Performance Evaluation of M40 Grade Concrete With GGBS, Fly Ash, and Carbon Nanotube Admixtures: A Comparative Study

Performance Evaluation of M40 Grade Concrete With GGBS, Fly Ash, and Carbon Nanotube Admixtures: A Comparative Study | 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 Article Performance Evaluation of M40 Grade Concrete With GGBS, Fly Ash, and Carbon Nanotube Admixtures: A Comparative Study Girish Chandra Gandhi, Payal Mehta, Ankit Sodha This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7123791/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Concrete, the most commonly used construction materials, encounters issues because of its substantial cement content, leading to environmental harm, alongside limitations in strength and durability. This study examines the mechanical and durability properties of M40 grade concrete modified with Ground Granulated Blast Furnace Slag (GGBS), Fly Ash and Carbon Nanotubes (CNTs). Four types of mixes such as M40 (control), M40 incorporating 40% GGBS, M40 containing 30% Fly Ash and M40 with CNTs (0.01%-0.15%) distributed using supersonication in xylene were examined. The mechanical properties such as compressive, split tensile, and flexural strength were evaluated at 3, 7, and 28 days, in addition to durability tests conducted through Rapid Chloride Penetration and Water Permeability tests. The findings indicated that CNTs notably enhanced performance, especially at concentrations ranging from 0.03–0.05%; especially, the compressive strength increases by 56%, tensile strength increases by around 20% and flexural strength enhanced by around 39% respectively as achieved for 0.03% CNTs. Furthermore, the durability of the CNTs modified concrete has also improved, achieving up to a 100% decrease in water permeability and a 34.56% reduction in chloride penetration. The study concluded that the GGBS- modified concrete outperformed Fly Ash- modified concrete, while CNTs- modified concrete provided the most significant improvements in mechanical and durability properties, showcasing their potential in sustainable concrete. Physical sciences/Engineering Physical sciences/Materials science Ground Granulated Blast Furnace Slag (GGBS) Fly Ash (FA) Carbon Nanotubes (CNTs) Mechanical properties Durability properties 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 Figure 14 1. Introduction The construction sector plays a vital role in modern society and is among the top forty industries projected to be significantly influenced by nanotechnology advancements. Concrete and similar materials are fundamental to this sector (Siddique & Mehta, 2014 ; Carrico et al. 2018 ). Today, concrete remains the most commonly used material in construction worldwide (Naik, 2008 ). It is typically composed of aggregates, water and a binder such as cement or other cementitious substances. The production of cement alone contributes about 8% of the world’s carbon dioxide emissions (Olatoyan et al. 2023 ). To mitigate the environmental impacts associated with concrete production, fly ash has been widely adopted as a supplementary mineral additive. Reducing the cement industry’s carbon footprint and promoting the use of low-carbon technologies is now essential to align with the sustainable development frameworks presented by the International Energy Agency. The incorporation of fly ash as a mineral additive has been widely used to reduce the environmental footprint of conventional concrete production. Bendapudi & Saha ( 2011 ) demonstrated that fly ash can improve concrete’s strength and durability by modifying its pore structure through its pozzolanic activity and particle packing ability. However, recent reductions in coal-fired power generation, combined with stricter environmental regulations on waste disposal, have led to a decline in fly ash availability (Yadav et al. 2022 ). This shortage has highlighted the need for alternative materials that can perform similarly in concrete mixtures without compromising quality. One such alternative being explored is biomass ash, which offers both economic and environmental advantages, including reduced cement usage, lower carbon emissions during production, and effective waste management (Juenger & Siddique, 2015 ). The performance of fly ash in concrete, particularly in terms of strength development, is closely tied to its chemical makeup. Ogawa et al. ( 2010 ) conducted studies to assess the impact of the chemical composition of fly ash on the compressive strength of fly ash-based cement. Furthermore, it was reported that the global production of GGBS reaches approximately 530 million tonnes, with only 65% utilized by the construction industry (Aydın & Baradan, 2014 ). GGBS is a byproduct obtained during the iron production process in the blast furnace. It primarily comprises silicate and aluminosilicate of molten calcium that needed to be extracted regularly from the blast furnace. GGBS contains a substantial amount of amorphous calcium, silica, and alumina, making it an excellent binder for the production of cement concrete. GGBS is a widely used alternative to cement in numerous civil engineering projects, such as the production of concrete. GGBS is a steel production byproduct widely utilized as a cementitious material as it enhances strength and decreases penetrability by increasing the boundary with the aggregate. In addition to offering financial and environmental benefits in power and supply reductions, using GGBS as a binding component in concrete production can lead to considerable cost reductions (Wang & Lee, 2010 ). For more than a century, GGBS served as the main supplementary cement material utilized in the construction industry. GGBS material may possess cementitious and pozzolanic properties. Numerous studies have been conducted regarding the effect of GGBS on the performance of the concrete and mortars (Abbass et al. 2021 ; Sumitha & Abraham, 2016 ). The replacement of OPC reduces the emission of toxic gases and minimizes the consumption of superfluous electricity. In addition to its cost-effectiveness and being ecofriendly, its strength and durability characteristics are equivalent to those of cement. Since 1991, carbon nanotubes (CNTs) have been incorporated into research across various industries including electronics, automotive, and aerospace due to their nanoscale characteristics. These nanotubes possess exceptional mechanical, thermal, and electrical attributes, such as an elastic modulus of 1 TPa, tensile strength reaching 63 GPa, thermal conductivity around 6600 W/m·K, low electrical resistivity (approximately 10⁻⁴ Ω·cm), and the ability to carry electrical currents up to 10⁶ A/cm² (Singh et al. 2017 ). CNTs are typically classified into two types: single-walled and multi-walled varieties (Siddique & Mehta, 2014 ). A unique feature of these carbon structures is their hollow cylindrical form, similar to fullerenes, with diameters ranging from one to several dozen nanometers. Carbon atoms may also be arranged into nanosheet formations, which resemble thin membranes only a few nanometers thick. Carbon nanotubes (CNTs) have emerged as widely used reinforcement materials in the development of advanced high-performance nanocomposites due to their outstanding mechanical characteristics (Hassan et al. 2018 ). In comparison to traditional fibers, CNTs present several distinct advantages as a reinforcement agent in cementitious composites, primarily because of their superior strength and exceptional physical properties (Badawy et al. 2019 ; Hassan et al. 2019 ). Their significantly higher tensile strength and rigidity provide a substantial improvement in the overall mechanical behavior of cement-based materials. The high aspect ratio of CNTs plays a critical role in controlling crack propagation by effectively restricting the extension of nano-cracks (Belytschko et al. 2022). Moreover, CNTs possess excellent flexibility, and their tubular structure enables them to curve and bridge micro- and nano-cracks within the cement matrix. This bridging mechanism contributes notably to enhancing the structural strength of cement composites (Tastani et al. 2016 ). Concrete itself is a cementitious material characterized by a complex calcium-silicate-hydrate (C-S-H) gel network. CNTs exhibit strong interfacial interaction with C-S-H, attributed to their nanoscale features and the abundance of atoms available on the nanotube surface, which facilitates robust bonding at the nano-level (Elkady & Hassan, 2018 ). Understanding, at the nano scale, the performance of the cement matrix and its interaction with other components can be a powerful step in the development of superior concrete with enhanced properties and a more effectively controlled deterioration process. For optimal concrete properties, it is essential that the material offers excellent compaction and resists segregation. Existing studies generally focuses on effect of various additives such as fly ash, ground granulated blast-furnace slag, or limestone on the mechanical performance of the concrete. Recent developments in nanotechnology have led to the production of cost-effective, high-performance cement materials that are increasingly used in civil engineering applications (Eftekhari & Mohammadi, 2016 ). Konsta-Gdoutos et al. ( 2010 ) examined the effect of length of CNT on the mechanical properties of composites by utilizing CNT with short (10-30nm) and long (10–100nm) lengths. They found that the reinforcement level of composites containing 0.025–0.048wt% of long CNT was comparable to that of composites with 0.08wt% of short CNT. Kim et al. ( 2014 ) examined the impact of adding pozzolanic materials with several hundred nanometers on bond strength was examined. Silica fume (10-500nm) served as a dispersing agent for CNT in cement-based composites, penetrating into CNT clusters and subsequently creating a hydration field, thus functioning as a bond between CNT and hydrates. In a study by Morsy et al. ( 2011 ), nano metakaolin (NMK) was incorporated into cementitious composites containing CNT, proving effective in disrupting the attractive forces between CNT particles, which improved the dispersion of CNT. This effect is similar with addition of silica fume, where pozzolanic materials with particle sizes at least 1000 times smaller than cement particles permeate CNT agglomerates. Although conventional concrete mix dependable, substantially increase carbon emissions because of their high cement composition and frequently underperform in harsh environmental circumstances. The rising need for eco-friendly and high-performance materials requires the use of alternative binders and sophisticated additives. While supplementary cementitious materials such as Ground Granulated Blast Furnace Slag (GGBS) and Fly Ash have been thoroughly examined for improving sustainability, their influence on early strength development and long-term durability remains variable. Moreover, the promise of nanomaterials particularly Carbon Nanotubes (CNTs) to enhance microstructure and mechanical properties of the concrete remains largely unexamined and not completely comprehended in practical applications. It is essential to systematically evaluate how the addition of GGBS, Fly Ash, and CNTs, both separately and together, influences the strength and durability properties of concrete. Hence, this study attempts to examine the properties of CNT modified concrete and compared with the properties of GGBS-modified concrete as well as properties of fly ash-modified concrete to validate its potential in concrete applications. 