, and 22.26% in thermal conductivity values, compared to the control sample in the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing group. In Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e.a, the results clearly indicate that thermal conductivity values decrease at a maximum content ratio of 0.5%. The decline in thermal conductivity values is attributed to the modifying pore structure related to the fibers. Thus, this decrease in conductivity also resulted in a reduction in compressive strength values. KP incorporation at 0.5%, 1% and 1.5% content ratios resulted in reductions in compressive strength by 10%, 12.84% and 12.99%, respectively. Thus, when it involves fiber loading, the thermal conductivity values indicated a reduction, whereas the reductions in compressive strength values revealed a limited trend. As previously stated, the addition of KP fiber has an important effect on the formation of pores within the size range of 3\u0026ndash;10 nm. This same trend was also observed within the range of 10\u0026ndash;100 nm. On the other hand, in the size of 100\u0026ndash;1000 nm, the highest pore formation was found as 22.83% in the control sample and lower pore proportions were found in all KP-incorporated samples for the above-mentioned pore content. At this point, the significant impact of KP fiber addition was dominant especially on gel pores and small capillary pores. As stated before, in the cases of 0.5%, 1% and 1.5% CC incorporation into mixtures, led to 13.69%, 17.8% and %24.31 decreases in thermal conductivity values and resulted in %8,97, %9,98 ve %10,6 decreases in the compressive strength values, respectively. In Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e.b, the results clearly report that thermal conductivity values decrease at a maximum content ratio of 0.5%. As seen in the KP fiber incorporation case, while the thermal conductivity values reduced, the reductions in compressive strength values showed a proper trend. In contrast to the KP fiber addition case, CC fiber dominated effectively on capillary and macro pore formation.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e presents the insulation-strength relationships of concrete samples under H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing conditions, revealing an understanding of the impact of KP fiber addition on pore contents, thermal conductivity, and compressive strength characteristics. When the change in pore proportions, thermal conductivity and strength values by the inclusion of KP fiber into concrete mixtures were examined, the detected R\u003csup\u003e2\u003c/sup\u003e values seen above indicate strong linear correlations among the thermal conductivity, compressive strength and the pore contents. The experimental R\u003csup\u003e2\u003c/sup\u003e values determined by the correlations between pore development and thermal conductivity coefficient reveal an understanding of the improved insulation process, this tendency is also indicated in the study by Bostanci (\u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). As shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e.a and 9.b, good linear correlations between the specific pore proportions within the size range of 100\u0026ndash;1000 nm and 3\u0026ndash;10 nm. The thermal conductivity measurements obtained correlation coefficients of R\u003csup\u003e2\u003c/sup\u003e ranging from 0.92 to 0.74. Despite the average pore diameters being lower, the addition of KP fiber in the matrix caused the formation of gel pores and small capillary pores, which significantly contributed to the insulation purpose. Furthermore, a significant correlation was observed between the pore content within the range of 100\u0026ndash;1000 nm and the 28-day compressive strength measurement, with an R\u003csup\u003e2\u003c/sup\u003e value of 0.97. Furthermore, an important correlation was observed between the amount of pores ranging 3\u0026ndash;10 nm and the compressive strength, with an R\u003csup\u003e2\u003c/sup\u003e value of 0.82.\u003c/p\u003e\n\u003cp\u003eThe experimental results indicate that even a small amount of KP fiber added into the concrete significantly enhances its thermal insulation ability compared to the fiber-free case. The modified KP-incorporated pore structure was effective in optimizing the desired thermal insulation with predictable strength loss. However, when CC fibers were included, the modifications in pore characteristics of the modified structure were not sufficient to completely explain the mechanism for the insulating strength in the CC-incorporated samples. Therefore, advanced analysis is required to reveal the insulation-strength mechanism of samples containing CC fiber.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n\u003ch2\u003e3.4.2. Samples under NaClO curing condition\u003c/h2\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e depicts the impact of including KP and CC fibers on the pore structure, thermal conductivity and strength characteristics of concrete samples. This investigation specifically focuses on the relationship between these variables under NaClO curing conditions.