Moreover, combined with the four-point flexural test of the SFRC components post fire, the research also describes the damage of high temperatures to the flexural toughness of SFRC components, and suggests a calculation formula for SFRC thermal conductivity by way of the numerical inversion method. The results of this study have verified that the incorporation of steel fiber into concrete helps to reduce its internal thermal stress difference and improve the crack resistance and fire resistance of the concrete. Moreover, under high temperature conditions, the concrete component added with the steel fiber in an aspect ratio of 70 and a dosage of 45 kg/m3 increased their initial crack flexural strength by 56.8%, higher than that of plain concrete components, and the loss of equivalent flexural strength and flexural toughness of SFRC post fire was only 45.2% and 13.6%, respectively. The proposed calculation formula of thermal conductivity can provide a reference for a numerical simulation study of the temperature field of SFRC components in a high temperature environment.Steel fibers are widely used because they can effectively improve the tensile, compressive and flexural properties of concrete structures. The selection of steel fiber dosage and aspect ratio at high temperature has an important impact on the flexural toughness of concrete components post-fire. In this paper, discussions are made on the simulated fire test in compliance with the ISO 834 standard to study the steel fiber-reinforced concrete (SFRC) components post-fire. The research reveals the influence of two commonly used steel fiber aspect ratios  and steel fiber dosages (30 kg/m The deviation calculation result was within the specification limit, indicating that the temperature control in the entire combustion heating test furnace met the requirements, the high temperature scene simulated by the test was in line with the actual high temperature situation and subsequent evaluation analysis could be carried out on the specimens under high temperature working conditions.The actual heating curve and the standard heating curve of each time period and the area enclosed by the time axis were obtained; thus, the area deviation of each section in After ignition, the temperature in the furnace increased rapidly, and the temperature inside the specimens in four steel fiber dosages and in different distance as of 10, 20, 30, 50, 80, and 120 mm from the fire surface is shown in II-45 > TBII-40 > TBII-30 > TBII-0. This is because the thermal conductivity of steel fibers is stronger than that of concrete, so as the amount of steel fibers increases, the temperature in the specimens increases. Given the limited burning time and the comparatively longer distance from the fire surface, the data after 110 °C were selected for analysis only to avoid the influence of the temperature platform on the specimens. The internal temperatures of the specimens shown at 80 mm and 120 mm distances from the fire surface did not exceed 110 °C in the fire test, so they were excluded from the in-depth analysis. It can be seen from II-45, TBII-40 and TBII-30 were 23.5%, 11.3% and 1.8% higher than those of TBII-0, respectively. The results show that the incorporation of steel fibers into concrete can help cut down the temperature gradient inside the concrete, reduce the thermal stress difference caused by the temperature difference and inhibit the generation and development of small cracks in the specimen, thereby improving the crack resistance and fire resistance of the concrete.3. This was because the specimen had the lowest dosage, a shorter aspect ratio and a weaker adhesion than the other specimens. As no similar spalling was found on other specimens, it might be suggested that the mixing and stirring were not fully or evenly conducted when the steel fibers were added in the questioned specimen.The specimens subjected to high temperatures by fire are shown in ef. This standard evaluation method is not affected by the position of the initial crack point. The initial crack point is the point at which the load–deflection curve changes from linear to nonlinear. For the deficiencies of the JSCE-SF4 standard [eR, which is a dimensionless value, thus solving the problem in comparative analysis of specimens in different sizes. Therefore, the CECS 13:2009 standard [ef, the flexural toughness ratio eR and the initial fracture strength crf of fiber reinforced concrete (Formulas (3)–(5) [ef is the equivalent flexural strength (MPa); kΩ is the area under load–deflection curve with mid-span deflection L/150; L is the span between test beam supports (mm); b is the specimen section width (mm); h is the specimen section height (mm); kδ is the deflection value of the mid-span deflection is L/150; eR is the flexural toughness ratio; crf is the initial fracture strength of fiber-reinforced concrete (MPa); crF is the initial crack flexural strength of fiber-reinforced concrete (N).There are many evaluation methods for the flexural toughness of concrete members in the world, such as the ASTM C1018 standard  in the Ustandard , the CECstandard  proposesstandard  was used (3)–(5) ).