2. Materials and Methodology 2.1 Materials The materials utilized for the concrete sample included Ordinary Portland Cement (OPC) as the binder, River sand as a fine aggregate, coarse aggregate, Potable water, Fly ash, GGBS, CNT, and a superplasticizer (SikaPlast-514 X ) as depicted in Fig. 1 . Grade 53 Ordinary Portland Cement (OPC) conforming to IS 12269 − 1987 was utilized. The chemical composition of cement like silicon dioxide, iron oxide, aluminum oxide, calcium oxide, magnesium oxide, sodium oxide (Na 2 O) and potassium oxide (K 2 O) are presented in Table 1 . The properties of the cement were examined and shown in Table 2 . River Sand conforming to zone-II as per the guidelines of IS: 383 was utilized as Fine Aggregate (FA) in the concrete. The properties of the M-sand were displayed in Table 3 . The well graded angular granite stone with a maximum size of 20mm, meeting the standards of IS: 383–1970, was utilized. The properties of the coarse aggregate were shown in Table 4 . A high-performance water-reducing additive utilized as an admixture in concrete. To ensure the workability of concrete mixes with a low water to binder ratio, a superplasticizer derived from polycarboxylate ether was employed, meeting the standards of ASTM C 494 − 13. The properties of the superplasticizer were shown in Table 5 . This study used a portable tap water that was free from particles like oils, alkalies, acids, salt, sugar and organic materials. The water had a pH value of 7.0 \(\:\underset{\_}{+}\) 1, meeting the IS: 456–2000 standards, for making the concrete. The fly ash obtained from the Ennore thermal power plant was used as a supplementary binder in the concrete mix. As per the ASTMC-618 specification, the fly ash is classified as Class-F. The ignition loss was recorded at 1.9%, the specific gravity was found to be 2.2, and the moisture content was 0.73. The chemical composition of the fly ash is detailed in Table 6 , aligning with the IS: 3812 − 2003 standards. In this research, 30% fly ash was replaced for cement. The Ground granulated blast furnace slag was sourced from JSW Steel Limited in Jindal, Ballari, while the sugar cane bagasse ash was obtained from Koppa Sugar Industry, located in Maddur Taluk, Mandya District, Karnataka. The specific gravity of GGBS was assessed according to IS 4031 − 1988 and was found to be 2.93. In this study, GGBS was incorporated at a replacement ratio of 40% for cement. Multi-walled carbon nanotubes (MWCNTs) were suspended in xylene through supersonication at concentrations of 0.01%, 0.03%, 0.05%, 0.08%, 0.10%, 0.12%, and 0.15% utilized in this study. Table 1 Chemical composition of cement Component Cement (%) Silicon dioxide (SiO 2 ) 22.02 Iron Oxide (Fe 2 O 3 ) 5.12 Aluminium oxide (Al 2 O 3 ) 5.59 Calcium Oxide (CaO) 60.84 Magnesium Oxide (MgO) 1.22 Na 2 O 0.29 K 2 O 0.67 Table 2 Properties of the cement S. No Properties Values Requirements as per IS:12269 − 1987 1 Specific Gravity 3.15 3.15 2 Normal Consistency 31% 25%-35% 3 Initial setting time 40 minutes not less than 30 min 4 Final setting time 345 minutes not more than 600 min 5 Fineness 330 m 2 /kg not be less than 225 m²/kg 6 Soundness 2.50mm not exceed 10 mm Table 3 Properties of the River sand S. No Properties Values IS Standards 1 Dry compacted bulk density (kg/m 3 ) 1575 IS: 2386 (Part 3) 2 Loose compacted bulk density (kg/m 3 ) 1432 IS: 2386 (Part 3) 3 Specific gravity 2.54 IS: 2386 (Part 3) 4 Fineness modulus 2.75 IS: 2386 (Part 1) 5 Moisture content (%) 3 IS: 2386 (Part 3) Table 4 Properties of Coarse aggregate S. No Properties Values IS Standard 1 Dry compacted bulk density (kg/m 3 ) 1680 IS: 2386 (Part 3) 2 Loose compacted bulk density (kg/m 3 ) 1570 IS: 2386 (Part 3) 3 Specific gravity 2.69 IS: 2386 (Part 3) 4 Fineness modulus 6.71 IS: 2386 (Part 1) 5 Water absorption (%) 1.91% IS: 2386 (Part 3) 6 Shape Angular - 7 Impact value (%) 31 IS: 2386 (Part 4) 8 Crushing value (%) 16.88 IS: 2386 (Part 4) 9 Abrasion value (%) 23.4 IS: 2386 (Part 4) Table 5 Properties of Super plasticizer Properties Value Specific gravity 1.82 Chloride Nil pH 7.1 Air entertainment < 2% Solid content 25% Table 6 Chemical composition of the Fly Ash Composition Quantity (%) Al 2 O 3 34.6 SiO 2 59.3 CaO 1.02 MgO 0.38 Fe 2 O 3 5.87 Na 2 O 1.28 SO 3 0.1 K 2 O 0.01 Cl − 0.49 2.2 Mix proportion According to IS: 10262, the concrete for the M40 grade was designed and proportioned to achieve a target compressive strength of 48.25 MPa after 28 days. Subsequently, the concrete was modified with 40% and 30% replacement of cement using GGBS and fly ash. Additionally, the concrete was modified by incorporating CNTs dispersed in xylene through supersonication at concentrations of 0.01%, 0.03%, 0.05%, 0.08%, 0.10%, 0.12%, and 0.15% as a replacement for cement. The various mix proportions utilized in this study are shown in Table 7 and Table 8 . Table 7 Mix proportion for M40, M40-GGBS, M40-fly ash concrete Material M40 M40-GGBS M40-fly ash M1 M2 M3 Quantity (kg/m³) Cement (OPC 53) 430 258 301 GGBS - 172 Fly ash - - 129 Water 162 162 162 Fine Aggregate 728 728 728 Coarse Aggregate 1189 1189 1189 (W/C) 0.40 0.40 0.40 Superplasticizer (%) 4.3 4.3 4.3 Table 8 Mix proportion for M40-CNT concrete Mix ID CNT Dosage Cement (kg/m³) Water (kg/m³) Fine Aggregate (kg/m³) Coarse Aggregate (kg/m³) Super plasticizer (%) CNT (kg/m³) M4-1 0.01% CNT 430 162 728 1189 4.3 0.043 M4-2 0.03% CNT 430 162 728 1189 4.3 0.129 M4-3 0.05% CNT 430 162 728 1189 4.3 0.215 M4-4 0.08% CNT 430 162 728 1189 4.3 0.344 M4-5 0.10% CNT 430 162 728 1189 4.3 0.43 M4-6 0.12% CNT 430 162 728 1189 4.3 0.516 M4-7 0.15% CNT 430 162 728 1189 4.3 0.645 2.3 Preparation of test specimen A freshly prepared concrete mixture is poured into cube, cylinder, and prism molds as shown in Fig. 2– 4 . The specimens were cast according to IS: 516–2021 and IS: 516–2021 for making specimen for various tests using steel molds, compacted in three even layers with a table vibrator to provide external vibration in accordance with IS: 2514 for ensuring sufficient compaction of the concrete. After casting, the samples are kept at room temperature (~ 27°C) for moist curing, prior to testing. The samples were subjected to water curing until testing at 3, 7 and 28 days. 2.4 Experimentations The various tests were designed and conducted adopting American Society for Testing and Materials (ASTM), Bureau of Indian Standards (BIS) and recommendations from the ACI Committee. 2.4.1 Compression testing A cube specimen of dimensions 150 x 150 x 150mm was cast and tested at 3, 7 and 28 days of curing to assess the compressive strength of M40, M40-GGBS, M40-fly ash, and M40-CNT concrete. The examination was conducted following the standards IS: 516–2021 and ACI 544.2R, using a Universal Testing Machine (UTM) capable of 1000kN and with a least count of 1kN, as shown in Fig. 5 . The three samples are tested to find the average compressive strength of each concrete mix. 2.4.2 Split Tensile Testing A cylindrical sample with a height of 200m and a diameter of 100mm was cast and tested at 3, 7 and 28 days of curing to measure the split tensile strength of M40, M40-GGBS, M40-fly ash and M40-CNT concrete. The test was carried out on a cylindrical sample by placing it horizontally between the loading surfaces of the UTM, and the load was applied until failure in accordance with IS 516: 2021, as illustrated in Fig. 6 . The three samples are tested to calculate the mean split tensile strength for each concrete mix. 2.4.3 Flexural testing A prism sample sized 100 mm x 100 mm x 500 mm was cast and tested at 7 and 28 days of curing to assess the flexural strength of M40, M40-GGBS, M40-fly ash, and M40-CNT concrete. The test was carried out following the guidelines of ASTM C78/C78M-21 under four-point loading on a simply supported length of 400mm utilizing a servo-controlled UTM with a capacity of 1000 kN, as shown in Fig. 7 . The three samples are tested to find the average flexural strength for each concrete mixture. 2.4.4 Water Penetration Test The water penetration of a concrete sample was typically conducted in accordance with standards such as EN 12390-8 or DIN 1048. This test assesses the depth to which water penetrates a concrete specimen under pressure, which indicates the concrete’s resistance to water ingress and overall durability. The test begins with the preparation of concrete specimens, usually cubes or cylinders measuring 150 mm × 150 mm × 150 mm. After casting, the specimens are cured in water for 28 days at a controlled temperature of 20°C ± 2°C. Once cured, the surface moisture is allowed to dry naturally without oven-drying, as this can affect the test outcome. The dried specimen is then mounted in a water permeability cell so that one face is exposed to pressurized water, while the remaining faces are sealed using rubber gaskets to prevent edge leakage. Water pressure, typically 5 bar (0.5 MPa), is applied continuously for 72 hours using a pressure pump connected to a water reservoir. During this period, it is essential to maintain constant pressure and check that any water leakage occurs only through the concrete specimen and not due to improper sealing. After 72 hours of pressurized exposure, the sample is removed from the apparatus and split vertically through its center using a compressive testing machine or splitting device. The internal surface of the specimen reveals a darkened zone indicating the depth of water penetration. This depth is measured at three points using a ruler or vernier calliper, and the average of these measurements is recorded in millimetres. 2.4.5 Rapid Chloride Penetration test (RCPT) The Rapid Chloride Penetration test (RCPT) was utilized to assess the resistance to chloride ion ingress of concrete modified with fly ash, GGBS and CNT as per ASTM C1202 standards as presented in Table 9 . The concrete test specimen utilized for this test measured 50 mm in thickness and had a diameter of 100 mm. The test sample was set for 28 days. The concrete specimens were undergone vacuum saturation after 28 days of curing. Following the saturation of the samples, a non-conductive layer was added to the test samples. Next, the sample was positioned between the two cells of the RCPT test device as illustrated in Fig. 8 , where one cell is filled with sodium chloride (NaCl) solution and the other cell is filled with sodium hydroxide (NaOH) solution. A direct current (DC) of 60 volts was utilized across the two cells for a duration of 6 hours. Table 9 RCPT Ratings as per ASTM C1202 Charge Passed (Coulombs) Chloride Ion Penetrability > 4000 High 2000–4000 Moderate 1000–2000 Low 100–1000 Very Low < 100 Negligible 3. Results and Discussions 3.1 Compressive strength of concrete The compressive strength results of concrete mixes that included GGBS, Fly Ash and carbon nanotubes (CNTs) tested after 3, 7 and 28 days was illustrated in Fig. 9 . At 3 days, it was observed that M1 (control mix) possesses a compressive strength of 37.5 N/mm², M2 (GGBS concrete) possesses a 32 N/mm² and M3 (Fly Ash concrete) possesses a 27 N/mm². On the other hand, CNT-modified mixes significantly improved compressive strength as compared to fly and GGBS modified concrete. The highest compressive strength was observed for M4-2 (CNT 0.03%) at 40.5 N/mm², which is about a 26.56% and 50% higher than the compressive strength of GGBS and fly ash modified concrete. It seems that the CNTs contribute significantly to early strength development, likely due to their ability to accelerate cement hydration through enhanced nucleation sites and improved particle dispersion (Gao et al. 2023 ; MacLeod et al. 2021 ; Guo et al. 2025 ). In addition, other CNT mixes such as M4-1, M4-3, M4-4 and M4-6 exhibits better strength than GGBS and fly ash-modified concrete at 3 days, which ranges from 21.88–44.44%. It was observed that the fly ash modified concrete exhibits the lesser strength at 3 days due to its slower pozzolanic reaction, which typically gains strength at later ages. At 3 days, it was observed that M1 (control mix) possesses a compressive strength of 48.5 N/mm², M2 (GGBS concrete) possesses a 44.5 N/mm² and M3 (Fly Ash concrete) possesses a 35 N/mm². On the other hand, CNT-modified mixes significantly improved compressive strength as compared to fly and GGBS modified concrete. The M4-1 (CNT 0.01%) possesses a compressive strength of 54.5 N/mm², which is about 22.47% and 55.71% higher than M2 and M3 mixes. The M4-2 (CNT 0.03%) possesses a compressive strength of 52.5 N/mm², which is about 17.97% and 50% higher than M2 and M3 mixes. These results strongly suggest that even small additions of CNTs can significantly boost strength in the early curing stages. However, mixes with higher CNT contents (e.g., M4-5 at 0.10%) started to show reduced effectiveness, indicating that excessive CNTs may lead to agglomeration and poor dispersion, which can negatively impact the mechanical performance of the concrete (Sobolkina et al. 2012 ; Chen et al. 2016 ; Rubel et al. 2019 ; Reis et al. 2024 ). At 28 days, it was observed that M1 (control mix) possesses a compressive strength of 60 N/mm², M2 (GGBS concrete) possesses a 64 N/mm² and M3 (Fly Ash concrete) possesses a 52 N/mm². The M4-2 (CNT 0.03%) mix possess a highest compressive strength of 65.5 N/mm², which is about 2.34% and 25.96% higher than M2 and M3 mixes. Essentially, several other CNTs added mixes such as M4-3 and M4-6 possesses matched or slightly exceeded strength, of M2 mixes, indicating that properly dosed CNTs can maintain long-term strength without compromising performance. On the other hand, M4-5 and M4-7 mixes gave poorer results compared to M2 mix, further confirming that CNT dosage must be optimized to avoid negative effects such as weak matrix due to clustering. On the other hand, GGBS modified concrete mix showed consistent long-term strength due to the continuation of its latent hydraulic reaction, making it a reliable choice for structural applications requiring gradual strength gain. Fly ash-modified concrete mix possesses poor compressive strength across all ages, despite some improvement over time, reflecting its delayed pozzolanic activity. The CNT-modified concrete significantly outperformed both GGBS- modified concrete and Fly Ash- modified concrete in terms of early-age strength. While long-term strength at 28 days was similar to GGBS concrete, the primary advantage of CNTs lies in their ability to enhance early strength development. The findings concluded that compared to Fly Ash, the CNT-modified concrete was superior across all time frames, emphasizing its potential as a high-performance additive when used at optimal dosages (especially around 0.03%). 