\u003c/p\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\n\u003cp\u003eAs previously mentioned, in the case of 0.5%, 1% and 1.5% KP addition, the decreases in thermal conductivity values were 14.49%, 16.3% and 21.01% in comparison to the free-fiber case in the NaClO curing group, respectively. The decrease in thermal conductivity values can be related to the modified pore structure, resulting in a limited decrease in compressive strength values. Particularly under the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing condition, the compressive strength values decreased by 10.91%, 11.5%, and 12.73%, respectively. Previous studies have indicated that the inclusion of both KP and CC fiber plays a major role in the creation of pores within the size range of 3\u0026ndash;10 nm. On the other hand, in the size of 100\u0026ndash;1000 nm, the highest pore formation was found as 18.87% in the control sample and lower pore proportions were found in all KP-incorporated samples for the above-mentioned pore content. At this point, the significant impact of KP fiber addition was especially on gel pores formation. As stated before, in the case of 0.5%, 1% and 1.5% CC incorporation into mixtures, 10.5%, 17.02% and %23.55 enhancements on thermal insulation properties were measured. As expected, respectively %9.22, %10.33 ve %10.97 reductions in the compressive strength values were also detected due to the modified pore structure of samples with lower conductivity values.\u003c/p\u003e\n\u003cp\u003eSimilar to the KP fiber inclusion case, the thermal conductivity values decreased, and the declines in compressive strength values exhibited a suitable trend. Moreover, as seen in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e.a and 10.b, the macro pore formation within size range of 10000-360,000 nm was minimum at 1.5% fiber addition both for KP and CC fiber incorporation cases under the NaClO curing condition. In fact, the utilization of both KP and CC fibers played a similar role in the formation of similar pore fractions in the same curing condition.\u003c/p\u003e\n\u003c/div\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e shows the significant correlations between the insulation-strength mechanism and the inclusion of KP fiber, specifically under the NaClO curing condition. This investigation aims to understand the impact of KP fiber on the mechanism. When the changes in the pore proportions, thermal conductivity coefficient and strength values by the inclusion of KP fiber into the cement matrix were examined, the obtained R\u003csup\u003e2\u003c/sup\u003e values reveal an effective linear correlation among the thermal insulation, compressive strength and the pore content mechanism. The experimental R\u003csup\u003e2\u003c/sup\u003e values obtained from the correlation between pore contents and thermal conductivity coefficient offer an understanding of the improved insulation mechanism. This trend is further investigated in the study performed by Bostanci (\u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). As seen in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e.a and 11.b, good linear correlations between the 100\u0026ndash;1000 nm and 3\u0026ndash;10 nm specific pore fractions. The thermal conductivity values were determined with correlation coefficients of R\u003csup\u003e2\u003c/sup\u003e ranging from 0.91 to 0.93. The incorporation of KP fiber led to the production of a modified pore structure with a higher amount of gel pores, despite the measurement indicating lower average pore diameters. This modification significantly contributed to the improvement of the insulating aim.\u003c/p\u003e\n\u003cp\u003eFurthermore, in terms of the involved KP fiber loading, the presence of pores within the size range of 100\u0026ndash;1000 nm was revealed to be an accurate measure for predicting compressive strength values, with an R\u003csup\u003e2\u003c/sup\u003e value of 0.86. Similarly, when investigating the main impact of gel pore formation in the samples containing KP, a more significant relationship between the content of pores ranging from 3\u0026ndash;10 nm and compressive strength was observed with an R\u003csup\u003e2\u003c/sup\u003e value of 0.95. The experimental results highlight that a reduced amount of KP fiber significantly impacts the insulating properties of the samples due to the predicted mechanism of strength-conductivity through a changing pore structure.\u003c/p\u003e\n\u003cp\u003eHowever, similar to the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing group, in the scope of measured MIP characteristics and pore fractions no remarkable relationship was registered. At this point, it can be said that regardless of subjected curing conditions CC fiber leads to a modified unique pore structure where the insulation-strength mechanism cannot be explained by only pore diameters.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n\u003ch2\u003e3.5. SEM analysis\u003c/h2\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e depict the microstructural morphology of concrete samples including KP and CC fibers. The images show how the fiber content in the concrete mixtures affects the microstructure, under the curing conditions of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO. SEM images demonstrate the impact of fiber particles on the alteration of pores in the cement.\u003c/p\u003e\n\u003cp\u003eThe S-0 sample exhibited a minimum total porosity of 8.91% and 8.59%, as well as a minimum total pore area of 3.19 m\u003csup\u003e2\u003c/sup\u003e/g and 2.10 m\u003csup\u003e2\u003c/sup\u003e/g under the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing conditions, respectively. The addition of a little amount of KP and CC fiber to the concrete mixtures resulted in an increase in both the overall porosity and the total pore area values of all samples. The incorporation of KP into the mixtures resulted in an approximate doubling of the total pore area for all content ratios compared to the control case when samples were cured in H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. However, in the case of KP and CC fiber-containing mixtures, the total pore area significantly increased by a range of 3.4\u0026ndash;6.1 times under the NaClO curing condition. In accordance with MIP results for samples cured in H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, the highest total porosity value was observed in both KP and CC fiber-containing mixtures at 0.5% content rate. The SEM images of KP-0.5 and CC-0.5 clearly showed entrapped air bubbles when the concrete mixtures had a reduced fiber content. Similarly, by MIP results for samples cured in NaClO, the air bubbles formed in KP-1.5 and CC-1 fiber-containing mixtures with the highest total porosity were also clearly visible in the SEM images.