(3)fe=kΩ curve was obtained using the origin software. The span L between the test supports was 300 mm. The area under the 3, the SFRC had the best flexural performance. It can also be seen from According to the load–deflection curve, and Formula (3) to Formula (5) , the equ3 was almost 100%. Compared with other steel fiber types and dosages, the minimum damage of Type II at a dosage of 45 kg/m3 was 45.2%. The equivalent flexural strength of Type I at a dosage of 45 kg/m3 was 1.5 times that of Type I at a dosage of 40 kg/m3; the equivalent flexural strength of Type II at a dosage of 45 kg/m3 was 1.4 and 2.4 times that of Type II in dosages of 40 kg/m3 and 30 kg/m3, respectively. At the same dosage, the equivalent flexural strength of Type II was higher than that of Type I, among which, that of the steel fiber specimen at a dosage of 45 kg/m3 increased by 52.9%. The maximum equivalent flexural strength of Type II at a dosage of 45 kg/m3 was 8.68 MPa, which was 1.1 and 1.3 times that in 40 kg/m3 and 30 kg/m3, increasing by 17.8% compared with SFRC Type I in the same dosage.3 was adopted, and the improving of the flexural toughness ratio of steel fiber Type I was significantly less than that of Type II. Under high temperature conditions, the flexural toughness ratio of Type II in dosage of 45 kg/m3 was 1.5 times that of Type I in the same dosage, only reduced by 13.3% compared with that under normal temperature conditions. That damage reduction value was the minimum damage value of the flexural toughness ratio among all steel fiber dosages and types.Under both working conditions, the flexural toughness ratio of SFRC reached the maximum value when steel fiber Type II in dosage of 45 kg/m(1)the temperature field analysis involved here was an uncoupled heat transfer analysis, so the stress and strain had no effect on the temperature field of the model;(2)the heat released by the SFRC specimens during the heating process due to a series of internal chemical reactions was ignored;(3)the heat loss due to the evaporation of pore water inside the SFRC specimens during the heating process was not considered;(4)it was assumed that the concrete and steel fibers were isotropic, and all isotropic thermal parameters were the same value;(5)except for the surface that was in direct contact with the open flame, the rest sides of the specimens werethermal insulation surfaces.According to the principles of heat transfer, there are three basic ways of heat transfer: heat conduction, heat convection and heat radiation . The theρ is the material density (kg/m3); C is the specific heat of the material (J/(kg·K)); λ is the thermal conductivity of the material (W/(m·K)); T is the temperature of the material at any time (°C); g is the heat generated per unit volume of the material in per unit time (W/m3).In calculating the temperature field of concrete components, the heat conduction is a nonlinear transient issue because the thermal conductivity and specific heat of concrete are not constant. The concrete heat conduction differential formula is a nonlinear parabolic partial differential formula. The basic differential formula for the transient heat conduction of concrete is Formula (6) :(6)ρC∂T∂g is taken as 0. Therefore, the three-dimensional temperature field issue of the above formula can be simplified to a two-dimensional temperature field issue along the section [ρc is the density of concrete (kg/m3); Cc is the specific heat of concrete (J/(kg·K)); λc is the thermal conductivity of concrete (W/(m·K)).It is generally agreed that in the calculation of the temperature field of the concrete beam, the temperature along the longitudinal direction of the concrete beam is the same, and there is no heat source inside the component, that is,  section , and the section :(7)ρcCc∂λc, Cc, and ρc, among which, λc varies greatly due to different concrete types, and is believed in negative correlation with temperature T [λc in the Eurocode were referred to for calculation, which is Formula (8), and Cc as to Formula (10). The thermal conductivity λs and specific heat Cs of steel fibers were the same as those of ordinary steel. Referring to the calculation formula of the European Code for Design of Steel Structures [λs and Cs were (11) and (12), respectively.The main thermal parameters involved in the above Formula (7) are: rature T . The exirature T ,65,66. Crature T ,67. The rature T ,67. So, ructures , the calThe upper limit of the thermal conductivity of concrete:The lower limit of the thermal conductivity of concrete:The specific heat of concrete:The thermal conductivity of steel fiber:Cs is specific heat for steel fibers (J/(kg·K)); λs is the thermal conductivity of steel fibers (W/(m·K)); T is the temperature of the material at any time (°C).The specific heat of steel fiber:3. The steel fiber was established with the optimum dosage of 45 kg/m3 of Type II, its thermal conductivity and specific heat were calculated according to Formulas (11) and (12), and the steel fiber density was set at 7800 kg/m3. It is worth noting that the steel fiber model was established without considering the geometry. In other words, straight and flat steel fibers with a circular cross-section were used in the numerical simulation. According to the amount of steel fibers, 1417 fibers were generated and assembled randomly and uniformly in the concrete model, as shown in Concrete and steel fibers were set up independently in the ABAQUS model, and their material properties of concrete and steel fibers needed to be investigated separately. The concrete size was established according to the test prototype, which was 150 × 150 × 300 mm. The concrete was established according to the test prototype, its thermal conductivity and specific heat were calculated according to Formulas (8) and (10), and concrete density took a constant value of 2400 kg/m−8 W/(m2·K4) [In the numerical analysis, the analysis step was set to transient heat transfer, the duration time of single-side fire was 60 min and the ambient temperature at the start of the modeling was the same as the temperature in the furnace before the test, which was 15 °C. Except the fire surface, the other surfaces of SFRC specimens were covered with refractory cotton for thermal insulation, so they were regarded as thermal insulation surfaces. The absolute zero degree was fixed as −273 °C, and the Stefan-Boltzmann constant was 5.67 × 10/(m2·K4) , which w/(m2·K4) , the conThe cloud diagram of the calculated temperature field is shown in It can be seen from Cc and density ρ of concrete remained unchanged, the