3.2 Split tensile strength of concrete The split tensile strength results of concrete mixes that included GGBS, Fly Ash and carbon nanotubes (CNTs) tested after 3, 7 and 28 days was illustrated in Fig. 10 . At 3 days, the GGBS-modified concrete mix and fly ash-modified concrete mix such as M2 and M3 possess a split tensile strength of 3.96 N/mm² and 3.63 N/mm². It was observed that the split tensile strength of CNT modified concrete mixes are higher than of GGBS-modified concrete mix and fly ash-modified concrete mixes. The highest split tensile strength of 4.45 N/mm was obtained for the M4-2 mix which is found to be 12.37% and 22.58% higher than the GGBS-modified concrete mix (M2) and fly ash-modified concrete mix (M3). Similarly, mixes like M4-1, M4-3, M4-4, and M4-6 each achieved 4.37 N/mm², resulting in more than 10% improvement over GGBS and over 20% over Fly Ash. Even mixes with higher CNT content, such as M4-5 and M4-7, showed modest gains over GGBS and noticeable improvements over Fly Ash, although the rate of increase reduced slightly, suggesting potential dispersion issues at higher CNT dosages. These findings highlight the capacity of CNT to improve early-age tensile performance by acting as nucleation sites and bridging microcracks, enhancing the internal structure of the concrete. At 7 days, the GGBS-modified concrete mix and fly ash-modified concrete mix such as M2 and M3 possess a split tensile strength of 4.64 N/mm² and 4.14 N/mm². Further, the CNT mixes continued to show better performance, with M4-1 achieving the highest tensile strength of 5.16 N/mm², which is 11.21% and 24.64% higher than GGBS-modified concrete mix (M2) and fly ash-modified concrete mix (M3). M4-2, M4-3, and M4-4 also demonstrated significant improvements, each exceeding GGBS modified concrete by over 8% and Fly Ash by more than 21%. M4-5 (0.10% CNT) was slightly below GGBS modified concrete, indicating that beyond certain CNT content, the benefits may decrease. However, all CNT mixes offer superior tensile performance as compared to fly ash-modified concrete mix (M3), reflecting its limited early strength due to the delayed pozzolanic reaction. At 28 days, GGBS-modified concrete reached a tensile strength of 5.60 N/mm², slightly outperforming the control (M1) and remaining well ahead of fly ash-modified concrete, which reached 5.05 N/mm². The CNT concrete with 0.03% CNT (M4-2) exhibited the highest split tensile strength at 5.66 N/mm², slightly surpassing GGBS by 1.07% and exceeding fly ash-modified concrete by 12.08%. M4-3 and M4-6 also performed marginally better than GGBS-modified concrete, while other mixes like M4-1, M4-4, and M4-7 closely matched or slightly underperformed GGBS-modified concrete. Although the differences at 28 days were modest, CNT mixes still demonstrated significant improvement over fly Ash-modified concrete, which remained the weakest performer. The CNT-modified concretes showed considerable improvements in split tensile strength at all ages compared to both GGBS and Fly Ash concretes. While GGBS concrete exhibited solid long-term performance, CNTs delivered more pronounced benefits at early stages, making them especially valuable for applications requiring rapid strength gain. Fly Ash concrete consistently displayed the lowest strength values, confirming its slower strength development. The optimum CNT dosage was found to be around 0.03%, beyond which efficiency began to decline, likely due to particle agglomeration and poor dispersion. These findings concluded that when used in optimal proportions, CNTs can significantly enhance the tensile properties of concrete, offering a promising solution for high-performance, early-strength applications. 3.3 Flexural strength of concrete The flexural strength results of concrete mixes that included GGBS, Fly Ash and carbon nanotubes (CNTs) tested after 7 and 28 days was illustrated in Fig. 11 . At 7 days, GGBS modified concrete (M2) recorded a flexural strength of 4.25 N/mm², slightly higher than fly ash modified concrete (M3), which had 4.21 N/mm². However, CNT-enhanced concretes showed notable improvements. The highest strength at this age was achieved by the mix containing 0.03% CNT (M4-2), with 5.90 N/mm², representing a 38.82% increase over GGBS and 40.14% over Fly Ash. Other CNT mixes also outperformed GGBS and Fly Ash, with M4-6 (0.12% CNT) showing a 27.53% increase over GGBS, and M4-5 (0.10% CNT) and M4-3 (0.05% CNT) showing increases of 9.65% and 15.29% respectively. These results highlight the significant enhancement in early-age flexural strength due to CNTs, likely attributed to their ability to bridge microcracks, enhance bonding within the cement matrix, and improve the overall load transfer capability of the composite. After 28 days, the pattern of enhanced flexural strength in CNT mixtures persisted. The GGBS-modified concrete attained 4.82 N/mm², slightly exceeding the flexural strength of fly ash modified concrete of 4.78 N/mm². Once more, CNT-modified mixes exceeded both, with M4-2 (0.03% CNT) recording the peak strength of 6.65 N/mm², reflecting a 37.97% rise compared to GGBS modified concrete and a 39.12% increase over fly ash modified concrete mixes. Other mixes like M4-6 (0.12% CNT) and M4-5 (0.10% CNT) achieved 6.49 N/mm² and 6.11 N/mm², demonstrating enhancements of 34.65% and 26.77% compared to GGBS, respectively. Even the least effective CNT blend (M4-7 with 0.15% CNT) showed a 14.52% improvement compared to GGBS. These findings suggest that CNTs play a crucial role in enhancing long-term flexural strength, particularly when utilized within an ideal range. The increase in strength is probably a result of the significant tensile capabilities of CNTs and their efficient interaction with the cement matrix, which improves crack resistance and overall structural integrity. 3.4 Chloride penetration resistance of concrete Table 10 presents the Rapid Chloride Penetration Test (RCPT) results for concrete mixes with varying percentages of carbon nanotubes (CNTs), which provide important insights into the influence of CNTs on chloride ion permeability and overall durability. As per ASTM C1202 standards, chloride ion penetrability is classified based on the charge passed in Coulombs: greater than 4000 is High, 2000–4000 is Moderate, 1000–2000 is Low, 100–1000 is Very Low, and less than 100 is Negligible. Based on this standard, the CNT-modified concrete mixes are assessed and compared with the control (M1) for durability performance. The control mix M1 (0% CNT) recorded a charge passed of 1360 Coulombs, classifying it under “Low” chloride ion permeability, which corresponds to high durability. The incorporation of CNTs at low dosages further improved resistance to chloride ion ingress. For example, M4-1 (0.01% CNT) showed a reduced charge passed of 1297 Coulombs, while M4-2 (0.03% CNT) achieved 1192 Coulombs both still in the “Low” category but indicating improved performance over the control, with respective reductions of 4.63% and 12.35% in chloride permeability. These reductions reflect the densification of the cement matrix and crack-bridging ability of CNTs, which reduce the interconnected porosity. A significant improvement was observed in M4-3 (0.05% CNT), which had a charge passed of 890 Coulombs, falling into the “Very Low” chloride ion permeability category. This result marks a 34.56% decrease in permeability compared to the control and represents a shift to “Very High” durability, indicating that 0.05% CNT is an optimal dosage for enhancing resistance against chloride ion penetration. This improvement can be attributed to the effective dispersion and network formation of CNTs at this dosage, which significantly obstructs the movement of chloride ions by refining the pore structure and promoting secondary hydration. However, as the CNT content increased further, the performance trend fluctuated. For instance, M4-4 (0.08% CNT) exhibited a higher charge passed (1477 Coulombs) than the control, indicating a deterioration in permeability performance. This may be due to agglomeration of CNTs at higher concentrations, which can disrupt matrix homogeneity and increase localized porosity. Similarly, M4-6 (0.12% CNT) showed a charge of 1352 Coulombs, very close to the control, indicating no significant improvement, while M4-5 (0.10% CNT) and M4-7 (0.15% CNT) returned better results with 1154 Coulombs and 1143 Coulombs, respectively, both within the “Low” category but showing improved durability relative to M1. In summary, all CNT-modified concretes maintained at least “Low” chloride ion permeability according to ASTM C1202, ensuring high durability. The most substantial enhancement was observed at 0.05% CNT, where the mix achieved “Very Low” chloride ion permeability, representing the best performance in terms of durability. This suggests that optimal CNT dosage lies around 0.05%, beyond which the benefits plateau or decline due to dispersion challenges. Thus, CNTs, when used effectively, can significantly improve the durability of concrete by minimizing chloride ingress and enhancing microstructural integrity. Table 10 RCPT values of various concrete mixes Mix ID Coulomb Chloride ion Penetration level M1 1360 Low M4-1 1297 Low M4-2 1192 Low M4-3 890 Very Low M4-4 1477 Low M4-5 1154 Low M4-6 1352 Low 3.4 Water penetration resistance of concrete Table 11 presents the outcomes of water permeability test, which offer insights into the ability of concrete to withstand water infiltration, which is essential for durability, particularly in structures subjected to aggressive conditions. The control mix (M1) and mixes containing diverse percentages of carbon nanotubes (CNTs) demonstrate a distinct trend of performance enhancement attributed to the inclusion of CNTs. The control mix (M1) showed an average water penetration depth of 6 mm. This implies that the matrix contained localized weak spots or interconnected pores that allowed water ingress. In comparison, all CNT modified mixes demonstrated considerably enhanced water resistance, with most exhibiting zero or nearly zero permeability. The M4-1 (0.01% CNT) blend showed no water infiltration, yielding an average of 0 mm, clearly indicating better impermeability than the control. This pattern persisted in M4-5 (0.10%), M4-6 (0.12%), and M4-7 (0.15%), all of which similarly showed zero average penetration, demonstrating total resistance to water under the testing conditions. These findings indicate the beneficial effect of CNTs in decreasing capillary pores and filling microcracks, thus improving the impermeability of the concrete matrix. The M4-2 (0.03%) and M4-3 (0.05%) mixtures exhibited slight penetration, averaging 1 mm. The average penetration of M4-4 (0.08%) reached 2 mm which was still noticeably higher than that of the control. An increase in permeability observed in M4-4 may result from the CNTs were dispersed at that amount which led to regional micro voids or a non-uniform structure in the membrane. Adding CNTs reduced the water permeability by a lot, with average water penetration decreasing from 6 mm with the control mix to 0–2 mm in the modified concretes. This leads to a better impermeability range of 83–100%. In mixes with 0.01%, 0.10%, 0.12% and 0.15% CNTs, we observed full water resistance. The advantages from these CNTs lay in their ability to adjust the pore structure, fill nano-scale voids, and bridge microcracks, helping to make concrete denser and more impermeable. In conclusion, the water permeability test results that incorporating CNTs into concrete greatly improves its impermeability and the best effect can be seen with both lower and mid-range dosages of CNTs. This improvement in water tightness directly translates to increased resistance to deterioration mechanisms like corrosion, freeze-thaw cycles and sulfate attack, thereby greatly improving the long-term durability of concrete structures. Table 11 Water penetration rate of concrete Mix ID Average Water penetration (mm) M1 6 M4-1 0 M4-2 1 M4-3 1 M4-4 2 M4-5 0 M4-6 0 M4-7 0 4. Conclusions This study comprehensively evaluated the effects of incorporating Carbon Nanotubes (CNTs) into concrete, comparing them against GGBS and Fly Ash-modified concrete mixes. CNT-modified concretes showed significant improvements in all mechanical and durability measurements. Compressive strength increased by as much as 50% at 3 days, 55.71% at 7 days, and 25.96% at 28 days in comparison to Fly Ash concrete. Tensile strength improvements reached 22.58% (3 days), 24.64% (7 days), and 12.08% (28 days) compared to Fly Ash concrete, with CNT mixes such as M4-2 (0.03%) exceeding the performance of all alternatives. Flexural strength demonstrated a 40.14% increase at 7 days and a 39.12% rise at 28 days, further validating the reinforcing properties of CNTs. Durability measurements showed comparable patterns. Chloride permeability reduced by 34.56%, moving from the “Low” to “Very Low” category according to ASTM C1202. Water permeability decreased by 83%-100%, with M4-1, M4-5, M4-6, and M4-7 reaching no penetration. However, an excessive CNT dosage (e.g., ≥ 0.08%) caused performance declines of up to 8.6% because of particle agglomeration. The findings determined that CNTs greatly improved both short-term and long-term performance, particularly within an optimal dosage range of 0.03% (M4-2 mix), providing a balanced boost in strength (up to 56%), impermeability (up to 100%), thus outperforming conventional additives such as GGBS and Fly Ash. Declarations Author Contribution G.C. Gandhi: Conceptualization, Methodology, Investigation, Data Curation, Formal Analysis, Writing - Original DraftP. Mehta: Supervision, Resources, Validation, Writing - Review & EditingA. Sodha: Visualization, Software, Formal Analysis, Writing - Review & Editing Acknowledgement The authors sincerely express their gratitude to Unique Geo Civil Services Pvt. Ltd., Surat, Gujarat, for their technical support and cooperation throughout the experimental phase of this research. Special thanks are extended to KBM Engineering Research Laboratory, Ahmedabad, and Modi Laboratory, Ahmedabad, for providing essential testing facilities and infrastructure that significantly contributed to the successful execution of this study. The authors also wish to acknowledge Ms. Meena Lochani, Research Scholar, Indus University, Ahmedabad, for her valuable inputs and collaborative support during the data collection and analysis stages. Heartfelt appreciation is extended to Mr. Harshil Parikh, former Design Director, Larsen & Toubro, Dholera, for his insightful discussions and technical suggestions, which helped refine the structural aspects of the research. The authors are also grateful to Ms. Jyotsna Gautam, General Manager and Cluster Head (N & W), Larsen & Toubro, Ahmedabad, and Ms. Juhi Gandhi, Techno Commercial Manager of Adani Green, Ahmedabad for her encouragement and professional guidance, which played a vital role in shaping the practical relevance of the work. Data Availability The datasets used and/or analysed during the current study available from the corresponding author on reasonable request. References Abbass, M., Singh, D. & Singh, G. Properties of hybrid geopolymer concrete prepared using rice husk ash, fly ash and GGBS with coconut fiber. Materials Today: Proceedings , 45 , 4964–4970. (2021). Aydın, S. & Baradan, B. Effect of activator type and content on properties of alkali-activated slag mortars. Compos. Part. B: Eng. 57 , 166–172 (2014). Badawy, A. H., El-Feky, M. S., Hassan, A., El-kady, H., Hafez, A. E. & L. M Flexural behavior of unbounded pre-stressed beams modified with carbon nanotubes under elevated temperature. Civil Eng. J. 5 (4), 856–870 (2019). Belytschko, T., Xiao, S. P., Schatz, G. C. & Ruoff, R. S. Atomistic simulations of nanotube fracture. Phys. Rev. B . 