Effect of Biological shells aggregate on the Mechanical properties and sustainability of concrete

Effect of Biological shells aggregate on the Mechanical properties and sustainability of concrete | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effect of Biological shells aggregate on the Mechanical properties and sustainability of concrete Xianpeng Wang, Fulong LI, Haoxuan Yu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4093653/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 09 May, 2024 Read the published version in Scientific Reports → Version 1 posted You are reading this latest preprint version Abstract To solve waste bio-shell and put them into recycle, the researchers proposed using waste bio-shells as aggregate matrix for concrete. In order to determine the substitution amount of shells, the researchers used the orthogonal experimental method, and designed shell concrete experiments with gradient substitution rates at 10%, 30% and 50%, with a total of 78 groups of specimens. By analyzing the tensile, bending and frost resistance of these specimens, the experimental data show that adding shells as aggregate at 10%, 30% or 50% can improve the mechanical properties of the concrete, the maximum flexural strength can be increased by 3.96Mpa, the maximum compressive strength can be increased by 2.5Mpa, but with a degradation of frost resistance. With the investigate of economic performance, it was found that the costs of frame-shear structure, frame structure, and tube-in-tube structure were reduced by 10.2%, 10%, and 10.3% respectively. In the carbon environmental assessment, the carbon reduction of a single specimen with 10%, 30%, and 50% shell addition were 0.003, 0.0010, and 0.0015 kg respectively. In summary, compared with ordinary concrete materials, it is very possible to use waste bio-shells as a substitute for aggregates to develop the sustainable recycling development of concrete materials. aggregate concrete shell aggregate mechanical properties carbon emission economic analysis 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 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 1. Introduction In recent years, the treatment of garbage problem has become serious all over the world, large amount of garbage has caused serious air pollution and ecological damage, as shown in Figs. 1 and 2 . In order to solve this problem, the researcher consider separating useful material from waste and using it in the research to develop new building materials. Therefore, the researchers have made relevant classification and composition screenings of the collected waste and found out that bio-shells, one of the kitchen waste, are good choice for replacing traditional concrete aggregates. As reported by previous researcher, nearly 10 million metric tons of shells of oysters, clams, scallops, and mussels are discarded globally every year. [ 2 ] Furthermore, a comprehensive survey was carried out to assess the situation of restaurants in selected provinces of China and the Republic of Belarus, the collected data revealed that the Belarusian restaurant chain brand "Sea Food" alone generates amounting to over 100 catties discarded seashells per day. Correspondingly, approximately 5 tons of seashells are discarded daily in the provinces Guangdong and Fujian, China. [ 3 ] To address the pollution problem, analyzing the chemical composition and potential use of shells as building materials is very necessary. The results show that shells contain calcium carbonate, glycoprotein, proteoglycan, polysaccharide, and chitin. In the hydration process of cement, water reacts with four main clinker minerals. At room temperature, tricalcium silicate hydrates to form calcium silicate hydrate (C-S-H gel) and calcium hydroxide, while dicalcium silicate (β-C2S) hydrates to produce similar products. Tricalcium aluminate hydrates to form unstable calcium aluminate hydrate, which eventually transforms into hydrogarnet (C3AH6). The hydration reaction of iron phase solid solution (C4AF) is similar to that of tricalcium aluminate [ 4 ] . By observing the hydration reaction, the researcher can conclude that shells do not affect the hydration process of cement, and thus do not cause damage to the structure and strength of concrete. Therefore, the researchers think that shells can be used as part of concrete aggregates to develop new building materials. In coastal regions, the primary source of construction sand is desalinated sea sand, which typically contains a shell content of 5%~8%. From a research of mortar, the incorporation of shells in place of river sand has a notable influence on the overall compressive strength and dry shrinkage of cement-based materials, with an increase of 8% in the proportion of shells [ 5 ] . Mr. Yang has focused on studying shell aggregates as an alternative to natural aggregates. Yang's research suggests that shell aggregates hold promising potential for practical applications, offering a favorable solution to the growing shortage of natural aggregate resources. Dr. MO asserts that there is a growing inclination towards sustainability in the field of concrete engineering, primarily driven by the depletion of materials traditionally employed in the production of natural concrete. It is suggested that utilizing shell waste in the production of concrete can enhance both its workability and strength, thereby offering a viable solution [ 5 ] . Kuo's experiments proposed that replacing a portion of river sand with shells in cement can lead to an increase in the proportion of shells. This substitution has had a notable impact on the overall compressive strength and shrinkage of the base material [ 6 , 7 ] . Eziefula has found that shells can be used as a partial or total substitute for fine and coarse aggregates in concrete [ 8 ] . Some scholars in China used shells as aggregates to test concrete and found that the compressive strength of concrete increased with the raise in shell replacement rate after 28 days. [ 9 ] . Sergey’s study showed that shells improved the strength, strain, modulus, and microstructure of concrete. The new concrete also reduced the cost and defects of construction. This research has practical implications. [ 10 ] . Belarus researchers tested to use agricultural waste (e.g., rice husk ash, peanut shells, oak wood chips, coconut shells, and corn cobs) as aggregate substitutes. This can lower waste pollution to environment and construction costs [ 11 ][ 12 ] . Many studies have tested shells in concrete. From those tests, shells have more advantages over other agricultural wastes as concrete aggregates. Martínez found that shells should not exceed 25% for fine aggregates and 12.5% for coarse aggregates to improve concrete strength [ 13 ] . Malaysian researchers have suggested that Calcined shells improve concrete strength and density. Future research should test different calcination levels and shell concrete durability. [ 14 ] In addition, according to the research of Iraqi scholars, similar to shells, crushed walnut shell is an agricultural waste material that can be used to produce environmental concrete that reduces the demand for natural aggregates and the environmental impact of concrete production [ 15 ][ 16 ][ 17 ] . After a thorough review of the above studies, our team concluded that shells possess exceptional mechanical properties [ 18 ] , a significant specific surface area, and a lower density compared to stone. As a building material, shells offer advantages such as workability, strength, and reduced weight in concrete [ 19 ] . To prepare the shells, they should be soaked in a concentrated solution of NaCl and a diluted solution of 10% H 2 O 2 [ 20 ] , after removing organism and impurities, the material is crushed and screened to produce shells with a particle size of less than 0.5mm. This not only helps save resources and energy but also reduces waste and decreases the consumption of natural aggregates [ 21 ][ 22 ] . As a result, it creates greater economic and social benefits [ 7 ][ 9 ][ 23 ] . Additionally, the study suggests that using the right amount of shell aggregate can enhance the strength of concrete, ensuring the safety and stability of structures while promoting sustainable development [ 24 ] . Previous studies have shown that shells have adequate strength and some superior properties as aggregates [ 13 ] . However, there is no consensus on the best way to use shells in construction, and few practical examples exist. Our team planned to test three levels of calcined shells (10%, 30%, and 50%) as aggregate replacements and compare their mechanical, economic, and environmental performance with conventional concrete. 2. Experimental program This experiment uses different proportions of shells as concrete aggregate, prepares cement mortar according to a certain mix ratio and curing conditions, uses different test equipment and methods to measure its compressive strength, flexural strength and water absorption rate, in order to study the effect of shell replacement of crushed stone on the performance of cement mortar. 2.1 Experimental materials and proportions 2.1.1 The performance of the shell Shells are the hard protective coverings of various mollusks, such as oysters, clams, mussels, and scallops. They are composed mainly of calcium carbonate, also known as limestone, which is a common ingredient of cement [ 19 ] . Shells have a complex hierarchical structure, consisting of different layers of organic and inorganic materials, arranged in various patterns and orientations. This gives them high strength and toughness, as well as resistance to fracture and damage [ 25 ] . The properties of seashell concrete depend on several factors, such as the type, size, shape, and proportion of seashells, as well as the curing conditions, admixtures, and chemical treatments. Some of the effects of seashells on concrete are: Setting time: Seashells can increase the setting time of concrete, due to their alkaline nature and water absorption capacity [ 25 ][ 26 ] . Workability: Seashells can decrease the workability of concrete, due to their irregular shape and rough surface [ 25 ] . Density: Seashells can increase the density of concrete, due to their higher specific gravity than cement or sand [ 25 ][ 26 ] . Compressive strength: Seashells can decrease the compressive strength of concrete, due to their lower bonding strength with cement paste and higher porosity 234. However, adding admixtures or applying chemical treatments can improve the compressive strength of seashell concrete [ 26 ][ 27 ] . Tensile strength: Seashells can increase the tensile strength of concrete, due to their fibrous structure and crack-bridging effect [ 13 ][ 25 ] . Flexural strength: Seashells can increase the flexural strength of concrete, due to their higher modulus of elasticity and toughness [ 26 ] . Modulus of elasticity: Seashells can decrease the modulus of elasticity of concrete, due to their lower stiffness and higher deformation [ 27 ] . 