λSFRC Formula (13) was put forward here based on Formula (8), so that the temperature–time curve calculated by the simulation was more consistent with the test values.Upon the comparison of the temperature field between the above test values and the simulated values, it was clear that there was a certain deviation between the temperature conditions calculated by using the upper limit of the thermal parameters of the Eurocode and the test values. That upper limit was too conservative. The research of Kodur et al.  showed tλc and λSFRC when exposed to fire for 60 min.According to Formula (13), the SFRC temperature field was calculated, verified and compared with the test values, the temperature–time curves at different distances from the fire surface thus obtained are shown in λSFRC was closer to the test values, and the temperature difference from the test data when exposed to fire for 60 min changes greatly compared with the λc simulation. Combining with λSFRC was closer to the test values, which proves that λSFRC is more suitable for the calculation of the temperature field of SFRC structure.Comparing (1)Incorporation of steel fibers into concrete helps decrease the temperature gradient inside the concrete, reduce the internal thermal stress difference and improve the crack resistance and fire resistance of the concrete;(2)Compared with each SFRC specimen, the plain concrete specimen had a higher damage value of the initial crack flexural strength, which indicates that the addition of steel fibers helps reduce the high temperature impact on the degree of damage to the initial crack flexural strength of concrete;(3)Steel fibers can significantly improve the equivalent flexural strength of concrete under both normal and high temperature conditions. Moreover, in the scope of this study, the equivalent flexural strength increased with the increase in steel fiber dosages;(4)SFRC was more similar to the test values than that of λc, which verifies the rationality of formula λSFRC.The simulated temperature value of λBased on the ISO 834 standard heating curve, an open flame test was carried out on SFRC, and the distribution law of the internal temperature field of the SFRC structure under single-side fire was studied. Through the tests on the standard flexural toughness of the concrete specimens in different steel fiber types and dosages, the damage degree of equivalent flexural strength and flexural toughness of SFRC was ascertained compared with plain concrete. The temperature field of SFRC under standard fire environment was simulated and analyzed by using ABAQUS numerical simulation software, and a calculation formula of thermal conductivity of SFRC was proposed. The main conclusions are as follows:


Reclaimed Asphalt Pavement (RAP) as recycled aggregates is a relatively new construction process of rigid pavements due to the scarcity and degradation of natural aggregates. This study aims at the sequential characterization of RAP aggregate to obtain optimized proportions for strength. For this purpose, RAP aggregates were used for the replacement of natural aggregates (NA) in the concrete mix which was achieved by varying from 0–100%. Furthermore, zirconia silica fume (ZSF) was used as a partial replacement of the cement in the concrete mix, replacing Ordinary Portland Cement (OPC). Experimental studies have shown that the incorporation of washed RAP (WRAP) slightly reduces the compressive strength of concrete by 2.7–37.35% as compared to the reference control concrete mix. Although the 7-days, 28-days and 56-day compressive strength of WRAP recycled aggregate-based concrete is slightly better than the 7-days, 28-days and 56-day compressive strength of dirty RAP (DRAP) recycled aggregate-based concrete. A similar trend was observed in the flexural strength and split tensile strength of WRAP recycled aggregate-based. Overall, the results show that 40% WRAP recycled aggregates with 10% ZSF as a replacement for cement outperform DRAP aggregates in concrete mixes. According to the ANOVA results, the combination of ZSF and WRAP aggregates met the cement concrete pavement strength standard, thereby contributing to sustainable development. Reclaimed Asphalt Concrete Pavements (RACP) are now seen as a potential and long-term answer to the present environmental and economic crisis. Due to the depletion of limited sources of natural aggregates (NA), there is a scarcity in the global market leading to a surge in the cost of NA. One of the best alternative sustainable approaches is to utilize recycled aggregates in road construction ,2,3. Mos2 is released per ton of cement produced, which amounts to 7–9% of total carbon dioxide emissions [RAP is the residue material collected from the asphalt pavement by the ripping and crushing process ,12,13. Fmissions . So, recmissions ,19,20. Rmissions ,22,23. Bmissions  studied missions  cleared missions . In ordemissions . For themissions ,29,30. Mmissions . Similarmissions ,32,33. Tmissions ,36,37,38missions . The utimissions ,41. Hencmissions . So, sevmissions ,45,46,47missions  validatemissions  found thmissions  indicateTherefore, efforts have been made to properly characterize collected RAP materials from different sources of local sites. In this current study, we develop the strength and potential of RAP aggregates by removing dust, agglomeration, and coated asphalt. The literature that is now available claims the inclusion of RAP degrades the concrete characteristics but nonetheless appears to be an innovative way to partially substitute virgin aggregates. Likewise, this article also addressed the inclusion of locally accessible materials, which will aid in the construction of sustainable rigid pavement and a greener environment.Most of the literature pertaining to RAP recycled aggregates in cement concrete mixes has either determined the optimal proportions