65 (23), 235430 (2002). Bendapudi, S. C. K. & Saha, P. Contribution of fly ash to the properties of mortar and concrete. Int. J. Earth Sci. Eng. 4 (6), 1017–1023 (2011). Carrico, A., Bogas, J. A., Hawreen, A. & Guedes, M. Durability of multi-walled carbon nanotube reinforced concrete. Constr. Build. Mater. 164 , 121–133 (2018). Chen, S. J., Qiu, C. Y., Korayem, A. H., Barati, M. R. & Duan, W. H. Agglomeration process of surfactant-dispersed carbon nanotubes in unstable dispersion: A two-stage agglomeration model and experimental evidence. Powder Technol. 301 , 412–420 (2016). Eftekhari, M. & Mohammadi, S. Multiscale dynamic fracture behavior of the carbon nanotube reinforced concrete under impact loading. Int. J. Impact Eng. 87 , 55–64 (2016). Elkady, H. & Hassan, A. Assessment of high thermal effects on carbon nanotube (cnt)-reinforced concrete. Sci. Rep. 8 (1), 11243 (2018). Gao, Y. et al. Dispersion of carbon nanotubes in aqueous cementitious materials: A review. Nanatechnol. Reviews . 12 (1), 20220560 (2023). Guo, E. et al. Enhancement of Cement-Based Materials: Mechanisms, Impacts, and Applications of Carbon Nanotubes in Microstructural Modification. Buildings 15 (8), 1234 (2025). Hassan, A., Elkady, H. & Shaaban, I. G. Effect of adding carbon nanotubes on corrosion rates and steel-concrete bond. Sci. Rep. 9 (1), 6285 (2019). Hassan, A., Shoeib, A. E. K. & Abd El-Magied, M. Use of carbon nanotubes in the retrofitting of reinforced concrete beams with an opening and the effect of direct fire on their behaviour. GEOMATE J. 14 (44), 149–158 (2018). Juenger, M. C. & Siddique, R. Recent advances in understanding the role of supplementary cementitious materials in concrete. Cem. Concr. 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Evaluation of fly ash as cementitious material for strength. J. Cem. Sci. Concr Technol. 64 , 131–138 (2010). Olatoyan, O. J., Kareem, M. A., Adebanjo, A. U., Olawale, S. O. A. & Alao, K. T. Potential use of biomass ash as a sustainable alternative for fly ash in concrete production: A review. Hybrid. Adv. 4 , 100076 (2023). Reis, E. D. et al. Assessment of physical and mechanical properties of concrete with carbon nanotubes pre-dispersed in cement. J. Building Eng. 89 , 109255 (2024). Rubel, R. I., Ali, M. H., Jafor, M. A. & Alam, M. M. Carbon nanotubes agglomeration in reinforced composites: A review. AIMS Mater. Sci. 6 (5), 756–780 (2019). Siddique, R. & Mehta, A. Effect of carbon nanotubes on properties of cement mortars. Constr. Build. Mater. 50 , 116–129 (2014). Singh, A., Prabhu, T. R., Sanjay, A. R. & Koti, V. An overview of processing and properties of Cu/CNT nano composites. Materials today: proceedings , 4 (2), 3872–3881. (2017). Sobolkina, A. et al. Dispersion of carbon nanotubes and its influence on the mechanical properties of the cement matrix. Cem. Concr. Compos. 34 (10), 1104–1113 (2012). Sumitha, Y. & Abraham, R. Experimental Study on bentonite clay powder with silica fume and GGBS as partial replacement of cement in M40 grade concrete. Int. J. Eng. Res. Technol. 5 , 339–343 (2016). Tastani, S. P., Konsta-Gdoutos, M. S., Pantazopoulou, S. J. & Balopoulos, V. The effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient cementitious composites. Front. Struct. Civil Eng. 10 , 214–223 (2016). Wang, X. Y. & Lee, H. S. Modeling the hydration of concrete incorporating fly ash or slag. Cem. Concr. Res. 40 (7), 984–996 (2010). Yadav, V. K. et al. Status of coal-based thermal power plants, coal fly ash production, utilization in India and their emerging applications. Minerals 12 (12), 1503 (2022). Additional Declarations No competing interests reported. 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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-7123791","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":504738353,"identity":"a6124731-e98c-46d6-8bcf-063325c743b9","order_by":0,"name":"Girish Chandra Gandhi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABBElEQVRIiWNgGAWjYDACCQYDICnHA2IfSKgAkszMDcRoMQZpYTzw4AxICyNxWkBM5oMP20A0AS3m0s2bX1fUGMgYnF/84EDivNpo/naglh8V23BqsZxzrMzyzDEDHskZzwwOJG47njvjMGMDY8+Z2zi1GNzIMTNsYPvDwy9xhgGo5VhuA1ALM2MbIS3/DHjYwFrmHMudT4QW44eNbQY8/Pw9QC0NNbkbCGmxnJFWxtjYB/ILm8GBhGMHcjcCtRzE5xdzieTNHxu+GdgbnD/8+OOPmrrceecPH3zwowKPwxgY2CTALIkEEHkYzD6AUz1EC/MHMIsfrK4On+JRMApGwSgYoQAAiE5isgzVRd0AAAAASUVORK5CYII=","orcid":"","institution":"Indus Institute of Technology and Engineering, Indus University","correspondingAuthor":true,"prefix":"","firstName":"Girish","middleName":"Chandra","lastName":"Gandhi","suffix":""},{"id":504738358,"identity":"345edcd2-e133-4c6b-996a-a5556dc575ab","order_by":1,"name":"Payal Mehta","email":"","orcid":"","institution":"Indus Institute of Technology and Engineering, Indus University","correspondingAuthor":false,"prefix":"","firstName":"Payal","middleName":"","lastName":"Mehta","suffix":""},{"id":504738360,"identity":"e158e1df-e6d4-4a02-a8cf-768b64dc391e","order_by":2,"name":"Ankit Sodha","email":"","orcid":"","institution":"Indus Institute of Technology and Engineering, Indus University","correspondingAuthor":false,"prefix":"","firstName":"Ankit","middleName":"","lastName":"Sodha","suffix":""}],"badges":[],"createdAt":"2025-07-14 18:23:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7123791/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7123791/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":90179626,"identity":"e481a985-6dcb-4733-8471-0771e0e43654","added_by":"auto","created_at":"2025-08-29 13:10:40","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":401542,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMaterials Used\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7123791/v1/e663f90e535a11196889f291.png"},{"id":90179600,"identity":"16d4d9cd-3576-4d76-b00b-1706ab0c2a69","added_by":"auto","created_at":"2025-08-29 13:10:39","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":421236,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMixing \u0026amp; Casting of concrete\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7123791/v1/a5f724ab0afa7db25ff5973f.png"},{"id":90179605,"identity":"909fedaa-dd39-4a49-9ef7-5c3da652dbaa","added_by":"auto","created_at":"2025-08-29 13:10:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":392885,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCube specimen \u0026amp; Cylinder specimens\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7123791/v1/9fc6a958bb92d248398bc48a.png"},{"id":90179589,"identity":"0518b360-2b7c-449c-92e0-f739cd91c1f8","added_by":"auto","created_at":"2025-08-29 13:10:38","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":477252,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePrism specimens\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7123791/v1/d8c594de326a3a82fb520481.png"},{"id":90179588,"identity":"bf960685-7475-4497-a159-c2310595b9d9","added_by":"auto","created_at":"2025-08-29 13:10:38","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":383932,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCuring of concrete specimens\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7123791/v1/add72ff54f75836b04487655.png"},{"id":90179978,"identity":"64b0a4c9-acd5-4bb6-8a63-76c0adfb4899","added_by":"auto","created_at":"2025-08-29 13:18:39","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":521327,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 5. 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Compressive strength of various concrete mixes\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"9a.png","url":"https://assets-eu.researchsquare.com/files/rs-7123791/v1/3f1489cf082f42f7c54f52ee.png"},{"id":90179980,"identity":"8e390c43-f2db-4326-b880-ee1017b1a8ed","added_by":"auto","created_at":"2025-08-29 13:18:39","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":43278,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 10. Split tensile strength of various concrete mixes\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-7123791/v1/1789b3a721f43fc4bb603a4e.png"},{"id":90179603,"identity":"7751e0bc-7f2c-4fcf-8f2f-66c1f80b0fef","added_by":"auto","created_at":"2025-08-29 13:10:39","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":29251,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 11. Flexural strength of various concrete mixes\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-7123791/v1/8665c76d1eff383f3500f5fe.png"},{"id":90179601,"identity":"388d2f4f-e1cb-41e6-b574-1b07163efeb0","added_by":"auto","created_at":"2025-08-29 13:10:39","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":82791,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 12. RCPT values of various concrete mixes\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-7123791/v1/a79185a674a24b4598f27e2f.png"},{"id":90408954,"identity":"b27d3f07-09de-412b-bf1b-c90670205021","added_by":"auto","created_at":"2025-09-02 11:47:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6995713,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7123791/v1/d63b924d-e253-43a0-9bfd-ad002cc7f0ca.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003ePerformance Evaluation of M40 Grade Concrete With GGBS, Fly Ash, and Carbon Nanotube Admixtures: A Comparative Study\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe construction sector plays a vital role in modern society and is among the top forty industries projected to be significantly influenced by nanotechnology advancements. Concrete and similar materials are fundamental to this sector (Siddique \u0026amp; Mehta, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Carrico et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Today, concrete remains the most commonly used material in construction worldwide (Naik, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). It is typically composed of aggregates, water and a binder such as cement or other cementitious substances. The production of cement alone contributes about 8% of the world\u0026rsquo;s carbon dioxide emissions (Olatoyan et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). To mitigate the environmental impacts associated with concrete production, fly ash has been widely adopted as a supplementary mineral additive. Reducing the cement industry\u0026rsquo;s carbon footprint and promoting the use of low-carbon technologies is now essential to align with the sustainable development frameworks presented by the International Energy Agency. The incorporation of fly ash as a mineral additive has been widely used to reduce the environmental footprint of conventional concrete production. Bendapudi \u0026amp; Saha (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) demonstrated that fly ash can improve concrete\u0026rsquo;s strength and durability by modifying its pore structure through its pozzolanic activity and particle packing ability. However, recent reductions in coal-fired power generation, combined with stricter environmental regulations on waste disposal, have led to a decline in fly ash availability (Yadav et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). This shortage has highlighted the need for alternative materials that can perform similarly in concrete mixtures without compromising quality. One such alternative being explored is biomass ash, which offers both economic and environmental advantages, including reduced cement usage, lower carbon emissions during production, and effective waste management (Juenger \u0026amp; Siddique, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The performance of fly ash in concrete, particularly in terms of strength development, is closely tied to its chemical makeup. Ogawa et al. (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) conducted studies to assess the impact of the chemical composition of fly ash on the compressive strength of fly ash-based cement.