2.1.2 Experimental materials Table 1 The main component of cement % CaO SiO2 Al2O3 Fe2O3 SO3 Na2O K2O MgO 64.12 22.31 6.42 4.37 1.1 0.75 0.56 0.37 Table 2 Physical and mechanical properties of cement Standard Consistency Water Requirement/% Specific surface area/ (m2/kg) Coagulation time/min Compressive strength/MPa Flexural strength/MPa Initial setting Finalization 3 d 28 d 3 d 28 d 28 360 175 235 27.5 49.0 5.5 8.0 Cement: P·O R45 cement, The main chemical composition is presented in Table 1 , while the physical and mechanical properties are displayed in Table 2 , which complies with the requirements of EN 197-1 for chemical composition, strength, setting time, soundness, and fineness. Water: ordinary tap water. Sand: natural river sand, in line with the construction sand standard, the bulk density is less than 1.5g/m 3 , the fineness modulus is 1.9, the moisture content is less than 1%. Stone: fine stone meets the requirements of EN 12620 for geometrical and physical properties, the bulk density is not less than 2.6g/m 3 , the particle size is 5mm- 7mm. Shell: according to the European Standards (EN − 12620), the aggregates used in the production of concrete are inert granular materials such as gravel, crushed stone, sand, slag, recycled concrete, and geosynthetic aggregates. The aggregates may be natural, manufactured, or recycled, hence, the substitution of shells for aggregate meets the standards. After calcination and crushing, the particle size is less than 0.5mm, the bulk density is less than 2.9g/m 3 , the fineness modulus is 2.9, and the moisture content is less than 1%, refer to Fig. 3 and Fig. 4 for details. The compressive strength of the concrete samples was tested at 7 days and 28 days after casting, according to EN 12390-3. The average compressive strength at 7 days was 25 MPa, 35 MPa on 28 days, which met the design requirement of 30 MPa for the structural elements. The slump test was performed on the fresh concrete mix, according to EN 12350-2. The slump value was 75 mm, which indicated a medium workability of the concrete, suitable for the casting and compaction methods used in this project. 2.1.3 Material ratio and specimen design According to the study's conclusions and curve analysis, it is believed that as the water-binder ratio increases, the impact of coarse aggregate becomes more pronounced, resulting in lower dry shrinkage [ 28 ] , refer Fig. 5 . According to the studies of previous researchers, increasing the water-cement ratio results in higher porosity and lower strength of the concrete [ 29 ] . After analyzing Figs. 5 and 6 , and considering EU standard EN 206 + A2 and Chinese standard GB 50010 − 2010, the water-cement ratio in the range of 0.45–0.6 is relatively appropriate [ 30 ] , to ensure sufficient strength and reduce porosity, it is necessary to choose a smaller water-cement ratio [ 31 ] . So our team take a water-cement ratio of 0.5 as optimal for ensuring the strength and preventing cracking of the concrete in the experiment [ 31 ][ 32 ] . In this test, shells and other materials were used as a substitute for natural stone. The mix ratio (kg/m3) of the cement mortar in the benchmark group was as follows: m (cement): m (sand): m (stone): m (water) = 500: 600: 900: 250, the mix ratio (kg/m3) of the cement mortar in the 10% shell replacement rate was as follows: m (cement): m (sand): m (stone) : m(shell): m (water) = 500: 600: 810:90: 250, the mix ratio (kg/m3) of the cement mortar in the 30% shell replacement rate was as follows: m (cement): m (sand): m (stone) : m(shell): m (water) = 500: 600: 530: 270: 250, the mix ratio (kg/m3) of the cement mortar in the 50% shell replacement rate was as follows: m (cement): m (sand): m (stone) : m(shell): m (water) = 500: 600: 450: 450: 250. All the mixes conform to standard EN 206-1, the mixture is shown in Fig. 7 . Additionally, the superplasticizer content was 0.2% of the cement mass. The gravel is replaced based on shell gradients of 10%, 30%, and 50%. The mixture was evenly stirred and poured into a mold with dimensions of 400 mm×400 mm×1600 mm, the test prisms is shown in Fig. 8 , followed standard EN 12390-5:2009. Thirteen specimens are cast for each different gradients, 39 specimens in total for bending experiments. The specimens for compressive experiments are 100 mm×100 mm×100 mm, followed the standard EN 12390-3:2019, with 13 specimens cast at the each gradient, 39 specimens in all. After segmental vibration compaction, the specimens were hardened at 23°C, demoulded after 7 days, and cured at 20°C with a relative humidity of 95% until the specified age [ 33 ] . 2.1.4 Experimental procedure After curing for 28 days, the specimen underwent test using the DS2-1000N compressive strength tester for axial compressive resistance and three-point bending. The "Hydraulic Pressure Testing Machine-GB/T3722" was used to conduct a uniaxial compressive test on the specimen, aligning the axis with the pressure center of the testing machine's pressure plate. The load was applied at a speed of 10 kN/s to 30 kN/s until the specimen failed, and the failure load was recorded to determine the compressive and flexural strengths [ 33 ] . The test block was soaked in water for 2 days, taken out to dry completely, recorded the weight before and after. The water absorption rate was calculated to evaluate the frost resistance strength. 3. Experimental results and analysis 3.1 Flexural strength The failure load of the specimen was obtained through a three-point bending test, testing followed the third point loading because it is simpler to perform and analyze than the fourth point loading [ 34 ] . The testing were following the standard ASTM C78/C78M and the flexural strength is presented in Table 3 , and the flexural strength ff (MPa) of the specimen is calculated according to the formula \({\varvec{f}}_{\varvec{f}}=\frac{\varvec{F}\varvec{l}}{\varvec{b}{\varvec{h}}^{2}}\) , the testing is shown in Fig. 9 , where ff is the concrete flexural strength (MPa), F is the failure load of the specimen (N), L is the span between the supports (mm), and b is the cross-sectional width of the specimen (mm), h is the cross-sectional height of the specimen (mm); the scatter plot distribution of flexural strength is shown in Fig. 10 . Table 3 Concrete flexural strength under different substitution rates Shell replacement rate/%. Flexural strength f f (MPa). 0 (Standard Group) 6.5 6.25 5.25 6.5 6.5 5.75 10 7.5 9.5 14.25 7.75 8 7.5 30 9.75 9.75 9.75 8.5 9.25 9 50 9.75 10 10 10.25 10.5 10 3.2 Compressive strength Through the uniaxial compressive test, the uniaxial compressive failure load of the specimen is determined, and the compressive strength fc(MPa) of the test cube can be calculated according to the formula \({\varvec{f}}_{\varvec{c}}=\varvec{F}/\varvec{A}\) , here fc is the compressive strength, F is the failure load, and A is the bearing area. Intensity data is presented in Table 4 . The scatter plot distribution of compressive strength is shown in Fig. 11 . The damage situation is depicted in Fig. 13 . Table 4 Compressive strength of concrete under different replacement rates Shell replacement ratio/% Compressive strength fc (MPa). 0 (Standard Group) 20.4 19.5 20 20.6 20.3 18.8 10 23.4 21.3 22.4 22.2 21.6 22.8 30 22.5 22.9 22.8 20.3 22.4 22.5 50 21.8 22.6 21.9 22.3 23.3 22.9 3.3 Microstructure analysis In order to carry out a more comprehensive analysis of the impact of shell aggregates on the mechanical properties of concrete at a microscopic level, the researcher performed scanning electron microscopy (SEM) on shell aggregates with varying replacement rates (0%, 10%, 30%, and 50%). This allowed us to observe the surface structure of the concrete under different shell replacement conditions. Figure 14 a depicts concrete without shell aggregate, Fig. 14 b illustrates concrete with a 10% shell aggregate. In Fig. 14 c, concrete with a 30% shell aggregate is shown, and Fig. 14 d displays concrete with a 50% shell replacement rate. By comparing these four sets of images, it is evident that the inclusion of shell aggregate in concrete enhances the compactness of the joints between concrete structures, resulting in improved stress performance and a reduced risk of compressive cracking. Consequently, the overall working performance of the concrete is enhanced. 3.4 Waters absorption ratio After measuring the mass of the samples before and after, the water absorption rate can be calculated by formula \(\varvec{W}=(\varvec{B}-\varvec{G})/\varvec{G}\times 100\varvec{\%}\) , G is the weight of the sample after drying, B is the weight of the sample saturated with water, the testing method was according to the EN 12390-8:2009, and the data is presented in Table 5 . The curve depicting the change in water absorption is shown in Fig. 12 . Table 5 Concrete moisture content under different substitution rates Shell replacement ratio/% Weight before tumbling/g Weight after drying/g Water absorption/% 0 (Standard Group) 634.5 614.4 3.27 10 607.1 576.8 5.25 30 609.8 582.9 4.61 50 601.2 573.7 4.79 4. Prediction of the mechanical strengths Based on the analysis of the data obtained from the three-point flexural test (Table 3 ), the researcher get the following conclusions: when the shell replacement rate is 10%, the flexural strength of the specimen increases by 31.4% and 1.925MPa compared to the benchmark group. When the shell replacement rate is 30%, the flexural strength of the specimen increases by 52.4% and 3.208MPa compared to the benchmark group. The flexural strength of the specimen increases by 64.6% and 3.958MPa respectively when the shell replacement rate is 50%. According to the mechanical curve shown in Fig. 10 , it is evident that the addition of the shell significantly enhances the flexural strength of the prism when compared to traditional aggregate. This indicates that the inclusion of shell aggregate reduces the concrete's susceptibility to bending and fracturing. Consistent with the experimental phenomenon, previous research has shown that the addition of shells improves post-cracking behavior, reduces the opening of cracks, and counteracts their expansion, as well as increases the toughness of concrete owing to their deboning and internal stresses mechanisms [ 35 ][ 36 ] . Furthermore, due to the adsorption capacity of shells [ 37 ] ,when the shell is aligned with the tensile direction, it is capable of bearing the tensile force and impeding crack propagation [ 38 ] . Therefore, the shells with higher content have a wider and more uniform distribution in the concrete, as the cement does not have a significant effect on the shells during the hydration process, and no settlement or floating occurs, which also improves the tensile strength of the concrete. These findings are supported by the available