of RAP based on strength criteria or characterized the RAP based on physical and chemical properties. There is limited research that addresses the properties of RAP recycled aggregates as well as the optimal proportions of RAP used in concrete mixes. Consequently, an attempt has been made in the present study to identify the physical properties of RAP recycled aggregates and to strengthen the mechanical properties of concrete mixtures incorporating RAP recycled aggregates as replacements for natural aggregates and incorporating various amounts of ZSF as industrial waste. In this regard, in the present study we also establish whether the specified aggregates were coarse or fine, the gradation curves of NA, DRAP, and WRAP recycled aggregates have been drawn. Further, few researchers have proposed that concrete pavement construction should use no more than 50% RAP in the surface course. Using literature as a basis, efforts have been made to enhance the use of WRAP aggregates in rigid pavement. Furthermore, this is a technique to improve the strength qualities of RAP recycled aggregates by using locally accessible industrial wastes and developing the co-relationship between them. For varied RAP percentages, the durability properties such as water absorption and sorptivity have also been examined. A field emission Scanning Electron Microscopy (Fe-SEM) technique was also used to further understand the micro-structure behaviour of RAP recycled aggregates and cement mortar matrix. Therefore, the objective of this laboratory investigation is to determine the optimum feasible RAP inclusion level for the manufacturing of concrete mixes based on various factors for concrete pavements in presence of ZSF.In the present study, the effect of two independent variables on a continuous dependent variable was determined by two-way ANOVA at a 5% significant level (α). In this process, the ANOVA technique was performed on Density, 28-days compressive strength, 28-days Flexural strength, and 28-days split tensile strengths to examine the significant differences between WRAP recycled aggregate-based concrete mix, DRAP recycled aggregate-based concrete mix, and reference concrete mix.Most researchers have reported that the RAP recycled aggregates are comparable to the natural aggregates so this can be used for rigid pavement construction ,35,37,51The RAP is classified into different ways of characterization in terms of washed RAP, dirty RAP, Abrasion and Attrition treated RAP, surface treated RAP, dust RAP, smooth textured RAP, and contaminated RAP ,25,55,56Ordinary Portland Cement (OPC) with a specific gravity of 3.15 as per IS: 12269-2013 was used in this current study . The ini2/g respectively  were added in different proportions. The considered admixtures, whose specific gravity and surface area were 2.3 and 18,500 cmw/c) ratio of 0.46 and naphthalene-based super-plasticizers 0.5% by weight of cement. 3 OPC has been used in the control concrete mix as a reference mix. Also, 0–30% cement weight equivalent of ZSF has been used in the concrete mix which has been considered as a partial replacement for cement.The cement concrete guidelines as per Indian Road Congress (IRC): 44-2017 criteria are followed for pavement mix design . ConcretFor this experiment, the physical and mechanical properties of used aggregates including their specific gravity, water absorption, aggregate impact, Los angles abrasion, crushing, and density was tested in compliance with IS: 2386 . To acceFlexural strength  IS: 516  using EqIS: 5816  using EqTM C 642 . The difNormally addition of silica fume (SF) to the concrete mixtures is commonly improved the mechanical properties of the concrete mix ,71. ZircIn the present study, cubes, cylinders, and beam specimens were cast and kept in square shaped curing tank in the laboratory for the specified 7 and 28 days of curing ages. The result of the 7 and 28 days compressive and split tensile strength are shown in According to the experimental results, the addition of ZSF to the concrete mix as a partial replacement of cement increased the compressive strength of the concrete. These results reveal similar trends that are consistent with all previous studies ,74,75. AOn the other hand, the 7-day split tensile strength increases with a gradual decrementing rate in the range of 3–5.3% after incorporating ZSF in the range of 5–10% in the concrete mix. A similar trend was observed in the 28-day split tensile strength as reported in The cube, cylinder, and beam specimens as prescribed the dimension earlier were cast and kept in square shaped curing tank in the laboratory for the specified 7, 28, and 56 days of curing ages. The compressive strength has achieved the target strength of control mixes at 28 days. In this sense, the addition of ZSF helps to fortify the compressive strength of various concrete mixes which can negate the effect on compressive strength caused by the incorporation of DRAP or WRAP recycled aggregate in these concrete mixes.The 7-day compressive strength was found 32.38 Mpa and 31.34 MPa for WRAP20 and WRAP40 mixes, whereas, WRAP60, WRAP80, and WRAP100 mixes reduced the strength value nearly equal to 36.8%, 36.7%, 31.6%, 2.9% and 19.3%, respectively. However, 28-day compressive strength was 48.76 Mpa and 48.4 MPa for WRAP20 and WRAP40 mixes respectively. Interestingly, a marginal difference has been observed in 28-day and 56-day compressive strength for the concrete mixes WRAP20 and WRAP40. Further addition of the WRAP recycled aggregate proportion in the concrete mixes, decreases the 28-day and 56-day compressive strength of the concrete mixes WRAP60, WRAP80, and WRAP100.A similar trend was observed in the 28-day and 56-day compressive strength of the concrete, when DRAP recycled aggregates were present in the concrete mix as a partial replacement of NA. In this regard, 7-day