\u003c/p\u003e\u003cp\u003eFurthermore, it was reported that the global production of GGBS reaches approximately 530\u0026nbsp;million tonnes, with only 65% utilized by the construction industry (Aydın \u0026amp; Baradan, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). GGBS is a byproduct obtained during the iron production process in the blast furnace. It primarily comprises silicate and aluminosilicate of molten calcium that needed to be extracted regularly from the blast furnace. GGBS contains a substantial amount of amorphous calcium, silica, and alumina, making it an excellent binder for the production of cement concrete. GGBS is a widely used alternative to cement in numerous civil engineering projects, such as the production of concrete. GGBS is a steel production byproduct widely utilized as a cementitious material as it enhances strength and decreases penetrability by increasing the boundary with the aggregate. In addition to offering financial and environmental benefits in power and supply reductions, using GGBS as a binding component in concrete production can lead to considerable cost reductions (Wang \u0026amp; Lee, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). For more than a century, GGBS served as the main supplementary cement material utilized in the construction industry. GGBS material may possess cementitious and pozzolanic properties. Numerous studies have been conducted regarding the effect of GGBS on the performance of the concrete and mortars (Abbass et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Sumitha \u0026amp; Abraham, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The replacement of OPC reduces the emission of toxic gases and minimizes the consumption of superfluous electricity. In addition to its cost-effectiveness and being ecofriendly, its strength and durability characteristics are equivalent to those of cement.\u003c/p\u003e\u003cp\u003eSince 1991, carbon nanotubes (CNTs) have been incorporated into research across various industries including electronics, automotive, and aerospace due to their nanoscale characteristics. These nanotubes possess exceptional mechanical, thermal, and electrical attributes, such as an elastic modulus of 1 TPa, tensile strength reaching 63 GPa, thermal conductivity around 6600 W/m\u0026middot;K, low electrical resistivity (approximately 10⁻⁴ Ω\u0026middot;cm), and the ability to carry electrical currents up to 10⁶ A/cm\u0026sup2; (Singh et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). CNTs are typically classified into two types: single-walled and multi-walled varieties (Siddique \u0026amp; Mehta, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). A unique feature of these carbon structures is their hollow cylindrical form, similar to fullerenes, with diameters ranging from one to several dozen nanometers. Carbon atoms may also be arranged into nanosheet formations, which resemble thin membranes only a few nanometers thick. Carbon nanotubes (CNTs) have emerged as widely used reinforcement materials in the development of advanced high-performance nanocomposites due to their outstanding mechanical characteristics (Hassan et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In comparison to traditional fibers, CNTs present several distinct advantages as a reinforcement agent in cementitious composites, primarily because of their superior strength and exceptional physical properties (Badawy et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Hassan et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Their significantly higher tensile strength and rigidity provide a substantial improvement in the overall mechanical behavior of cement-based materials. The high aspect ratio of CNTs plays a critical role in controlling crack propagation by effectively restricting the extension of nano-cracks (Belytschko et al. 2022). Moreover, CNTs possess excellent flexibility, and their tubular structure enables them to curve and bridge micro- and nano-cracks within the cement matrix. This bridging mechanism contributes notably to enhancing the structural strength of cement composites (Tastani et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Concrete itself is a cementitious material characterized by a complex calcium-silicate-hydrate (C-S-H) gel network. CNTs exhibit strong interfacial interaction with C-S-H, attributed to their nanoscale features and the abundance of atoms available on the nanotube surface, which facilitates robust bonding at the nano-level (Elkady \u0026amp; Hassan, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Understanding, at the nano scale, the performance of the cement matrix and its interaction with other components can be a powerful step in the development of superior concrete with enhanced properties and a more effectively controlled deterioration process. For optimal concrete properties, it is essential that the material offers excellent compaction and resists segregation. Existing studies generally focuses on effect of various additives such as fly ash, ground granulated blast-furnace slag, or limestone on the mechanical performance of the concrete. Recent developments in nanotechnology have led to the production of cost-effective, high-performance cement materials that are increasingly used in civil engineering applications (Eftekhari \u0026amp; Mohammadi, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Konsta-Gdoutos et al. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) examined the effect of length of CNT on the mechanical properties of composites by utilizing CNT with short (10-30nm) and long (10\u0026ndash;100nm) lengths. They found that the reinforcement level of composites containing 0.025\u0026ndash;0.048wt% of long CNT was comparable to that of composites with 0.08wt% of short CNT. Kim et al. (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) examined the impact of adding pozzolanic materials with several hundred nanometers on bond strength was examined. Silica fume (10-500nm) served as a dispersing agent for CNT in cement-based composites, penetrating into CNT clusters and subsequently creating a hydration field, thus functioning as a bond between CNT and hydrates. In a study by Morsy et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), nano metakaolin (NMK) was incorporated into cementitious composites containing CNT, proving effective in disrupting the attractive forces between CNT particles, which improved the dispersion of CNT. This effect is similar with addition of silica fume, where pozzolanic materials with particle sizes at least 1000 times smaller than cement particles permeate CNT agglomerates.\u003c/p\u003e\u003cp\u003eAlthough conventional concrete mix dependable, substantially increase carbon emissions because of their high cement composition and frequently underperform in harsh environmental circumstances. The rising need for eco-friendly and high-performance materials requires the use of alternative binders and sophisticated additives. While supplementary cementitious materials such as Ground Granulated Blast Furnace Slag (GGBS) and Fly Ash have been thoroughly examined for improving sustainability, their influence on early strength development and long-term durability remains variable. Moreover, the promise of nanomaterials particularly Carbon Nanotubes (CNTs) to enhance microstructure and mechanical properties of the concrete remains largely unexamined and not completely comprehended in practical applications. It is essential to systematically evaluate how the addition of GGBS, Fly Ash, and CNTs, both separately and together, influences the strength and durability properties of concrete. Hence, this study attempts to examine the properties of CNT modified concrete and compared with the properties of GGBS-modified concrete as well as properties of fly ash-modified concrete to validate its potential in concrete applications.\u003c/p\u003e"},{"header":"2. Materials and Methodology","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Materials\u003c/h2\u003e\u003cp\u003eThe materials utilized for the concrete sample included Ordinary Portland Cement (OPC) as the binder, River sand as a fine aggregate, coarse aggregate, Potable water, Fly ash, GGBS, CNT, and a superplasticizer (SikaPlast-514 X ) as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Grade 53 Ordinary Portland Cement (OPC) conforming to IS 12269\u0026thinsp;\u0026minus;\u0026thinsp;1987 was utilized. The chemical composition of cement like silicon dioxide, iron oxide, aluminum oxide, calcium oxide, magnesium oxide, sodium oxide (Na\u003csub\u003e2\u003c/sub\u003eO) and potassium oxide (K\u003csub\u003e2\u003c/sub\u003eO) are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The properties of the cement were examined and shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. River Sand conforming to zone-II as per the guidelines of IS: 383 was utilized as Fine Aggregate (FA) in the concrete. The properties of the M-sand were displayed in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The well graded angular granite stone with a maximum size of 20mm, meeting the standards of IS: 383\u0026ndash;1970, was utilized. The properties of the coarse aggregate were shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. A high-performance water-reducing additive utilized as an admixture in concrete. To ensure the workability of concrete mixes with a low water to binder ratio, a superplasticizer derived from polycarboxylate ether was employed, meeting the standards of ASTM C 494\u0026thinsp;\u0026minus;\u0026thinsp;13. The properties of the superplasticizer were shown in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. This study used a portable tap water that was free from particles like oils, alkalies, acids, salt, sugar and organic materials. The water had a pH value of 7.0 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\underset{\\_}{+}\\)\u003c/span\u003e\u003c/span\u003e1, meeting the IS: 456\u0026ndash;2000 standards, for making the concrete. The fly ash obtained from the Ennore thermal power plant was used as a supplementary binder in the concrete mix. As per the ASTMC-618 specification, the fly ash is classified as Class-F. The ignition loss was recorded at 1.9%, the specific gravity was found to be 2.2, and the moisture content was 0.73. The chemical composition of the fly ash is detailed in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, aligning with the IS: 3812\u0026thinsp;\u0026minus;\u0026thinsp;2003 standards. In this research, 30% fly ash was replaced for cement. The Ground granulated blast furnace slag was sourced from JSW Steel Limited in Jindal, Ballari, while the sugar cane bagasse ash was obtained from Koppa Sugar Industry, located in Maddur Taluk, Mandya District, Karnataka. The specific gravity of GGBS was assessed according to IS 4031\u0026thinsp;\u0026minus;\u0026thinsp;1988 and was found to be 2.93. In this study, GGBS was incorporated at a replacement ratio of 40% for cement. Multi-walled carbon nanotubes (MWCNTs) were suspended in xylene through supersonication at concentrations of 0.01%, 0.03%, 0.05%, 0.08%, 0.10%, 0.12%, and 0.15% utilized in this study.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eChemical composition of cement\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eComponent\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCement (%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSilicon dioxide (SiO\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e22.02\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIron Oxide (Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAluminium oxide (Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.59\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCalcium Oxide (CaO)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e60.84\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMagnesium Oxide (MgO)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.22\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNa\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.29\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.67\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eProperties of the cement\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eS. No\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eProperties\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eValues\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eRequirements as per IS:12269\u0026thinsp;\u0026minus;\u0026thinsp;1987\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSpecific Gravity\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNormal Consistency\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e25%-35%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eInitial setting time\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e40 minutes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003enot less than 30 min\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFinal setting time\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e345 minutes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003enot more than 600 min\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFineness\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e330 m\u003csup\u003e2\u003c/sup\u003e/kg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003enot be less than 225 m\u0026sup2;/kg\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSoundness\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.50mm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003enot exceed 10 mm\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eProperties of the River sand\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eS. No\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eProperties\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eValues\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS Standards\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDry compacted bulk density (kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1575\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLoose compacted bulk density (kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1432\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSpecific gravity\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFineness modulus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 1)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMoisture content (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eProperties of Coarse aggregate\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eS. No\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eProperties\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eValues\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS Standard\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDry compacted bulk density (kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1680\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLoose compacted bulk density (kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1570\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSpecific gravity\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFineness modulus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 1)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWater absorption (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.91%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eShape\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAngular\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eImpact value (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 4)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCrushing value (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e16.