data, when the shell replacement rates were 10%, 20%, and 30% respectively, the mixing ratio increased by 10% each time, and the 90 d tensile strength of the concrete with traditional aggregate increased by 11.8%, 15.1%, and 17.6% respectively. [ 6 ][ 8 ][ 25 ][ 35 ] . In the uniaxial compressive test (Table 4 ), it was observed that the compressive strength of the specimen increased by 10.7% and 2.727MPa when the shell replacement rate was 10% compared to the benchmark group. Similarly, when the shell replacement rate was 30%, the compressive strength of the specimen increased by 16.6% and 3.207MPa compared to the benchmark group. The compressive strength of the specimen increased by 17.8% and 3.442MPa compared to the benchmark group when the shell replacement rate was 50%. With check of the curve depicted in Fig. 11 , it is evident that the inclusion of shell aggregates leads to a significant enhancement in compressive strength. This observation suggests that the addition of shell aggregates improves the concrete's resistance to compression-induced damage and enhances its load-bearing capacity. Upon comparing the curves depicted in Figs. 10 and 11 , it is evident that the curve exhibits a rapid raise in the range of 0–30% replacement rate. However, the rate of increase slows down between 30% and 50%, and eventually reaches a plateau when it approaches 50%. This observation suggests that shells can be substituted at a rate as high as 50% while still providing satisfactory strength as aggregates. Figure 14 presents scanning electron microscope (SEM) images of shell concrete at a 28-day scale, depicting various shell aggregates with distinct gradients in intensity. Based on the captured images of moral onlookers, the researcher conducted a further analysis on the impact of shell aggregates on the mechanical properties of natural aggregates. Based on the SEM microscopic diagram of the failed samples, it can be observed that the cracking in the shell aggregate concrete with 0% content is more pronounced and the spacing between cracks is larger. In contrast, the shell aggregate concrete with 10% content exhibits significantly smaller fracture spacing compared to the 0% content. Moreover, the shell aggregate concrete with 30% and 50% content only shows a limited number of microcracks and pores, which can be considered the mechanically weak areas. Hence, it has been demonstrated that incorporating crushed shells into concrete under identical pressure conditions can effectively enhance the mechanical properties of the concrete. Further examination of Figs. 14 b, c, and d reveals that the concrete structure exhibits a high level of compactness, with no presence of a cementitious porous structure. This observation effectively demonstrates the favorable workability of the concrete material when shell aggregate is added as a composite material. Additionally, the shell aggregate is capable of forming a dense matrix structure with the natural aggregate, resulting in strong compactness and low porosity. This further enhances the bonding between the cement slurry and the aggregate matrix. Therefore, the incorporation of shell aggregate as a partial replacement for natural aggregate has been found to significantly enhance the mechanical properties of concrete. Cong proposed that there was a positive correlation between the moisture content of concrete and its higher frost resistance [ 39 ] . Therefore, it is hypothesized that the frost resistance of the test block may be influenced by its water absorption capacity, it can be considered that the lower water absorption rate, the more favorable frost resistance of the material [ 40 ] . It is expected that a lower water absorption rate would result in a lower moisture content within the test block, thereby enhancing its frost resistance [ 41 ] . Based on the analysis of the curves presented in Table 5 and Fig. 8 , it can be inferred that the replacement of traditional aggregate with shell leads to a slight increase in the moisture content of the test block. Consequently, it can be concluded that the frost resistance of the shell aggregate is poor. With the gradual increase in the replacement rate of aggregate, there is minimal fluctuation in the moisture content. It can be inferred that while the replacement rate of shell aggregate may decrease the frost resistance, varying replacement rates have a negligible impact on the frost resistance of concrete. Furthermore, in the process of experiment, it was observed that the application of mechanical vibration in the concrete exhibited a flow-like behavior, allowing it to evenly and densely fill the formwork. The destruction section displayed a uniform distribution of shells, with no instances of delamination or segregation. Additionally, it was noted that there were no significant issues with water leakage during the curing process. It can be inferred that the use of shells as aggregates exhibits favorable workability and integrity. 5. Life cycle assessment 5.1 Economical assessment The researchers believe that in the process of studying the replacement of traditional aggregates by shells, in order to explore the application of aggregates in actual production, it is very important to analyze its economic performance. Take the China Construction Project Budget Quota to calculate the cost of concrete: 180 yuan//m 3 for sand, 4.1 yuan/m 3 for commercial water, 635 yuan/ton for cement, 220 yuan/m 3 for stone, one cubic meter of concrete weighs 2400 kg. The cost of commercial concrete is 635 yuan/m 3[ 42 ] . In addition, the researchers investigated the garbage recycling plant and recycled the waste shells, found that the waste shells were biological waste, and the recycling plant believes that they do not have recycling value, so they can be obtained free of charge, and only need to issue relevant labor costs, and the cost of shells can be calculated according to the labor cost of 10 yuan per m³ [ 43 ] . 5.1.1 Economic performance analysis of buildings using frame shear structure The researchers take a significant high-rise building project covering a total area of 173,256.37 m 2 in East of China as a sample. The structure of the building is depicted in Fig. 15 . To assess the economic viability of shell aggregates, the researcher substituted all concrete materials with 50% shell aggregate concrete. Upon comparison with traditional aggregates, it was found that the total concrete consumption amounted to 82,226.37 m 3 . Full analysis details are given in Appendix 1. 5.1.2 Analysis of the economic performance of buildings using frame structures The researchers take a nine-storey frame structure in southern China as a sample, with a total area of 12055.52 m 2 (Fig. 16 ), to assess the economic performance of shell aggregates. An analysis was carried out by replacing all concrete with 50% shell aggregate concrete compared to traditional aggregates. The total concrete consumption for this structure amounted to 3389.92m 3 . Full analysis details are given in Appendix 2. 5.1.3 Analysis of the economic performance of the building using the tube in the tube The researchers take a building with a tube structure in southern China as a sample, as depicted in Fig. 17 , which has a total area of 341376.54 m 2 . To evaluate the economic performance of shell aggregate, an analysis is base on replacing all concrete with 50% shell aggregate concrete. The total volume of concrete used in this structure was 263,124.38 m 3 . Full analysis details are given in Appendix 3. Compare the cost of replacing traditional aggregates with shells in three building structures (Fig. 18 ), the researchers calculated that the concrete costs of the frame-shear structure, frame structure, and tube-in-tube structure are reduced by 10.2%, 10%, and 10.3% respectively. This suggests that shells aggregate can effectively reduce building costs. 5.2 Environmental assessment In order to assess the environmental impact of shell aggregates, it is important to consider carbon emissions. This includes the carbon emissions from the production of raw materials (C 1a ), which refers to the CO 2 generated during the production and processing of raw materials. This includes energy consumption and carbon emissions from the material processing itself. The calculation formula for C 1a is as follows: \({\varvec{C}}_{1\varvec{a}}=\sum _{\varvec{i}}\left(\sum _{\varvec{j}}{\varvec{a}}_{\varvec{i}\varvec{j}}{\varvec{K}}_{\varvec{j}}\right){\varvec{m}}_{\varvec{j}}+{\varvec{g}}_{1}{\varvec{m}}_{1}\) . In the formula, a ij represents the energy consumption of class j in the production process of class i raw materials. m j represents the amount of class I raw materials used in 1 m 3 of recycled concrete. k j is the carbon emission coefficient of class J energy, which is the sum of the direct carbon emission coefficient Kj and the indirect carbon emission coefficient K j . g 1 represents the carbon emission generated by the material itself in the process of cement production, m 1 represents the amount of cement in 1 m 3 of recycled concrete [ 44 ] . The study will utilize the mixture ratio of experimental test blocks to calculate parameters for carbon emissions. The calculation parameters for carbon emissions are presented in Table 6 , while Table 7 displays the carbon emissions resulting from energy consumption. Full analysis details are given in Appendix 4. Table 6 Carbon emission calculation parameters [ 44 ][ 45 ] Unit material Power Consumption/ (kW·h) Coal Consumption/ Kg Diesel Consumption/ L 1t cement 40 96 1t natural coarse aggregate 1.17 0.723 1t sand 1.5 0.8 1t water 0.29 Table 7 Carbon emissions generated by energy /kg Unit energy Direct carbon emissions Indirect carbon emissions Total carbon emissions 1kW h of electrical energy 0 1.195 1.195 1kg of coal 2.53 0.088 2.618 1L diesel 2.73 0.448 3.178 The carbon emission curve of concrete at different shell replacement rates suggests that incorporating shells, as shown in Fig. 19 , can effectively reduce carbon emissions. This reduces energy consumption and minimizes the environmental impact of buildings, protecting the ecological environment [ 46 ] . Conclusion The researchers tested mechanical properties of the concrete specimens with 10%, 30% and 50% crushed bio-shell as a replacement aggregate, calculated the concrete cost of three different types of building, and evaluated carbon environmental impact of the specimens using a carbon environmental protection formula. The main conclusions are summarized below: (1) The substitution rate of shell can reach up to 50%, and the higher the substitution rate within this range, the greater the enhancement in concrete strength. The maximum increase in flexural strength can reach 3.96 MPa, and the highest increase in compressive strength can reach 2.5 MPa. (2) After calculating the project's actual content, it was found that using shell aggregate concrete can reduce material costs by approximately 10% for various structural projects. This significantly addresses the issue of excessive project costs. (3) Based on a carbon environmental protection formula, we find that shell aggregate exhibits commendable environmental performance. In addition, This approach effectively mitigates kitchen waste disposal, reduces energy consumption, minimizes the environmental impact of carbon dioxide emissions, enhances the ecological environment, and ultimately yields significant social benefits. Declarations Authorship contribution statement Xianpeng Wang 1 ＊ : experiment, investigation, data management, methodology, formal analysis, conceptualization, writing-original draft, project administration. Haoxuan Yu 1 ＊ : experimentation, investigation, data validation, writing, review and editing. Fulong Li : Professor Li helped with the revision comments of the peer reviewers, reviewed the final version, and provided a lot of support for subsequent research materials. Kovshar Sergey Nikolayevich 1 : provide experimental materials, provide experimental help, review the final manuscript and edit comments, and supervise the entire experimental process. Haojue Yu 1 ,My colleague Yu Haojue has excellent English proficiency and has rigorously proofread the English grammar and civil engineering English vocabulary of the full text. Leonovich Sergey Nikolaevich 1 * : review, comment and edit, supervise, and verify data. Wenbing F:He made detailed revisions to the abstract and conclusion sections and provided great help in solving the reviewers' questions. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Data availability Data will be made available on request. Acknowledgement The first corresponding author, Ph.D student Xianpeng Wang, thanked the China Scholarship Council for the self-help in life. 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Environ Challenges 1:100004. https://doi.org/10.1016/j.envc.2020.100004 Nie H, Wang L, Tian M (2024) Analysis on determinants of carbon emissions from plaza ground paving during the construction stage based on life cycle assessment. Sci Rep 14:136. https://doi.org/10.1038/s41598-023-47933-9 Additional Declarations The authors declare no competing interests. Supplementary Files Appendix1Economicperformanceanalysisofbuildingsusingframeshearstructure.docx Appendix2Analysisoftheeconomicperformanceofbuildingsusingframestructures.docx Appendix3Analysisoftheeconomicperformanceofthebuildingusingthetubeinthetube.docx Appendix4carbonemissionsperformanceanalysis.docx Cite Share Download PDF Status: Published Journal Publication published 09 May, 2024 Read the published version in Scientific Reports → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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07:07:06","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":15480,"visible":true,"origin":"","legend":"","description":"","filename":"Appendix1Economicperformanceanalysisofbuildingsusingframeshearstructure.docx","url":"https://assets-eu.researchsquare.com/files/rs-4093653/v1/8c4a6497e7202c993c8bede8.docx"},{"id":52656947,"identity":"bfebd058-8b29-4698-b89e-ddac06fd1388","added_by":"auto","created_at":"2024-03-14 07:07:06","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":15325,"visible":true,"origin":"","legend":"","description":"","filename":"Appendix2Analysisoftheeconomicperformanceofbuildingsusingframestructures.docx","url":"https://assets-eu.researchsquare.com/files/rs-4093653/v1/75a6d19e264d09b875ea2c2a.docx"},{"id":52656954,"identity":"a1b21539-b706-47ff-a98b-44ecd00e3fa9","added_by":"auto","created_at":"2024-03-14 07:07:06","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":15413,"visible":true,"origin":"","legend":"","description":"","filename":"Appendix3Analysisoftheeconomicperformanceofthebuildingusingthetubeinthetube.docx","url":"https://assets-eu.researchsquare.com/files/rs-4093653/v1/263498a814f61a4a3f32b6c5.docx"},{"id":52656962,"identity":"0043ffb3-a6aa-4c13-9fc4-c42055b95239","added_by":"auto","created_at":"2024-03-14 07:07:07","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":14989,"visible":true,"origin":"","legend":"","description":"","filename":"Appendix4carbonemissionsperformanceanalysis.docx","url":"https://assets-eu.researchsquare.com/files/rs-4093653/v1/27bb4ea1fd834d05ffd8d414.docx"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eEffect of Biological shells aggregate on the Mechanical properties and sustainability of concrete\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003e In recent years, the treatment of garbage problem has become serious all over the world, large amount of garbage has caused serious air pollution and ecological damage, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e. In order to solve this problem, the researcher consider separating useful material from waste and using it in the research to develop new building materials. Therefore, the researchers have made relevant classification and composition screenings of the collected waste and found out that bio-shells, one of the kitchen waste, are good choice for replacing traditional concrete aggregates. As reported by previous researcher, nearly 10\u0026nbsp;million metric tons of shells of oysters, clams, scallops, and mussels are discarded globally every year.\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e Furthermore, a comprehensive survey was carried out to assess the situation of restaurants in selected provinces of China and the Republic of Belarus, the collected data revealed that the Belarusian restaurant chain brand \"Sea Food\" alone generates amounting to over 100 catties discarded seashells per day. Correspondingly, approximately 5 tons of seashells are discarded daily in the provinces Guangdong and Fujian, China.\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eTo address the pollution problem, analyzing the chemical composition and potential use of shells as building materials is very necessary. The results show that shells contain calcium carbonate, glycoprotein, proteoglycan, polysaccharide, and chitin. In the hydration process of cement, water reacts with four main clinker minerals. At room temperature, tricalcium silicate hydrates to form calcium silicate hydrate (C-S-H gel) and calcium hydroxide, while dicalcium silicate (β-C2S) hydrates to produce similar products. Tricalcium aluminate hydrates to form unstable calcium aluminate hydrate, which eventually transforms into hydrogarnet (C3AH6). The hydration reaction of iron phase solid solution (C4AF) is similar to that of tricalcium aluminate\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. By observing the hydration reaction, the researcher can conclude that shells do not affect the hydration process of cement, and thus do not cause damage to the structure and strength of concrete. Therefore, the researchers think that shells can be used as part of concrete aggregates to develop new building materials.\u003c/p\u003e \u003cp\u003eIn coastal regions, the primary source of construction sand is desalinated sea sand, which typically contains a shell content of 5%~8%. From a research of mortar, the incorporation of shells in place of river sand has a notable influence on the overall compressive strength and dry shrinkage of cement-based materials, with an increase of 8% in the proportion of shells\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. Mr. Yang has focused on studying shell aggregates as an alternative to natural aggregates. Yang's research suggests that shell aggregates hold promising potential for practical applications, offering a favorable solution to the growing shortage of natural aggregate resources. Dr. MO asserts that there is a growing inclination towards sustainability in the field of concrete engineering, primarily driven by the depletion of materials traditionally employed in the production of natural concrete. It is suggested that utilizing shell waste in the production of concrete can enhance both its workability and strength, thereby offering a viable solution\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. Kuo's experiments proposed that replacing a portion of river sand with shells in cement can lead to an increase in the proportion of shells. This substitution has had a notable impact on the overall compressive strength and shrinkage of the base material\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. Eziefula has found that shells can be used as a partial or total substitute for fine and coarse aggregates in concrete\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSome scholars in China used shells as aggregates to test concrete and found that the compressive strength of concrete increased with the raise in shell replacement rate after 28 days.\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. Sergey\u0026rsquo;s study showed that shells improved the strength, strain, modulus, and microstructure of concrete. The new concrete also reduced the cost and defects of construction. This research has practical implications.\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e. Belarus researchers tested to use agricultural waste (e.g., rice husk ash, peanut shells, oak wood chips, coconut shells, and corn cobs) as aggregate substitutes. This can lower waste pollution to environment and construction costs\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e][\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. Many studies have tested shells in concrete. From those tests, shells have more advantages over other agricultural wastes as concrete aggregates. Mart\u0026iacute;nez found that shells should not exceed 25% for fine aggregates and 12.5% for coarse aggregates to improve concrete strength\u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. Malaysian researchers have suggested that Calcined shells improve concrete strength and density. Future research should test different calcination levels and shell concrete durability. \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e In addition, according to the research of Iraqi scholars, similar to shells, crushed walnut shell is an agricultural waste material that can be used to produce environmental concrete that reduces the demand for natural aggregates and the environmental impact of concrete production\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e][\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e][\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAfter a thorough review of the above studies, our team concluded that shells possess exceptional mechanical properties\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e, a significant specific surface area, and a lower density compared to stone. As a building material, shells offer advantages such as workability, strength, and reduced weight in concrete\u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. To prepare the shells, they should be soaked in a concentrated solution of NaCl and a diluted solution of 10% H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e, after removing organism and impurities, the material is crushed and screened to produce shells with a particle size of less than 0.5mm. This not only helps save resources and energy but also reduces waste and decreases the consumption of natural aggregates\u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e][\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. As a result, it creates greater economic and social benefits\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e][\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e][\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. Additionally, the study suggests that using the right amount of shell aggregate can enhance the strength of concrete, ensuring the safety and stability of structures while promoting sustainable development\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003ePrevious studies have shown that shells have adequate strength and some superior properties as aggregates\u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. However, there is no consensus on the best way to use shells in construction, and few practical examples exist. Our team planned to test three levels of calcined shells (10%, 30%, and 50%) as aggregate replacements and compare their mechanical, economic, and environmental performance with conventional concrete.