compressive strength was found to be 20.45, 19.85, 17.22, 16.89 and 15.48 MPa respectively for DRAP20, DRAP40, DRAP60, DRAP80, and DRAP100 concrete mixes respectively. A similar trend was observed in the 28-day and 56-day compressive strength of the DRAP20, DRAP40, DRAP60, DRAP80, and DRAP100 concrete mixes. On the other hand, the 7-day, 28-day and 56-day compressive strengths of DRAP recycled aggregate-based concrete mixes were lower than those of concrete mixes when the same proportion of WRAP was added to the mixes as a substitute for NA. It was recorded that 36.8% in DRAP20, 36.7% in DRAP40, 31.6% in DRAP60, 22.9% in DRAP80 and 19.3% in DRAP100 showed lower 28-day compressive strength compared to WRAP recycled aggregate-based concrete mixes . Similarly, a slight decrease in the 28-day and 56-day flexural strength of concrete was observed where WRAP and DRAP recycled aggregates were incorporated in the concrete mix at different proportions .Moreover, when OPC was replaced by ZSF, the compressive strength increased at the level of DRAP20, DRAP40, WRAP20 and WRAP40 type of concrete mixes at 28 and 56 days of curing. This improvement indicated the higher concentration of silica content present  in the cement concrete mixes. It has been observed that the addition of DRAP recycled aggregate or WRAP recycled aggregate as replacement of NA in concrete mix reduces the mechanical properties of concrete. As a result, the compressive strength increased as a result of the considerable amount of activated silica fume reacting with portlandite to create calcium silicate hydrated gel (C-S-H) in the hydrated sample. So, it is recommended that 10% ZSF with WRAP recycled aggregates can be used in the surface course of rigid pavements for economical and sustainable construction.Similarly to the compressive strength of concrete, the flexural strength of concrete decreased compared to the flexural strength of the reference concrete control mix after the inclusion of WRAP or DRAP. The results of split tensile strength at 7-days, 28-days and 56-days are depicted in , DRAP20, DRAP40, DRAP60, DRAP80, DRAP100). Similarly, increases in the 56-days water absorption were observed at 54.5%, 43.2%, 49.0%, 47.8%, and 63.3% for DRAP20 to WRAP20, DRAP40 to WRAP40, DRAP60 to WRAP60, DRAP80 to WRAP80, DRAP100 to WRAP100 respectively. Interestingly, the 56-day Water absorption was lower than the 28-day Water absorption of most concrete mixes.Water absorption of various concrete mixes at 28 and 56 days are illustrated in The present study found that the asphalt layer present in DRAP recycled aggregate which covers the dust layer surrounding the aggregate can primarily be attributed to the higher water absorption rate. Whereas, the addition of DRAP recycled aggregate to the concrete mix increases the water absorption capacity of that mix compared to WRAP-added concrete mix. This behaviour is consistent with the previous research ,34,35,36The sorptivity represents the variation of capillary water absorption of the concrete specimens with time√t. The first stage of sorptivity was measured for the initial rate of water absorption and the second stage was calculated for the co-efficient of sorptivity. Similarly, the co-efficient of water absorption gradually decreased in the case of similar WRAP recycled aggregates at 56 days of curing ages. However, the values of sorptivity co-efficient lead to higher water absorption for DRAP recycled aggregates at both curing ages (28 and 56 days). This phenomenon might be caused by the infilling of capillary holes by the liquefied asphalt and the water-soaking nature of considered admixtures. Moreover, these findings show that the sorptivity coefficient is higher in the DRAP recycled aggregates as compared to the WRAP recycled aggregates. This attribute may be caused in the form of the water-absorbed phenomenon due to capillary action. So, the analysis suggested from the current investigation that the WRAP recycled aggregates including the optimum content of 10% ZSF are suitable for concrete pavements and improving the strength characteristics.The microstructure of concrete mixes signifies the visualization of the morphological changes, pore structure, and interfacial transition zone (ITZ) between cement paste and aggregates in pavement structures ,77,78. PField-Emission Scanning Electron Microscopic (FE-SEM) images for RAP-based concrete with the mineral admixture ZSF as the partial substitution of OPC are shown in The two-way analysis of variance (ANOVA) normally scrutinizes the influence of two independent variables on their outcome ,83,84,85p-value is less than 0.05 at the significance level is 5% indicating that the null hypothesis is rejected. In the present study, the null hypothesis is rejected in all cases, meaning all the resulting parameters of WRAP recycled aggregate-based concrete mixes are significantly different from the resulting parameters of DRAP recycled aggregate-based concrete mixes.Broadly, the F-value obtained from the ANOVA test is greater than the F-critical and the Studies have shown that the addition of ZSF lead can improve the compressive strength of various concrete mixes which can negate the effect on compressive strength due to the incorporation of DRAP or WRAP recycled aggregate in these concrete mixes up to a certain percentage.The study also shows that up to 40% of the addition of WRAP in presence of 10% ZSF marginal change in 7-days compressive strength. WRAP60, WRAP80, and WRAP100 mixes reduced the strength value are nearly equal to 36.8%, 36.7%, 31.6%, 2.9% and 19.3% respectively with respect to the RM. Similar behaviour was observed in the 28-day and 56-day compressive strength and flexural strength of the concrete mixes.As result shows that the 7-day and 28-day split tensile strength increases with a rate in the range of 3–5.3% and 4.1–7% after incorporating