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 4)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAbrasion value (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIS: 2386 (Part 4)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eProperties of Super plasticizer\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProperties\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eValue\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpecific gravity\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.82\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChloride\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNil\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003epH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAir entertainment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;2%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSolid content\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e25%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eChemical composition of the Fly Ash\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eComposition\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eQuantity (%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e34.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e59.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCaO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.02\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMgO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.87\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNa\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.28\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCl\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.49\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Mix proportion\u003c/h2\u003e\u003cp\u003eAccording to IS: 10262, the concrete for the M40 grade was designed and proportioned to achieve a target compressive strength of 48.25 MPa after 28 days. Subsequently, the concrete was modified with 40% and 30% replacement of cement using GGBS and fly ash. Additionally, the concrete was modified by incorporating CNTs dispersed in xylene through supersonication at concentrations of 0.01%, 0.03%, 0.05%, 0.08%, 0.10%, 0.12%, and 0.15% as a replacement for cement. The various mix proportions utilized in this study are shown in Table\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMix proportion for M40, M40-GGBS, M40-fly ash concrete\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eMaterial\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eM40\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eM40-GGBS\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eM40-fly ash\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eM1\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eM2\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eM3\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u003cp\u003eQuantity (kg/m\u0026sup3;)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCement (OPC 53)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e430\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e258\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e301\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGGBS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e172\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFly ash\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e129\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWater\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFine Aggregate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e728\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCoarse Aggregate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1189\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1189\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1189\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e(W/C)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSuperplasticizer (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab8\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 8\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMix proportion for M40-CNT concrete\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMix ID\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCNT Dosage\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCement (kg/m\u0026sup3;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eWater (kg/m\u0026sup3;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eFine Aggregate (kg/m\u0026sup3;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCoarse Aggregate (kg/m\u0026sup3;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eSuper plasticizer (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eCNT (kg/m\u0026sup3;)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eM4-1\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.01% CNT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e430\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1189\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.043\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eM4-2\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.03% CNT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e430\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1189\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.129\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eM4-3\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.05% CNT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e430\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1189\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.215\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eM4-4\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.08% CNT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e430\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1189\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.344\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eM4-5\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.10% CNT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e430\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1189\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.43\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eM4-6\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.12% CNT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e430\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1189\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.516\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eM4-7\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.15% CNT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e430\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1189\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.645\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Preparation of test specimen\u003c/h2\u003e\u003cp\u003eA freshly prepared concrete mixture is poured into cube, cylinder, and prism molds as shown in Fig.\u0026nbsp;2\u0026ndash;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The specimens were cast according to IS: 516\u0026ndash;2021 and IS: 516\u0026ndash;2021 for making specimen for various tests using steel molds, compacted in three even layers with a table vibrator to provide external vibration in accordance with IS: 2514 for ensuring sufficient compaction of the concrete. After casting, the samples are kept at room temperature (~\u0026thinsp;27\u0026deg;C) for moist curing, prior to testing. The samples were subjected to water curing until testing at 3, 7 and 28 days.\u003c/p\u003e\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Experimentations\u003c/h2\u003e\u003cp\u003eThe various tests were designed and conducted adopting American Society for Testing and Materials (ASTM), Bureau of Indian Standards (BIS) and recommendations from the ACI Committee.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section3\"\u003e\u003ch2\u003e2.4.1 Compression testing\u003c/h2\u003e\u003cp\u003eA cube specimen of dimensions 150 x 150 x 150mm was cast and tested at 3, 7 and 28 days of curing to assess the compressive strength of M40, M40-GGBS, M40-fly ash, and M40-CNT concrete. The examination was conducted following the standards IS: 516\u0026ndash;2021 and ACI 544.2R, using a Universal Testing Machine (UTM) capable of 1000kN and with a least count of 1kN, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The three samples are tested to find the average compressive strength of each concrete mix.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\u003ch2\u003e2.4.2 Split Tensile Testing\u003c/h2\u003e\u003cp\u003eA cylindrical sample with a height of 200m and a diameter of 100mm was cast and tested at 3, 7 and 28 days of curing to measure the split tensile strength of M40, M40-GGBS, M40-fly ash and M40-CNT concrete. The test was carried out on a cylindrical sample by placing it horizontally between the loading surfaces of the UTM, and the load was applied until failure in accordance with IS 516: 2021, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The three samples are tested to calculate the mean split tensile strength for each concrete mix.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\u003ch2\u003e2.4.3 Flexural testing\u003c/h2\u003e\u003cp\u003eA prism sample sized 100 mm x 100 mm x 500 mm was cast and tested at 7 and 28 days of curing to assess the flexural strength of M40, M40-GGBS, M40-fly ash, and M40-CNT concrete. The test was carried out following the guidelines of ASTM C78/C78M-21 under four-point loading on a simply supported length of 400mm utilizing a servo-controlled UTM with a capacity of 1000 kN, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The three samples are tested to find the average flexural strength for each concrete mixture.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\u003ch2\u003e2.4.4 Water Penetration Test\u003c/h2\u003e\u003cp\u003eThe water penetration of a concrete sample was typically conducted in accordance with standards such as EN 12390-8 or DIN 1048. This test assesses the depth to which water penetrates a concrete specimen under pressure, which indicates the concrete\u0026rsquo;s resistance to water ingress and overall durability. The test begins with the preparation of concrete specimens, usually cubes or cylinders measuring 150 mm \u0026times; 150 mm \u0026times; 150 mm. After casting, the specimens are cured in water for 28 days at a controlled temperature of 20\u0026deg;C\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C. Once cured, the surface moisture is allowed to dry naturally without oven-drying, as this can affect the test outcome. The dried specimen is then mounted in a water permeability cell so that one face is exposed to pressurized water, while the remaining faces are sealed using rubber gaskets to prevent edge leakage. Water pressure, typically 5 bar (0.5 MPa), is applied continuously for 72 hours using a pressure pump connected to a water reservoir. During this period, it is essential to maintain constant pressure and check that any water leakage occurs only through the concrete specimen and not due to improper sealing. After 72 hours of pressurized exposure, the sample is removed from the apparatus and split vertically through its center using a compressive testing machine or splitting device. The internal surface of the specimen reveals a darkened zone indicating the depth of water penetration. This depth is measured at three points using a ruler or vernier calliper, and the average of these measurements is recorded in millimetres.