\u003c/p\u003e\n\u003cp\u003eWhen fiber particles are incorporated into the cement matrix, it is expected that their inclusion will increase the overall void content of the cement matrix and voids will form around the ITZs where the fibers are positioned in the matrix due to poor adhesion (Ng et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e; Donnini et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Bostanci \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). Accordingly, it can be emphasized that the microstructural morphology of KP and CC-incorporated concrete mixtures showed good conformity with the MIP test results.\u003c/p\u003e\n\u003cp\u003eFurthermore, an SEM investigation is conducted to examine the behavior of the modified cement matrix, as well as the ITZs between the aggregate and fiber cement matrix. SEM analysis also indicates the formed bond structure effective on strength development between the fiber and the matrix, called C-S-H (Varghese and Unnikrishnan \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). The quantity of C-S-H bonds is an excellent indicator of compressive strength development. The presence of additional C-S-H bonds enhances the compressive strength when compared to a casing without fiber. Hence, the quantity of C-S-H bonds is enhanced in the concrete mixtures with higher compressive strengths (Bostanci \u003cspan class=\"CitationRef\"\u003e2020b\u003c/span\u003e; Yu et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e; Prasad et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). Some previous studies have also indicated that the structure of the C-S-H gel enhances the mechanical characteristics of concrete (Yu et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e; Prasad et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e; Punurai et al. 2018). Moreover, as compared to a fiber-free case, the presence of additional C-S-H bonds enhances the compressive strength. However, at higher ratios of fiber content, the compressive strength gain may be hindered by the production of larger voids (Bostanci \u003cspan class=\"CitationRef\"\u003e2020b\u003c/span\u003e). The SEM images clearly showed a higher amount of C-S-H bonds and the highest compressive strength in the samples cured with both H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO, particularly in the absence of fibers.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe influence of KP and CC fiber inclusion on the mechanical, thermal insulation, pore structure and microstructure morphology of concrete samples under water, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing conditions is investigated experimentally in this work.\u003c/p\u003e \u003cp\u003eIt is possible to infer the following conclusion:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eThe thermal conductivity coefficient of concrete at 28 days of curing age for all curing groups revealed a pattern that the larger the amount of both KP and CC fiber, the lower the thermal conductivity coefficient.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eSince the fiber-related change in pore structure is the cause of the increase in thermal insulation values, the increased void formation caused by the insulation improvement also resulted in the expected limited declines in compressive strength values in proportion to increasing fiber content.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eA remarkable insulation gain of up to 17.80% could be detected even with the utilization of a small amount of KP fiber at a content of 0.5% in the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing group.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eBased on the detected pore modification effect in the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing group, a maximum of 24.31% enhancement in thermal insulation was achieved with a 10.6% strength loss in the case of 1.5% CC fiber inclusion. Meanwhile, a maximum of 22.26% conductivity reduction with a 12.99% strength decrease was detected in the same curing group and the same fiber amount for the KP fiber inclusion case.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eIn the NaClO curing group, a maximum of 23.55% enhancement in thermal insulation was achieved with a 10.97% strength loss in the case of 1.5% CC fiber inclusion. Similarly, a maximum of 21.01% insulation enhancement with an 11.73% strength reduction was detected in the same curing group and the same fiber amount for the KP fiber inclusion case.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eKP fiber inclusion leads to a significant modification in gel pores and medium capillary pores for both H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing cases. Hence, strong linear correlations were found, with R\u003csup\u003e2\u003c/sup\u003e values of 0.92 and 0.93 for the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing cases, respectively, between the thermal insulation and pore contents in the size range of 100\u0026ndash;1000 nm and 3\u0026ndash;10 nm.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eWhile the addition of KP fibers into the cementitious matrix leads to a remarkable pore modification effect by the proper amount of critical pore contents with the increasing amount of fiber, CC fiber incorporation did not provide a similar effect. At this point, it can be said that regardless of subjected curing conditions, CC fiber leads to a modified pore structure where the proper strength-insulation mechanism from the point of thermal insulation purpose cannot be predicted by only gauged contents or pore diameters.