ZSF in the range of 5–10% in the concrete mix. Nevertheless, there was no significant change in the 7-day and 28-day split tensile strength after incorporating 15–30% of ZSF into the concrete mix . This behaviour occurred due to the pozzolanic activity in presence of ZSF during initial the strength development phase.As the different proportions of RAP content increase, the strength of concrete tends to decrease. Interestingly, mechanical properties such as compressive strength and flexural strength increase at the 40% RAP level and reach the benchmark. Moreover, the strength was slightly reduced in the case of tensile strength of RAP aggregates-based concrete.In general, the rate of water absorption decreases within 28- and 56-days of most types of concrete mixes. This decrease (10% to 63%) takes place with the incorporation of DRAP and WRAP recycled aggregates in the concrete mix compared to the Reference concrete mix.The use of WRAP recycled aggregates in concrete mixes was proven to be advantageous in durability aspects in terms of water absorption and sorptivity characteristics of concrete.When WRAP aggregates were substituted with NCA, it was observed that the water absorption and sorptivity characteristics were found to be reduced. The present studies also recommend replacing OPC with 10% ZSF mineral admixtures found to enhance the durability characteristics of the RAP40 mix.Furthermore, it can be concluded from this current study that the partial replacement of cement by ZSF helps in improving the micro-structural bond strength which ultimately increases the value of compressive strength.It is intuitive that the incorporation of mineral additives (ZSF) would contribute to improving the strength of concrete mixes, owing to the densification of the ITZ between RAP aggregates and mortar matrix. However, the extra C-S-H gels could not greatly affect the strength properties. A very small amount of ettringite was found in considered mixtures showing the concrete pavement does not cause an adverse effect.The ANOVA model gives the right way on the different parameters of concrete strength and the results clearly indicate the replacement of ZSF in place of cement to produce higher or similar strength of RAP concrete at the optimal level. This confidence brought a greater idea to use ZSF or other by-products in RAP concrete mixes for the construction of the rigid road.This present laboratory investigation found that asphalt coating should be removed for better aggregate-mortar interaction in concrete mixes and DRAP aggregates and has needed some suitable treatments as compared to the WRAP aggregates.Consumption of RAP recycled aggregates in cement concrete pavement mixes would help minimize the utilization of natural aggregates as well as the cost of RAP concrete pavement. Henceforth, the recycling and reusing of aggregates could environmentally sustainable in terms of eliminating waste disposal issues, improving road aesthetics, reduction of carbon footprint, and being economically viable.So, it is recommended that 10% ZSF with 40% WRAP recycled aggregates can be used in the surface course of rigid pavements for economical and sustainable construction.The current study outlines the possible way to utilize WRAP or DRAP recycled aggregates in rigid pavement construction and their feasible solution for future generations. The WRAP aggregates are the beneficiary for road construction as well as the sustainable alternative to natural aggregates. Some of the concluded remarks from the present study are as follows:


On the premise of satisfying the design conditions and practical engineering needs, it is of practical significance to optimize the design of assembly components. Therefore, in this paper, based on the improved immune genetic algorithm, the structural optimization of prefabricated components is deeply studied, where it is converted into binary gene code, and the structural design requirements are introduced into the algorithm through structural layout vaccine and concrete strength vaccine. In addition, the section size of components is designed according to economic indicators, which has proved that the research is effective for the structural optimization method of prefabricated components. Since the reform and opening up, China's urbanization process has obviously accelerated, and a large number of rural people have flooded into cities with high economic development level. The limited urban land area and the expanding urban population have become one of the main social contradictions in today's developed cities in China, and more and more civil buildings adopt high-rise structures to ease the tension between population and living space –3. At thIndustrialization is a building production mode that integrates design, production, transportation, and construction and explores the deep integration of industrialization and informatization to achieve sustainable development , 8. Its In the process of building industrialization, prefabricated components are widely used. With the continuous expansion of engineering quantity and the increasing number of complex structural systems, how to meet the design conditions and the actual needs of the project in engineering practice and how to optimize its structure design are a problem worth studying. Therefore, in this paper, based on the goal of optimizing prefabricated components, an improved immune genetic algorithm is adopted, where the objective function is constructed, and the reliability, sensitivity, and dynamic balance of parameters of prefabricated structures are studied. Moreover, by designing the size of prefabricated components, the performance of components can be guaranteed, and the cost-economy index of components can be controlled, so that the optimal design of prefabricated components can be realized, and the optimal design basis can