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\u003ch2\u003e2.4.5 Rapid Chloride Penetration test (RCPT)\u003c/h2\u003e\u003cp\u003eThe Rapid Chloride Penetration test (RCPT) was utilized to assess the resistance to chloride ion ingress of concrete modified with fly ash, GGBS and CNT as per ASTM C1202 standards as presented in Table\u0026nbsp;\u003cspan refid=\"Tab9\" class=\"InternalRef\"\u003e9\u003c/span\u003e. The concrete test specimen utilized for this test measured 50 mm in thickness and had a diameter of 100 mm. The test sample was set for 28 days. The concrete specimens were undergone vacuum saturation after 28 days of curing. Following the saturation of the samples, a non-conductive layer was added to the test samples. Next, the sample was positioned between the two cells of the RCPT test device as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, where one cell is filled with sodium chloride (NaCl) solution and the other cell is filled with sodium hydroxide (NaOH) solution. A direct current (DC) of 60 volts was utilized across the two cells for a duration of 6 hours.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab9\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 9\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eRCPT Ratings as per ASTM C1202\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCharge Passed (Coulombs)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChloride Ion Penetrability\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;4000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eHigh\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2000\u0026ndash;4000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eModerate\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1000\u0026ndash;2000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e100\u0026ndash;1000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eVery Low\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNegligible\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"3. Results and Discussions","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Compressive strength of concrete\u003c/h2\u003e\u003cp\u003eThe compressive strength results of concrete mixes that included GGBS, Fly Ash and carbon nanotubes (CNTs) tested after 3, 7 and 28 days was illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e9\u003c/span\u003e. At 3 days, it was observed that M1 (control mix) possesses a compressive strength of 37.5 N/mm\u0026sup2;, M2 (GGBS concrete) possesses a 32 N/mm\u0026sup2; and M3 (Fly Ash concrete) possesses a 27 N/mm\u0026sup2;. On the other hand, CNT-modified mixes significantly improved compressive strength as compared to fly and GGBS modified concrete. The highest compressive strength was observed for M4-2 (CNT 0.03%) at 40.5 N/mm\u0026sup2;, which is about a 26.56% and 50% higher than the compressive strength of GGBS and fly ash modified concrete. It seems that the CNTs contribute significantly to early strength development, likely due to their ability to accelerate cement hydration through enhanced nucleation sites and improved particle dispersion (Gao et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; MacLeod et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Guo et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). In addition, other CNT mixes such as M4-1, M4-3, M4-4 and M4-6 exhibits better strength than GGBS and fly ash-modified concrete at 3 days, which ranges from 21.88\u0026ndash;44.44%. It was observed that the fly ash modified concrete exhibits the lesser strength at 3 days due to its slower pozzolanic reaction, which typically gains strength at later ages. At 3 days, it was observed that M1 (control mix) possesses a compressive strength of 48.5 N/mm\u0026sup2;, M2 (GGBS concrete) possesses a 44.5 N/mm\u0026sup2; and M3 (Fly Ash concrete) possesses a 35 N/mm\u0026sup2;. On the other hand, CNT-modified mixes significantly improved compressive strength as compared to fly and GGBS modified concrete. The M4-1 (CNT 0.01%) possesses a compressive strength of 54.5 N/mm\u0026sup2;, which is about 22.47% and 55.71% higher than M2 and M3 mixes. The M4-2 (CNT 0.03%) possesses a compressive strength of 52.5 N/mm\u0026sup2;, which is about 17.97% and 50% higher than M2 and M3 mixes. These results strongly suggest that even small additions of CNTs can significantly boost strength in the early curing stages. However, mixes with higher CNT contents (e.g., M4-5 at 0.10%) started to show reduced effectiveness, indicating that excessive CNTs may lead to agglomeration and poor dispersion, which can negatively impact the mechanical performance of the concrete (Sobolkina et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Chen et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Rubel et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Reis et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). At 28 days, it was observed that M1 (control mix) possesses a compressive strength of 60 N/mm\u0026sup2;, M2 (GGBS concrete) possesses a 64 N/mm\u0026sup2; and M3 (Fly Ash concrete) possesses a 52 N/mm\u0026sup2;. The M4-2 (CNT 0.03%) mix possess a highest compressive strength of 65.5 N/mm\u0026sup2;, which is about 2.34% and 25.96% higher than M2 and M3 mixes. Essentially, several other CNTs added mixes such as M4-3 and M4-6 possesses matched or slightly exceeded strength, of M2 mixes, indicating that properly dosed CNTs can maintain long-term strength without compromising performance. On the other hand, M4-5 and M4-7 mixes gave poorer results compared to M2 mix, further confirming that CNT dosage must be optimized to avoid negative effects such as weak matrix due to clustering. On the other hand, GGBS modified concrete mix showed consistent long-term strength due to the continuation of its latent hydraulic reaction, making it a reliable choice for structural applications requiring gradual strength gain. Fly ash-modified concrete mix possesses poor compressive strength across all ages, despite some improvement over time, reflecting its delayed pozzolanic activity. The CNT-modified concrete significantly outperformed both GGBS- modified concrete and Fly Ash- modified concrete in terms of early-age strength. While long-term strength at 28 days was similar to GGBS concrete, the primary advantage of CNTs lies in their ability to enhance early strength development. The findings concluded that compared to Fly Ash, the CNT-modified concrete was superior across all time frames, emphasizing its potential as a high-performance additive when used at optimal dosages (especially around 0.03%).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Split tensile strength of concrete\u003c/h2\u003e\u003cp\u003eThe split tensile strength results of concrete mixes that included GGBS, Fly Ash and carbon nanotubes (CNTs) tested after 3, 7 and 28 days was illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e10\u003c/span\u003e. At 3 days, the GGBS-modified concrete mix and fly ash-modified concrete mix such as M2 and M3 possess a split tensile strength of 3.96 N/mm\u0026sup2; and 3.63 N/mm\u0026sup2;. It was observed that the split tensile strength of CNT modified concrete mixes are higher than of GGBS-modified concrete mix and fly ash-modified concrete mixes. The highest split tensile strength of 4.45 N/mm was obtained for the M4-2 mix which is found to be 12.37% and 22.58% higher than the GGBS-modified concrete mix (M2) and fly ash-modified concrete mix (M3). Similarly, mixes like M4-1, M4-3, M4-4, and M4-6 each achieved 4.37 N/mm\u0026sup2;, resulting in more than 10% improvement over GGBS and over 20% over Fly Ash. Even mixes with higher CNT content, such as M4-5 and M4-7, showed modest gains over GGBS and noticeable improvements over Fly Ash, although the rate of increase reduced slightly, suggesting potential dispersion issues at higher CNT dosages. These findings highlight the capacity of CNT to improve early-age tensile performance by acting as nucleation sites and bridging microcracks, enhancing the internal structure of the concrete. At 7 days, the GGBS-modified concrete mix and fly ash-modified concrete mix such as M2 and M3 possess a split tensile strength of 4.64 N/mm\u0026sup2; and 4.14 N/mm\u0026sup2;. Further, the CNT mixes continued to show better performance, with M4-1 achieving the highest tensile strength of 5.16 N/mm\u0026sup2;, which is 11.21% and 24.64% higher than GGBS-modified concrete mix (M2) and fly ash-modified concrete mix (M3). M4-2, M4-3, and M4-4 also demonstrated significant improvements, each exceeding GGBS modified concrete by over 8% and Fly Ash by more than 21%. M4-5 (0.10% CNT) was slightly below GGBS modified concrete, indicating that beyond certain CNT content, the benefits may decrease. However, all CNT mixes offer superior tensile performance as compared to fly ash-modified concrete mix (M3), reflecting its limited early strength due to the delayed pozzolanic reaction. At 28 days, GGBS-modified concrete reached a tensile strength of 5.60 N/mm\u0026sup2;, slightly outperforming the control (M1) and remaining well ahead of fly ash-modified concrete, which reached 5.05 N/mm\u0026sup2;. The CNT concrete with 0.03% CNT (M4-2) exhibited the highest split tensile strength at 5.66 N/mm\u0026sup2;, slightly surpassing GGBS by 1.07% and exceeding fly ash-modified concrete by 12.08%. M4-3 and M4-6 also performed marginally better than GGBS-modified concrete, while other mixes like M4-1, M4-4, and M4-7 closely matched or slightly underperformed GGBS-modified concrete. Although the differences at 28 days were modest, CNT mixes still demonstrated significant improvement over fly Ash-modified concrete, which remained the weakest performer. The CNT-modified concretes showed considerable improvements in split tensile strength at all ages compared to both GGBS and Fly Ash concretes. While GGBS concrete exhibited solid long-term performance, CNTs delivered more pronounced benefits at early stages, making them especially valuable for applications requiring rapid strength gain. Fly Ash concrete consistently displayed the lowest strength values, confirming its slower strength development. The optimum CNT dosage was found to be around 0.03%, beyond which efficiency began to decline, likely due to particle agglomeration and poor dispersion. These findings concluded that when used in optimal proportions, CNTs can significantly enhance the tensile properties of concrete, offering a promising solution for high-performance, early-strength applications.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Flexural strength of concrete\u003c/h2\u003e\u003cp\u003eThe flexural strength results of concrete mixes that included GGBS, Fly Ash and carbon nanotubes (CNTs) tested after 7 and 28 days was illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e11\u003c/span\u003e. At 7 days, GGBS modified concrete (M2) recorded a flexural strength of 4.25 N/mm\u0026sup2;, slightly higher than fly ash modified concrete (M3), which had 4.21 N/mm\u0026sup2;. However, CNT-enhanced concretes showed notable improvements. The highest strength at this age was achieved by the mix containing 0.03% CNT (M4-2), with 5.90 N/mm\u0026sup2;, representing a 38.82% increase over GGBS and 40.14% over Fly Ash. Other CNT mixes also outperformed GGBS and Fly Ash, with M4-6 (0.12% CNT) showing a 27.53% increase over GGBS, and M4-5 (0.10% CNT) and M4-3 (0.05% CNT) showing increases of 9.65% and 15.29% respectively. These results highlight the significant enhancement in early-age flexural strength due to CNTs, likely attributed to their ability to bridge microcracks, enhance bonding within the cement matrix, and improve the overall load transfer capability of the composite. After 28 days, the pattern of enhanced flexural strength in CNT mixtures persisted. The GGBS-modified concrete attained 4.82 N/mm\u0026sup2;, slightly exceeding the flexural strength of fly ash modified concrete of 4.78 N/mm\u0026sup2;. Once more, CNT-modified mixes exceeded both, with M4-2 (0.03% CNT) recording the peak strength of 6.65 N/mm\u0026sup2;, reflecting a 37.97% rise compared to GGBS modified concrete and a 39.12% increase over fly ash modified concrete mixes. Other mixes like M4-6 (0.12% CNT) and M4-5 (0.10% CNT) achieved 6.49 N/mm\u0026sup2; and 6.11 N/mm\u0026sup2;, demonstrating enhancements of 34.65% and 26.77% compared to GGBS, respectively. Even the least effective CNT blend (M4-7 with 0.15% CNT) showed a 14.52% improvement compared to GGBS. These findings suggest that CNTs play a crucial role in enhancing long-term flexural strength, particularly when utilized within an ideal range. The increase in strength is probably a result of the significant tensile capabilities of CNTs and their efficient interaction with the cement matrix, which improves crack resistance and overall structural integrity.