\u003c/p\u003e "},{"header":"2. Experimental program","content":"\u003cp\u003eThis experiment uses different proportions of shells as concrete aggregate, prepares cement mortar according to a certain mix ratio and curing conditions, uses different test equipment and methods to measure its compressive strength, flexural strength and water absorption rate, in order to study the effect of shell replacement of crushed stone on the performance of cement mortar.\u003c/p\u003e \u003ch2\u003e2.1 Experimental materials and proportions\u003c/h2\u003e\n\u003ch3\u003e2.1.1 The performance of the shell\u003c/h3\u003e\n\u003cp\u003eShells are the hard protective coverings of various mollusks, such as oysters, clams, mussels, and scallops. They are composed mainly of calcium carbonate, also known as limestone, which is a common ingredient of cement\u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. Shells have a complex hierarchical structure, consisting of different layers of organic and inorganic materials, arranged in various patterns and orientations. This gives them high strength and toughness, as well as resistance to fracture and damage \u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe properties of seashell concrete depend on several factors, such as the type, size, shape, and proportion of seashells, as well as the curing conditions, admixtures, and chemical treatments. Some of the effects of seashells on concrete are:\u003c/p\u003e \u003cp\u003eSetting time: Seashells can increase the setting time of concrete, due to their alkaline nature and water absorption capacity\u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e][\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e .\u003c/p\u003e \u003cp\u003eWorkability: Seashells can decrease the workability of concrete, due to their irregular shape and rough surface \u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eDensity: Seashells can increase the density of concrete, due to their higher specific gravity than cement or sand \u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e][\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eCompressive strength: Seashells can decrease the compressive strength of concrete, due to their lower bonding strength with cement paste and higher porosity 234. However, adding admixtures or applying chemical treatments can improve the compressive strength of seashell concrete\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e][\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e .\u003c/p\u003e \u003cp\u003eTensile strength: Seashells can increase the tensile strength of concrete, due to their fibrous structure and crack-bridging effect \u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e][\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFlexural strength: Seashells can increase the flexural strength of concrete, due to their higher modulus of elasticity and toughness\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eModulus of elasticity: Seashells can decrease the modulus of elasticity of concrete, due to their lower stiffness and higher deformation \u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\n\u003ch3\u003e2.1.2 Experimental materials\u003c/h3\u003e\n\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\u003eThe main component of cement %\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCaO\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSiO2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAl2O3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFe2O3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSO3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNa2O\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eK2O\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eMgO\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e64.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.37\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\u003ePhysical and mechanical properties of cement\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eStandard Consistency Water Requirement/%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSpecific surface area/\u003c/p\u003e \u003cp\u003e(m2/kg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eCoagulation time/min\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eCompressive strength/MPa\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eFlexural strength/MPa\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eInitial setting\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFinalization\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3 d\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e28 d\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3 d\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e28 d\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e360\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e175\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e235\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e27.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e49.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e8.0\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\u003eCement: P\u0026middot;O R45 cement, The main chemical composition is presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, while the physical and mechanical properties are displayed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, which complies with the requirements of EN 197-1 for chemical composition, strength, setting time, soundness, and fineness.\u003c/p\u003e \u003cp\u003eWater: ordinary tap water.\u003c/p\u003e \u003cp\u003eSand: natural river sand, in line with the construction sand standard, the bulk density is less than 1.5g/m\u003csup\u003e3\u003c/sup\u003e, the fineness modulus is 1.9, the moisture content is less than 1%.\u003c/p\u003e \u003cp\u003eStone: fine stone meets the requirements of EN 12620 for geometrical and physical properties, the bulk density is not less than 2.6g/m\u003csup\u003e3\u003c/sup\u003e, the particle size is 5mm- 7mm.\u003c/p\u003e \u003cp\u003eShell: according to the European Standards (EN \u0026minus;\u0026thinsp;12620), the aggregates used in the production of concrete are inert granular materials such as gravel, crushed stone, sand, slag, recycled concrete, and geosynthetic aggregates. The aggregates may be natural, manufactured, or recycled, hence, the substitution of shells for aggregate meets the standards. After calcination and crushing, the particle size is less than 0.5mm, the bulk density is less than 2.9g/m\u003csup\u003e3\u003c/sup\u003e, the fineness modulus is 2.9, and the moisture content is less than 1%, refer to Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e for details.\u003c/p\u003e \u003cp\u003eThe compressive strength of the concrete samples was tested at 7 days and 28 days after casting, according to EN 12390-3. The average compressive strength at 7 days was 25 MPa, 35 MPa on 28 days, which met the design requirement of 30 MPa for the structural elements.\u003c/p\u003e \u003cp\u003eThe slump test was performed on the fresh concrete mix, according to EN 12350-2. The slump value was 75 mm, which indicated a medium workability of the concrete, suitable for the casting and compaction methods used in this project.\u003c/p\u003e\n\u003ch3\u003e2.1.3 Material ratio and specimen design\u003c/h3\u003e\n\u003cp\u003eAccording to the study's conclusions and curve analysis, it is believed that as the water-binder ratio increases, the impact of coarse aggregate becomes more pronounced, resulting in lower dry shrinkage\u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e, refer Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. According to the studies of previous researchers, increasing the water-cement ratio results in higher porosity and lower strength of the concrete\u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e. After analyzing Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, and considering EU standard EN 206\u0026thinsp;+\u0026thinsp;A2 and Chinese standard GB 50010\u0026thinsp;\u0026minus;\u0026thinsp;2010, the water-cement ratio in the range of 0.45\u0026ndash;0.6 is relatively appropriate\u003csup\u003e[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e, to ensure sufficient strength and reduce porosity, it is necessary to choose a smaller water-cement ratio\u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e. So our team take a water-cement ratio of 0.5 as optimal for ensuring the strength and preventing cracking of the concrete in the experiment\u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e][\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIn this test, shells and other materials were used as a substitute for natural stone. The mix ratio (kg/m3) of the cement mortar in the benchmark group was as follows: m (cement): m (sand): m (stone): m (water)\u0026thinsp;=\u0026thinsp;500: 600: 900: 250, the mix ratio (kg/m3) of the cement mortar in the 10% shell replacement rate was as follows: m (cement): m (sand): m (stone) : m(shell): m (water)\u0026thinsp;=\u0026thinsp;500: 600: 810:90: 250, the mix ratio (kg/m3) of the cement mortar in the 30% shell replacement rate was as follows: m (cement): m (sand): m (stone) : m(shell): m (water)\u0026thinsp;=\u0026thinsp;500: 600: 530: 270: 250, the mix ratio (kg/m3) of the cement mortar in the 50% shell