be provided for further application of prefabricated components in engineering practice. By constructing the objective function, the multiobjective is changed into a single objective, and a brand-new model to keep the dynamic balance between the objective function values is put forward, so as to control the performance of prefabricated components.Optimization of prefabricated concrete components mainly covers the following aspects: structural safety, service durability, component construction cost, production capacity of prefabricated component factory, site construction factors, component transportation, and site hoisting capacity –12. FromAs prefabricated components are mainly completed in prefabricated components factory, the water-cement ratio of prefabricated components, concrete grade, type of reinforced bar, and curing time will affect the quality of prefabricated components, and the quality of prefabricated components will affect the safety of the whole structure. The prefabrication quality shall meet the production requirements of relevant prefabricated components, so as to improve the safety of prefabricated components.The cost of prefabricated components is mainly composed of raw materials, manufacturing process, mold cost, and labor cost, among which the material cost of prefabricated components will greatly affect the selling price of prefabricated components. Therefore, considering the cost of building materials, the original design can be optimized to reduce unnecessary material loss, thus realizing the economy of building components.On the premise of considering the safety of building components, the universality of prefabricated components should be met to the greatest extent; that is, the components are similar in size, which meets the requirements of common building modules, and the combination of components can form a variety of combination schemes, so as to realize the use of the least kinds of prefabricated components. After the types of prefabricated components are reduced, the manufacturing time and economic cost of prefabricated component templates can be reduced.The dimension and length of prefabricated components shall be no more than 5 m, and the height shall be no more than 3 m, so as to meet the requirements of transportation and storage sites of prefabricated components; in addition, the dead weight of prefabricated components should not be greater than 6 tons, preferably within 4 tons, so as to meet the requirements of hoisting and temporary fixing of prefabricated components.This chapter introduces in detail the process of optimization of prefabricated concrete structure by using improved immune genetic algorithm. With the idea of combining global optimization with local optimization, the optimization of prefabricated components is regarded as the overall optimization of the structure, which is mainly used to control the overall index of the structure, while the optimization of section size of component can be regarded as local optimization of structure, which is mainly used to control the bearing capacity of the components –17.The influence of the section size of most components on the overall index of the structure is not as obvious as that of the structural layout.If all the cross-sectional dimensions are converted into binary codes as variables at the same level as the structural layout, the number of generations required for convergence will increase exponentially, and the efficiency of the algorithm will be low.The optimization of structure is divided into two levels: the first level is the optimization of concrete grade and structure layout, and the second level is the optimization of section size of components. The first-level optimization is realized by transforming specific problems into binary gene codes and carrying out population evolution, through structural layout vaccine, concrete strength vaccine, etc. In the optimization process, internal force analysis and section size adjustment need to be repeated until the total cost of the structure converges. There are two reasons for optimizing the section size of members as a second-order variable:Therefore, in this study, section optimization is carried out simultaneously in the process of structural optimization, and the interaction between the overall layout of the structure and the bearing capacity of members is considered, so that the optimization results are more reasonable.f(x) is the joint probability density function of the basic random parameter vector x=T, whose parameters are loads or random quantities representing component characteristics, and Ω={x|g(x) > 0}g(x) is a functional function or a state function, and the two states of the structure areFitness function is the main criterion for genetic algorithm to detect the effect of individual optimization, and it is also the main index for individual selection. Therefore, the structural reliability function is constructed as the objective function, and the optimization effect is evaluated. The reliability of prefabricated structure is expressed asx and functional function g(x) are expressed asConsidering that the reliability is insensitive to the change of design parameters in the design requirements of prefabricated structures, the random parameter vector ε is a parameter with small value, and the part with subscript d represents the deterministic part of random parameter. The part with subscript r represents the random part of the random parameter, and its mean is 0.Among them, β is a standardized random variable, and its probability distribution function can be approximately expanded into a standard normal distribution function according to Edgeworth series, namely,φ(y) is the probability density function of the standard normal distribution function Φ(y) and Hj(y) is Hermite polynomial. According to  of reliability can be obtained by substituting the known conditions and the calculation results of reliability analysis into (The sensitivities sis into  and 8)..