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e3.4 Chloride penetration resistance of concrete\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab10\" class=\"InternalRef\"\u003e10\u003c/span\u003e presents the Rapid Chloride Penetration Test (RCPT) results for concrete mixes with varying percentages of carbon nanotubes (CNTs), which provide important insights into the influence of CNTs on chloride ion permeability and overall durability. As per ASTM C1202 standards, chloride ion penetrability is classified based on the charge passed in Coulombs: greater than 4000 is High, 2000\u0026ndash;4000 is Moderate, 1000\u0026ndash;2000 is Low, 100\u0026ndash;1000 is Very Low, and less than 100 is Negligible. Based on this standard, the CNT-modified concrete mixes are assessed and compared with the control (M1) for durability performance. The control mix M1 (0% CNT) recorded a charge passed of 1360 Coulombs, classifying it under \u0026ldquo;Low\u0026rdquo; chloride ion permeability, which corresponds to high durability. The incorporation of CNTs at low dosages further improved resistance to chloride ion ingress. For example, M4-1 (0.01% CNT) showed a reduced charge passed of 1297 Coulombs, while M4-2 (0.03% CNT) achieved 1192 Coulombs both still in the \u0026ldquo;Low\u0026rdquo; category but indicating improved performance over the control, with respective reductions of 4.63% and 12.35% in chloride permeability. These reductions reflect the densification of the cement matrix and crack-bridging ability of CNTs, which reduce the interconnected porosity. A significant improvement was observed in M4-3 (0.05% CNT), which had a charge passed of 890 Coulombs, falling into the \u0026ldquo;Very Low\u0026rdquo; chloride ion permeability category. This result marks a 34.56% decrease in permeability compared to the control and represents a shift to \u0026ldquo;Very High\u0026rdquo; durability, indicating that 0.05% CNT is an optimal dosage for enhancing resistance against chloride ion penetration. This improvement can be attributed to the effective dispersion and network formation of CNTs at this dosage, which significantly obstructs the movement of chloride ions by refining the pore structure and promoting secondary hydration. However, as the CNT content increased further, the performance trend fluctuated. For instance, M4-4 (0.08% CNT) exhibited a higher charge passed (1477 Coulombs) than the control, indicating a deterioration in permeability performance. This may be due to agglomeration of CNTs at higher concentrations, which can disrupt matrix homogeneity and increase localized porosity. Similarly, M4-6 (0.12% CNT) showed a charge of 1352 Coulombs, very close to the control, indicating no significant improvement, while M4-5 (0.10% CNT) and M4-7 (0.15% CNT) returned better results with 1154 Coulombs and 1143 Coulombs, respectively, both within the \u0026ldquo;Low\u0026rdquo; category but showing improved durability relative to M1. In summary, all CNT-modified concretes maintained at least \u0026ldquo;Low\u0026rdquo; chloride ion permeability according to ASTM C1202, ensuring high durability. The most substantial enhancement was observed at 0.05% CNT, where the mix achieved \u0026ldquo;Very Low\u0026rdquo; chloride ion permeability, representing the best performance in terms of durability. This suggests that optimal CNT dosage lies around 0.05%, beyond which the benefits plateau or decline due to dispersion challenges. Thus, CNTs, when used effectively, can significantly improve the durability of concrete by minimizing chloride ingress and enhancing microstructural integrity.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab10\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 10\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eRCPT values of various concrete mixes\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMix ID\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCoulomb\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eChloride ion Penetration level\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1360\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1297\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1192\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e890\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eVery Low\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1477\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1154\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1352\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003e3.4 Water penetration resistance of concrete\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab11\" class=\"InternalRef\"\u003e11\u003c/span\u003e presents the outcomes of water permeability test, which offer insights into the ability of concrete to withstand water infiltration, which is essential for durability, particularly in structures subjected to aggressive conditions. The control mix (M1) and mixes containing diverse percentages of carbon nanotubes (CNTs) demonstrate a distinct trend of performance enhancement attributed to the inclusion of CNTs. The control mix (M1) showed an average water penetration depth of 6 mm. This implies that the matrix contained localized weak spots or interconnected pores that allowed water ingress. In comparison, all CNT modified mixes demonstrated considerably enhanced water resistance, with most exhibiting zero or nearly zero permeability. The M4-1 (0.01% CNT) blend showed no water infiltration, yielding an average of 0 mm, clearly indicating better impermeability than the control. This pattern persisted in M4-5 (0.10%), M4-6 (0.12%), and M4-7 (0.15%), all of which similarly showed zero average penetration, demonstrating total resistance to water under the testing conditions. These findings indicate the beneficial effect of CNTs in decreasing capillary pores and filling microcracks, thus improving the impermeability of the concrete matrix. The M4-2 (0.03%) and M4-3 (0.05%) mixtures exhibited slight penetration, averaging 1 mm. The average penetration of M4-4 (0.08%) reached 2 mm which was still noticeably higher than that of the control. An increase in permeability observed in M4-4 may result from the CNTs were dispersed at that amount which led to regional micro voids or a non-uniform structure in the membrane. Adding CNTs reduced the water permeability by a lot, with average water penetration decreasing from 6 mm with the control mix to 0\u0026ndash;2 mm in the modified concretes. This leads to a better impermeability range of 83\u0026ndash;100%. In mixes with 0.01%, 0.10%, 0.12% and 0.15% CNTs, we observed full water resistance. The advantages from these CNTs lay in their ability to adjust the pore structure, fill nano-scale voids, and bridge microcracks, helping to make concrete denser and more impermeable. In conclusion, the water permeability test results that incorporating CNTs into concrete greatly improves its impermeability and the best effect can be seen with both lower and mid-range dosages of CNTs. This improvement in water tightness directly translates to increased resistance to deterioration mechanisms like corrosion, freeze-thaw cycles and sulfate attack, thereby greatly improving the long-term durability of concrete structures.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab11\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 11\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eWater penetration rate of concrete\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMix ID\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAverage Water penetration (mm)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4-7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThis study comprehensively evaluated the effects of incorporating Carbon Nanotubes (CNTs) into concrete, comparing them against GGBS and Fly Ash-modified concrete mixes. CNT-modified concretes showed significant improvements in all mechanical and durability measurements.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eCompressive strength increased by as much as 50% at 3 days, 55.71% at 7 days, and 25.96% at 28 days in comparison to Fly Ash concrete.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eTensile strength improvements reached 22.58% (3 days), 24.64% (7 days), and 12.08% (28 days) compared to Fly Ash concrete, with CNT mixes such as M4-2 (0.03%) exceeding the performance of all alternatives.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eFlexural strength demonstrated a 40.14% increase at 7 days and a 39.12% rise at 28 days, further validating the reinforcing properties of CNTs.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eDurability measurements showed comparable patterns. Chloride permeability reduced by 34.56%, moving from the \u0026ldquo;Low\u0026rdquo; to \u0026ldquo;Very Low\u0026rdquo; category according to ASTM C1202.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eWater permeability decreased by 83%-100%, with M4-1, M4-5, M4-6, and M4-7 reaching no penetration. However, an excessive CNT dosage (e.g., \u0026ge;\u0026thinsp;0.08%) caused performance declines of up to 8.6% because of particle agglomeration.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe findings determined that CNTs greatly improved both short-term and long-term performance, particularly within an optimal dosage range of 0.03% (M4-2 mix), providing a balanced boost in strength (up to 56%), impermeability (up to 100%), thus outperforming conventional additives such as GGBS and Fly Ash.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eG.C. Gandhi: Conceptualization, Methodology, Investigation, Data Curation, Formal Analysis, Writing - Original DraftP. Mehta: Supervision, Resources, Validation, Writing - Review \u0026amp; EditingA. Sodha: Visualization, Software, Formal Analysis, Writing - Review \u0026amp; Editing\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors sincerely express their gratitude to Unique Geo Civil Services Pvt. Ltd., Surat, Gujarat, for their technical support and cooperation throughout the experimental phase of this research. Special thanks are extended to KBM Engineering Research Laboratory, Ahmedabad, and Modi Laboratory, Ahmedabad, for providing essential testing facilities and infrastructure that significantly contributed to the successful execution of this study. The authors also wish to acknowledge Ms. Meena Lochani, Research Scholar, Indus University, Ahmedabad, for her valuable inputs and collaborative support during the data collection and analysis stages. Heartfelt appreciation is extended to Mr. Harshil Parikh, former Design Director, Larsen \u0026amp; Toubro, Dholera, for his insightful discussions and technical suggestions, which helped refine the structural aspects of the research. The authors are also grateful to Ms. Jyotsna Gautam, General Manager and Cluster Head (N \u0026amp; W), Larsen \u0026amp; Toubro, Ahmedabad, and Ms. Juhi Gandhi, Techno Commercial Manager of Adani Green, Ahmedabad for her encouragement and professional guidance, which played a vital role in shaping the practical relevance of the work.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analysed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbbass, M., Singh, D. \u0026amp; Singh, G. 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Status of coal-based thermal power plants, coal fly ash production, utilization in India and their emerging applications. \u003cem\u003eMinerals\u003c/em\u003e \u003cb\u003e12\u003c/b\u003e (12), 1503 (2022).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Ground Granulated Blast Furnace Slag (GGBS), Fly Ash (FA), Carbon Nanotubes (CNTs), Mechanical properties, Durability properties","lastPublishedDoi":"10.21203/rs.3.rs-7123791/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7123791/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eConcrete, the most commonly used construction materials, encounters issues because of its substantial cement content, leading to environmental harm, alongside limitations in strength and durability. This study examines the mechanical and durability properties of M40 grade concrete modified with Ground Granulated Blast Furnace Slag (GGBS), Fly Ash and Carbon Nanotubes (CNTs). Four types of mixes such as M40 (control), M40 incorporating 40% GGBS, M40 containing 30% Fly Ash and M40 with CNTs (0.01%-0.15%) distributed using supersonication in xylene were examined. The mechanical properties such as compressive, split tensile, and flexural strength were evaluated at 3, 7, and 28 days, in addition to durability tests conducted through Rapid Chloride Penetration and Water Permeability tests. The findings indicated that CNTs notably enhanced performance, especially at concentrations ranging from 0.03\u0026ndash;0.05%; especially, the compressive strength increases by 56%, tensile strength increases by around 20% and flexural strength enhanced by around 39% respectively as achieved for 0.03% CNTs. Furthermore, the durability of the CNTs modified concrete has also improved, achieving up to a 100% decrease in water permeability and a 34.56% reduction in chloride penetration. The study concluded that the GGBS- modified concrete outperformed Fly Ash- modified concrete, while CNTs- modified concrete provided the most significant improvements in mechanical and durability properties, showcasing their potential in sustainable concrete.\u003c/p\u003e","manuscriptTitle":"Performance Evaluation of M40 Grade Concrete With GGBS, Fly Ash, and Carbon Nanotube Admixtures: A Comparative Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-29 13:10:33","doi":"10.21203/rs.3.rs-7123791/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"14c22184-7455-4ad0-b7a8-8bc4e63ac94c","owner":[],"postedDate":"August 29th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":53904058,"name":"Physical sciences/Engineering"},{"id":53904059,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2025-09-02T11:38:58+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-29 13:10:33","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7123791","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7123791","identity":"rs-7123791","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}