replacement rate was as follows: m (cement): m (sand): m (stone) : m(shell): m (water)\u0026thinsp;=\u0026thinsp;500: 600: 450: 450: 250. All the mixes conform to standard EN 206-1, the mixture is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. Additionally, the superplasticizer content was 0.2% of the cement mass. The gravel is replaced based on shell gradients of 10%, 30%, and 50%. The mixture was evenly stirred and poured into a mold with dimensions of 400 mm\u0026times;400 mm\u0026times;1600 mm, the test prisms is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, followed standard EN 12390-5:2009. Thirteen specimens are cast for each different gradients, 39 specimens in total for bending experiments. The specimens for compressive experiments are 100 mm\u0026times;100 mm\u0026times;100 mm, followed the standard EN 12390-3:2019, with 13 specimens cast at the each gradient, 39 specimens in all. After segmental vibration compaction, the specimens were hardened at 23\u0026deg;C, demoulded after 7 days, and cured at 20\u0026deg;C with a relative humidity of 95% until the specified age\u003csup\u003e[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\n\u003ch3\u003e2.1.4 Experimental procedure\u003c/h3\u003e\n\u003cp\u003eAfter curing for 28 days, the specimen underwent test using the DS2-1000N compressive strength tester for axial compressive resistance and three-point bending. The \"Hydraulic Pressure Testing Machine-GB/T3722\" was used to conduct a uniaxial compressive test on the specimen, aligning the axis with the pressure center of the testing machine's pressure plate. The load was applied at a speed of 10 kN/s to 30 kN/s until the specimen failed, and the failure load was recorded to determine the compressive and flexural strengths\u003csup\u003e[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/sup\u003e. The test block was soaked in water for 2 days, taken out to dry completely, recorded the weight before and after. The water absorption rate was calculated to evaluate the frost resistance strength.\u003c/p\u003e "},{"header":"3. Experimental results and analysis","content":"\u003cp\u003e3.1 Flexural strength\u003c/p\u003e\u003cp\u003eThe failure load of the specimen was obtained through a three-point bending test, testing followed the third point loading because it is simpler to perform and analyze than the fourth point loading\u003csup\u003e[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]\u003c/sup\u003e. The testing were following the standard ASTM C78/C78M and the flexural strength is presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, and the flexural strength ff (MPa) of the specimen is calculated according to the formula \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\varvec{f}}_{\\varvec{f}}=\\frac{\\varvec{F}\\varvec{l}}{\\varvec{b}{\\varvec{h}}^{2}}\\)\u003c/span\u003e\u003c/span\u003e, the testing is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, where ff is the concrete flexural strength (MPa), F is the failure load of the specimen (N), L is the span between the supports (mm), and b is the cross-sectional width of the specimen (mm), h is the cross-sectional height of the specimen (mm); the scatter plot distribution of flexural strength is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\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\u003eConcrete flexural strength under different substitution rates\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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 \u003cdiv align=\"left\" 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=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eShell replacement rate/%.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"6\" nameend=\"c7\" namest=\"c2\"\u003e \u003cp\u003eFlexural strength f\u003csub\u003ef\u003c/sub\u003e (MPa).\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0 (Standard Group)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e10.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e3.2 Compressive strength\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThrough the uniaxial compressive test, the uniaxial compressive failure load of the specimen is determined, and the compressive strength fc(MPa) of the test cube can be calculated according to the formula\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\varvec{f}}_{\\varvec{c}}=\\varvec{F}/\\varvec{A}\\)\u003c/span\u003e\u003c/span\u003e, here fc is the compressive strength, F is the failure load, and A is the bearing area. Intensity data is presented in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The scatter plot distribution of compressive strength is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e. The damage situation is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\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\u003eCompressive strength of concrete under different replacement rates\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" 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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eShell replacement ratio/%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"6\" nameend=\"c7\" namest=\"c2\"\u003e \u003cp\u003eCompressive strength fc (MPa).\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0 (Standard Group)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e20.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e19.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e20.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e20.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e18.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e23.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e21.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e22.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e22.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e21.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e22.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e22.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e22.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e20.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e22.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e22.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e21.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e22.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e23.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e22.9\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 \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e3.3 Microstructure analysis\u003c/p\u003e \u003cp\u003eIn order to carry out a more comprehensive analysis of the impact of shell aggregates on the mechanical properties of concrete at a microscopic level, the researcher performed scanning electron microscopy (SEM) on shell aggregates with varying replacement rates (0%, 10%, 30%, and 50%). This allowed us to observe the surface structure of the concrete under different shell replacement conditions. Figure\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003ea depicts concrete without shell aggregate, Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003eb illustrates concrete with a 10% shell aggregate. In Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003ec, concrete with a 30% shell aggregate is shown, and Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003ed displays concrete with a 50% shell replacement rate. By comparing these four sets of images, it is evident that the inclusion of shell aggregate in concrete enhances the compactness of the joints between concrete structures, resulting in improved stress performance and a reduced risk of compressive cracking. Consequently, the overall working performance of the concrete is enhanced.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e3.4 Waters absorption ratio\u003c/p\u003e \u003cp\u003eAfter measuring the mass of the samples before and after, the water absorption rate can be calculated by formula \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varvec{W}=(\\varvec{B}-\\varvec{G})/\\varvec{G}\\times 100\\varvec{\\%}\\)\u003c/span\u003e\u003c/span\u003e, G is the weight of the sample after drying, B is the weight of the sample saturated with water, the testing method was according to the EN 12390-8:2009, and the data is presented in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The curve depicting the change in water absorption is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\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\u003eConcrete moisture content under different substitution rates\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=\"char\" char=\".\" 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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eShell replacement ratio/%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWeight before tumbling/g\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWeight after drying/g\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWater absorption/%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0 (Standard Group)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e634.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e614.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e607.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e576.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e609.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e582.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e601.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e573.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e "},{"header":"4. Prediction of the mechanical strengths","content":"\u003cp\u003eBased on the analysis of the data obtained from the three-point flexural test (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), the researcher get the following conclusions: when the shell replacement rate is 10%, the flexural strength of the specimen increases by 31.4% and 1.925MPa compared to the benchmark group. When the shell replacement rate is 30%, the flexural strength of the specimen increases by 52.4% and 3.208MPa compared to the benchmark group. The flexural strength of the specimen increases by 64.6% and 3.958MPa respectively when the shell replacement rate is 50%. According to the mechanical curve shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e, it is evident that the addition of the shell significantly enhances the flexural strength of the prism when compared to traditional aggregate. This indicates that the inclusion of shell aggregate reduces the concrete's susceptibility to bending and fracturing. Consistent with the experimental phenomenon, previous research has shown that the addition of shells improves post-cracking behavior, reduces the opening of cracks, and counteracts their expansion, as well as increases the toughness of concrete owing to their deboning and internal stresses mechanisms\u003csup\u003e[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e][\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e. Furthermore, due to the adsorption capacity of shells \u003csup\u003e[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e,when the shell is aligned with the tensile direction, it is capable of bearing the tensile force and impeding crack propagation\u003csup\u003e[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/sup\u003e. Therefore, the shells with higher content have a wider and more uniform distribution in the concrete, as the cement does not have a significant effect on the shells during the hydration process, and no settlement or floating occurs, which also improves the tensile strength of the concrete. These findings are supported by the available data, when the shell replacement rates were 10%, 20%, and 30% respectively, the mixing ratio increased by 10% each time, and the 90 d tensile strength of the concrete with traditional aggregate increased by 11.8%, 15.1%, and 17.6% respectively.