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThis experimental investigation utilized kapok and coconut fiber, which are considered significant sources of raw materials in recent years. The use of these natural fibers is important in terms of sustainability today. The study specifically examined the impact of adding a small amount of KP and CC fibers to concrete samples, which helped to gain a comprehensive understanding of the strength-insulation mechanism in concrete mixtures for thermal insulation purposes. In order to promote sustainable development in the building sector, incorporating a small amount of these natural fibers into concrete mixtures appears to be a useful design strategy. However, when it comes to CC fiber loading, the pore size determined for the changed pore structure resulting from CC incorporation was insufficient to fully elucidate the insulating strength mechanism in CC-incorporated samples. Therefore, further pore structure analysis revealing pore shape, connectivity, and unaccessible pores above the concept of MIP is required to reveal the strength-thermal insulation mechanism of porous concrete matrix containing CC fiber. To the best of our knowledge, within the limits of pore size distribution analysis, this is the first attempt to systematically investigate the strength-thermal insulation mechanism of the KP fiber inclusion case in cement-based mixtures.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contribution\u003c/strong\u003e All authors contributed to the study\u0026rsquo;s conception and design. Material preparation, data collection and analysis were performed by Gulsah Susurluk, Hakan Sarıkaya and Levent Bostancı. The first draft of the manuscript was written by Gulsah Susurluk and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003eNo funding was obtained for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval and consent for\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003epublication\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e The authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAlthoey F, Ansari WS, Sufian M, Deifalla AF 2023) Advancements in low-carbon concrete as a construction material for the sustainable built environment. 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Cellulose. 28:5269\u0026ndash;5292.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Kapok fiber, Coconut fiber, Pore structure, Thermal insulation, Compressive Strength, Sustainability","lastPublishedDoi":"10.21203/rs.3.rs-4099400/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4099400/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eNowadays, when regenerable alternative green sources are attracting more caution under sustainability targets, kapok and coconut fibers, known as natural fibers, have come to the fore as a very significant raw material source. In this experimental study, compressive strength, thermal insulation and pore structure characteristics of kapok fiber (KP) and coconut fiber (CC)-incorporated concrete samples under different curing conditions were analyzed. For that purpose, randomly distributed fiber-incorporated concrete mixtures containing 0%, 0.5%, 1% and 1.5% KP and CC fiber by the weight of cement were prepared and under H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing conditions, the effects of KP and CC fiber inclusion on properties mentioned above of fiber-incorporated concrete samples were researched in detail. Experimental results depict that a maximum thermal conductivity coefficient decrease of 24.31% was detected at a content ratio of 1.5% by the reason of the pore modification effect of used natural fibers in the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e curing group. Because of the remarkable pore modification effect of KP fiber incorporation into the cement matrix compared to the CC fiber inclusion cases, strong linear correlations revealing the insulation-strength mechanism could be detected for both H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and NaClO curing cases. This work intends to promote sustainable development in the building industry by integrating natural fibers into concrete mixtures as an innovative design approach.\u003c/p\u003e","manuscriptTitle":"Utilization of Natural Kapok and Coconut Fiber in Thermally Insulated Sustainable Concrete Design","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-19 18:34:44","doi":"10.21203/rs.3.rs-4099400/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2024-06-21T19:53:34+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-04-11T10:04:56+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-04-11T08:58:34+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2024-04-03T14:22:21+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-03-20T05:18:33+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2024-03-18T06:16:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"4451c526-53f1-42b8-9f5e-f25f57852ed0","owner":[],"postedDate":"April 19th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-10-21T16:00:22+00:00","versionOfRecord":{"articleIdentity":"rs-4099400","link":"https://doi.org/10.1007/s11356-024-35324-0","journal":{"identity":"environmental-science-and-pollution-research","isVorOnly":false,"title":"Environmental Science and Pollution Research"},"publishedOn":"2024-10-18 15:57:07","publishedOnDateReadable":"October 18th, 2024"},"versionCreatedAt":"2024-04-19 18:34:44","video":"","vorDoi":"10.1007/s11356-024-35324-0","vorDoiUrl":"https://doi.org/10.1007/s11356-024-35324-0","workflowStages":[]},"version":"v1","identity":"rs-4099400","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4099400","identity":"rs-4099400","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}