\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e][\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e][\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e][\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn the uniaxial compressive test (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), it was observed that the compressive strength of the specimen increased by 10.7% and 2.727MPa when the shell replacement rate was 10% compared to the benchmark group. Similarly, when the shell replacement rate was 30%, the compressive strength of the specimen increased by 16.6% and 3.207MPa compared to the benchmark group. The compressive strength of the specimen increased by 17.8% and 3.442MPa compared to the benchmark group when the shell replacement rate was 50%.\u003c/p\u003e \u003cp\u003eWith check of the curve depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e, it is evident that the inclusion of shell aggregates leads to a significant enhancement in compressive strength. This observation suggests that the addition of shell aggregates improves the concrete's resistance to compression-induced damage and enhances its load-bearing capacity. Upon comparing the curves depicted in Figs.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e and \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e, it is evident that the curve exhibits a rapid raise in the range of 0\u0026ndash;30% replacement rate. However, the rate of increase slows down between 30% and 50%, and eventually reaches a plateau when it approaches 50%. This observation suggests that shells can be substituted at a rate as high as 50% while still providing satisfactory strength as aggregates.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e presents scanning electron microscope (SEM) images of shell concrete at a 28-day scale, depicting various shell aggregates with distinct gradients in intensity. Based on the captured images of moral onlookers, the researcher conducted a further analysis on the impact of shell aggregates on the mechanical properties of natural aggregates. Based on the SEM microscopic diagram of the failed samples, it can be observed that the cracking in the shell aggregate concrete with 0% content is more pronounced and the spacing between cracks is larger. In contrast, the shell aggregate concrete with 10% content exhibits significantly smaller fracture spacing compared to the 0% content. Moreover, the shell aggregate concrete with 30% and 50% content only shows a limited number of microcracks and pores, which can be considered the mechanically weak areas. Hence, it has been demonstrated that incorporating crushed shells into concrete under identical pressure conditions can effectively enhance the mechanical properties of the concrete. Further examination of Figs.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003eb, c, and d reveals that the concrete structure exhibits a high level of compactness, with no presence of a cementitious porous structure. This observation effectively demonstrates the favorable workability of the concrete material when shell aggregate is added as a composite material. Additionally, the shell aggregate is capable of forming a dense matrix structure with the natural aggregate, resulting in strong compactness and low porosity. This further enhances the bonding between the cement slurry and the aggregate matrix. Therefore, the incorporation of shell aggregate as a partial replacement for natural aggregate has been found to significantly enhance the mechanical properties of concrete.\u003c/p\u003e \u003cp\u003eCong proposed that there was a positive correlation between the moisture content of concrete and its higher frost resistance\u003csup\u003e[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/sup\u003e. Therefore, it is hypothesized that the frost resistance of the test block may be influenced by its water absorption capacity, it can be considered that the lower water absorption rate, the more favorable frost resistance of the material\u003csup\u003e[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]\u003c/sup\u003e. It is expected that a lower water absorption rate would result in a lower moisture content within the test block, thereby enhancing its frost resistance\u003csup\u003e[\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]\u003c/sup\u003e. Based on the analysis of the curves presented in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, it can be inferred that the replacement of traditional aggregate with shell leads to a slight increase in the moisture content of the test block. Consequently, it can be concluded that the frost resistance of the shell aggregate is poor. With the gradual increase in the replacement rate of aggregate, there is minimal fluctuation in the moisture content. It can be inferred that while the replacement rate of shell aggregate may decrease the frost resistance, varying replacement rates have a negligible impact on the frost resistance of concrete.\u003c/p\u003e \u003cp\u003eFurthermore, in the process of experiment, it was observed that the application of mechanical vibration in the concrete exhibited a flow-like behavior, allowing it to evenly and densely fill the formwork. The destruction section displayed a uniform distribution of shells, with no instances of delamination or segregation. Additionally, it was noted that there were no significant issues with water leakage during the curing process. It can be inferred that the use of shells as aggregates exhibits favorable workability and integrity.\u003c/p\u003e "},{"header":"5. Life cycle assessment","content":"\u003cp\u003e5.1 Economical assessment\u003c/p\u003e \u003cp\u003eThe researchers believe that in the process of studying the replacement of traditional aggregates by shells, in order to explore the application of aggregates in actual production, it is very important to analyze its economic performance. Take the China Construction Project Budget Quota to calculate the cost of concrete: 180 yuan//m\u003csup\u003e3\u003c/sup\u003e for sand, 4.1 yuan/m\u003csup\u003e3\u003c/sup\u003e for commercial water, 635 yuan/ton for cement, 220 yuan/m\u003csup\u003e3\u003c/sup\u003e for stone, one cubic meter of concrete weighs 2400 kg. The cost of commercial concrete is 635 yuan/m\u003csup\u003e3[\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]\u003c/sup\u003e. In addition, the researchers investigated the garbage recycling plant and recycled the waste shells, found that the waste shells were biological waste, and the recycling plant believes that they do not have recycling value, so they can be obtained free of charge, and only need to issue relevant labor costs, and the cost of shells can be calculated according to the labor cost of 10 yuan per m\u0026sup3;\u003csup\u003e[\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e5.1.1 Economic performance analysis of buildings using frame shear structure\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe researchers take a significant high-rise building project covering a total area of 173,256.37 m\u003csup\u003e2\u003c/sup\u003e in East of China as a sample. The structure of the building is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e. To assess the economic viability of shell aggregates, the researcher substituted all concrete materials with 50% shell aggregate concrete. Upon comparison with traditional aggregates, it was found that the total concrete consumption amounted to 82,226.37 m\u003csup\u003e3\u003c/sup\u003e. Full analysis details are given in Appendix 1.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e5.1.2 Analysis of the economic performance of buildings using frame structures\u003c/h2\u003e \u003cp\u003eThe researchers take a nine-storey frame structure in southern China as a sample, with a total area of 12055.52 m\u003csup\u003e2\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig16\" class=\"InternalRef\"\u003e16\u003c/span\u003e), to assess the economic performance of shell aggregates. An analysis was carried out by replacing all concrete with 50% shell aggregate concrete compared to traditional aggregates. The total concrete consumption for this structure amounted to 3389.92m\u003csup\u003e3\u003c/sup\u003e. Full analysis details are given in Appendix 2.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e5.1.3 Analysis of the economic performance of the building using the tube in the tube\u003c/h2\u003e \u003cp\u003eThe researchers take a building with a tube structure in southern China as a sample, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e17\u003c/span\u003e, which has a total area of 341376.54 m\u003csup\u003e2\u003c/sup\u003e. To evaluate the economic performance of shell aggregate, an analysis is base on replacing all concrete with 50% shell aggregate concrete. The total volume of concrete used in this structure was 263,124.38 m\u003csup\u003e3\u003c/sup\u003e. Full analysis details are given in Appendix 3.\u003c/p\u003e\u003cp\u003eCompare the cost of replacing traditional aggregates with shells in three building structures (Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e18\u003c/span\u003e), the researchers calculated that the concrete costs of the frame-shear structure, frame structure, and tube-in-tube structure are reduced by 10.2%, 10%, and 10.3% respectively. This suggests that shells aggregate can effectively reduce building costs.\u003c/p\u003e \u003cp\u003e5.2 Environmental assessment\u003c/p\u003e \u003cp\u003eIn order to assess the environmental impact of shell aggregates, it is important to consider carbon emissions. This includes the carbon emissions from the production of raw materials (C\u003csub\u003e1a\u003c/sub\u003e), which refers to the CO\u003csub\u003e2\u003c/sub\u003e generated during the production and processing of raw materials. This includes energy consumption and carbon emissions from the material processing itself. The calculation formula for C\u003csub\u003e1a\u003c/sub\u003e is as follows:\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\varvec{C}}_{1\\varvec{a}}=\\sum _{\\varvec{i}}\\left(\\sum _{\\varvec{j}}{\\varvec{a}}_{\\varvec{i}\\varvec{j}}{\\varvec{K}}_{\\varvec{j}}\\right){\\varvec{m}}_{\\varvec{j}}+{\\varvec{g}}_{1}{\\varvec{m}}_{1}\\)\u003c/span\u003e\u003c/span\u003e. In the formula, a\u003csub\u003eij\u003c/sub\u003e represents the energy consumption of class j in the production process of class i raw materials. m\u003csub\u003ej\u003c/sub\u003e represents the amount of class I raw materials used in 1 m\u003csup\u003e3\u003c/sup\u003e of recycled concrete. k\u003csub\u003ej\u003c/sub\u003e is the carbon emission coefficient of class J energy, which is the sum of the direct carbon emission coefficient Kj and the indirect carbon emission coefficient K\u003csub\u003ej\u003c/sub\u003e. g\u003csub\u003e1\u003c/sub\u003e represents the carbon emission generated by the material itself in the process of cement production, m\u003csub\u003e1\u003c/sub\u003e represents the amount of cement in 1 m\u003csup\u003e3\u003c/sup\u003e of recycled concrete \u003csup\u003e[\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]\u003c/sup\u003e. The study will utilize the mixture ratio of experimental test blocks to calculate parameters for carbon emissions. The calculation parameters for carbon emissions are presented in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, while Table\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e displays the carbon emissions resulting from energy consumption. Full analysis details are given in Appendix 4.\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\u003eCarbon emission calculation parameters\u003csup\u003e[\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e][\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]\u003c/sup\u003e\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=\"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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnit material\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePower Consumption/\u003c/p\u003e \u003cp\u003e(kW\u0026middot;h)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCoal Consumption/\u003c/p\u003e \u003cp\u003eKg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDiesel Consumption/\u003c/p\u003e \u003cp\u003eL\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1t cement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e96\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\u003e1t natural coarse aggregate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.723\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1t sand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1t water\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\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=\"Tab7\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCarbon emissions generated by energy /kg\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=\"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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnit energy\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDirect carbon emissions\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIndirect carbon emissions\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTotal carbon emissions\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1kW h of electrical energy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.195\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.195\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1kg of coal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.088\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.618\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1L diesel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.448\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.178\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\u003eThe carbon emission curve of concrete at different shell replacement rates suggests that incorporating shells, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e19\u003c/span\u003e, can effectively reduce carbon emissions. This reduces energy consumption and minimizes the environmental impact of buildings, protecting the ecological environment\u003csup\u003e[\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe researchers tested mechanical properties of the concrete specimens with 10%, 30% and 50% crushed bio-shell as a replacement aggregate, calculated the concrete cost of three different types of building, and evaluated carbon environmental impact of the specimens using a carbon environmental protection formula. The main conclusions are summarized below:\u003c/p\u003e\n\u003cp\u003e(1) The substitution rate of shell can reach up to 50%, and the higher the substitution rate within this range, the greater the enhancement in concrete strength. The maximum increase in flexural strength can reach 3.96 MPa, and the highest increase in compressive strength can reach 2.5 MPa.\u003c/p\u003e\n\u003cp\u003e(2) After calculating the project\u0026apos;s actual content, it was found that using shell aggregate concrete can reduce material costs by approximately 10% for various structural projects. This significantly addresses the issue of excessive project costs.\u003c/p\u003e\n\u003cp\u003e(3) Based on a carbon environmental protection formula, we find that shell aggregate exhibits commendable environmental performance. In addition, This approach effectively mitigates kitchen waste disposal, reduces energy consumption, minimizes the environmental impact of carbon dioxide emissions, enhances the ecological environment, and ultimately yields significant social benefits.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eXianpeng Wang\u003csup\u003e1\u003c/sup\u003e\u003csup\u003e＊\u003c/sup\u003e: experiment, investigation, data management, methodology, formal analysis, conceptualization, writing-original draft, project administration.\u003c/p\u003e\n\u003cp\u003eHaoxuan Yu\u003csup\u003e1\u003c/sup\u003e\u003csup\u003e＊\u003c/sup\u003e: experimentation, investigation, data validation, writing, review and editing.\u003c/p\u003e\n\u003cp\u003eFulong Li : Professor Li \u0026nbsp; helped with the revision comments of the peer reviewers, reviewed the final version, and provided a lot of support for subsequent research materials.\u003c/p\u003e\n\u003cp\u003eKovshar Sergey Nikolayevich\u003csup\u003e1\u003c/sup\u003e: provide experimental materials, provide experimental help, review the final manuscript and edit comments, and supervise the entire experimental process.\u003c/p\u003e\n\u003cp\u003eHaojue Yu\u003csup\u003e1\u003c/sup\u003e,My colleague Yu Haojue has excellent English proficiency and has rigorously proofread the English grammar and civil engineering English vocabulary of the full text.\u003c/p\u003e\n\u003cp\u003eLeonovich Sergey Nikolaevich\u003csup\u003e1\u003c/sup\u003e\u003csup\u003e*\u003c/sup\u003e: review, comment and edit, supervise, and verify data.\u003c/p\u003e\n\u003cp\u003eWenbing F:He made detailed revisions to the abstract and conclusion sections and provided great help in solving the reviewers\u0026apos; questions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData will be made available on request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe first corresponding author, Ph.D student Xianpeng Wang, thanked the China Scholarship Council for the self-help in life.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eМария Немцева (2019) 9, 16). 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Sci Rep 14:136. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41598-023-47933-9\u003c/span\u003e\u003cspan address=\"10.1038/s41598-023-47933-9\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[{"identity":"f652b943-b236-4cd1-a6f3-0baa36693b2d","identifier":"10.13039/501100005195","name":"China University of Mining and Technology","awardNumber":"no","order_by":0}],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"Belarusian National Technical University","isAcceptedByJournal":true,"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":"aggregate concrete, shell aggregate, mechanical properties, carbon emission, economic analysis","lastPublishedDoi":"10.21203/rs.3.rs-4093653/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4093653/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTo solve waste bio-shell and put them into recycle, the researchers proposed using waste bio-shells as aggregate matrix for concrete. In order to determine the substitution amount of shells, the researchers used the orthogonal experimental method, and designed shell concrete experiments with gradient substitution rates at 10%, 30% and 50%, with a total of 78 groups of specimens. By analyzing the tensile, bending and frost resistance of these specimens, the experimental data show that adding shells as aggregate at 10%, 30% or 50% can improve the mechanical properties of the concrete, the maximum flexural strength can be increased by 3.96Mpa, the maximum compressive strength can be increased by 2.5Mpa, but with a degradation of frost resistance. With the investigate of economic performance, it was found that the costs of frame-shear structure, frame structure, and tube-in-tube structure were reduced by 10.2%, 10%, and 10.3% respectively. In the carbon environmental assessment, the carbon reduction of a single specimen with 10%, 30%, and 50% shell addition were 0.003, 0.0010, and 0.0015 kg respectively. In summary, compared with ordinary concrete materials, it is very possible to use waste bio-shells as a substitute for aggregates to develop the sustainable recycling development of concrete materials.\u003c/p\u003e","manuscriptTitle":"Effect of Biological shells aggregate on the Mechanical properties and sustainability of concrete","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-14 07:07:01","doi":"10.21203/rs.3.rs-4093653/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":"9eeeaab3-f732-4450-ae41-8fc191d7b7fa","owner":[],"postedDate":"March 14th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-05-12T07:03:10+00:00","versionOfRecord":{"articleIdentity":"rs-4093653","link":"https://doi.org/10.1038/s41598-024-61301-1","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2024-05-09 07:03:10","publishedOnDateReadable":"May 9th, 2024"},"versionCreatedAt":"2024-03-14 07:07:01","video":"","vorDoi":"10.1038/s41598-024-61301-1","vorDoiUrl":"https://doi.org/10.1038/s41598-024-61301-1","workflowStages":[]},"version":"v1","identity":"rs-4093653","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4093653","identity":"rs-4093653","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}