∂R/∂x¯T R > 1, the sensitivity of reliability to β isWhen reliability A=∂R/∂β − φ(β); C=R(β) − Φ(β).Among them, (1)According to the previous idea of modeling, the minimum joint sensitivity of reliability is taken to the mean point of design variables as the first objective function:x=T; R0 is the reliability that should be satisfied; R is the reliability calculated by the above Edgeworth series or empirical modified formula; q(x) is the equality constraint matrix; h(x) is the inequality constraint matrix.Among them, (2)For the economic index such as the smallest volume, establish the second objective function:In order to ensure that the fabricated structure has good durability and does not suffer from performance degradation due to the change of external environment, it is required that the sensitivity of the structure to design parameters should be as small as possible. In order to meet the requirements of economic indicators such as structural lightweight, the following objective function is established:V is the volume of the structure.Among them, Compared with the volume, the reliability sensitivity function value  is small, so the following model is proposed:Among them, lg is a common logarithm and is a Gaussian rounding symbol.x changes, the new function value f1′(x) is always in the same order of magnitude as the function value f2(x), and the function value can be adjusted adaptively to achieve dynamic balance between the objectives. The implementation uses f2(x) instead of the original f1(x) for subsequent operations, which can not only achieve the dynamic balance between two objectives but also adapt to the case of more than three objective functions.No matter how the design variable wk⩾0 is the weighting factor of subobjective function fk(x) and depends on the order of magnitude and importance of each subobjective function value. wk can be determined by image set method in weighting group method, that is,n is the number of subobjective functions and xk∗ is the optimal solution vector of the k-th subtarget.According to the image set method, it can be transformed into the following single-objective problem:After the objective function of the optimized prefabricated component is constructed, the structural influence parameters are coded for population evolution. Prerequisites such as design requirements are introduced into the algorithm by vaccination, and the search mode of the algorithm is optimized to improve the overall adaptability. Finally, the section size of the fabricated structural members is optimized according to the economic indicators, and the structural optimization of prefabricated components based on improved immune genetic algorithm is completed –20.Whether the wall is arranged in the layout of prefabricated structure is a BOOL discrete variable. The binary gene coding features are just in line with the characteristics of assembly structure layout optimization variables. Therefore, this paper adopts the traditional binary coding, which contains the following information:(1) The Location of the Wall. In this paper, a 1-digit binary code is used to represent the wall layout of a grid, as shown in (2) The Length of the Wall. In this paper, the 3-digit binary code is used to represent the length of the wall in the grid. 00 represents the minimum wall length Lmin, which is 8 times the wall thickness; 11 indicates the maximum acceptable wall length Lmax of the structure. Other codes determine the wall length by linear interpolation and multiple of 50. For example, when Lmin equals 1600 mm and Lmax and LMAX equal 3500 mm, the wall length represented by code 010 is L = LMIN + 2 (LMAX-LMIN)/7 = 2143 mm.(3) Strength Grade of Concrete. In this paper, 3-digit codes are used to represent the concrete strength grade of the first floor, and the codes 000 to 111 range from C30 to C65.(1) Structural Layout Vaccine. The structural layout vaccine is used to eliminate the discontinuity of the wall from top to bottom in the structure; that is, it is considered that if the wall layout as shown in Figures There are five codes {0000, 1000, 1100, 1110, and 1111} for vaccines that can meet the continuous structural layout from top to bottom. This code set can be regarded as a temporary vaccine bank. Structural vaccine detects 100% of the vertical layout codes of walls in all individuals. Once the structural layout is found to be discontinuous, a temporary vaccine bank will be generated, and a vaccine will be randomly selected for vaccination. Vaccination of structural vaccine is always carried out in the whole evolution process, ensuring that all individuals of each generation population are always effective.(2) Concrete Strength Grade Vaccine. The concrete strength grade vaccine is used to eliminate the situation that the concrete grade in the upper layer of the structure is higher than that in the lower layer, and it is also used to avoid invalid operation. In this paper, the concrete strength grade vaccine directly adopts the lower concrete strength grade code. For example, the concrete strength grade code of an individual appears as “001010.” For a two-story structure, the meaning of this code is that the strength grade of the bottom concrete is C35, and that of the second-floor concrete is C40. However, such concrete grade distribution does not conform to the structural design habits. Therefore, the code “010” representing the strength of two-story concrete can be regarded as antigen, the code “001” representing the strength of bottom-story concrete can be regarded as vaccine, and the strength code of inoculated concrete can be changed to “001001”; that is, the second-floor adopts C35 concrete grade.The layout vaccine and concrete strength grade vaccine can be checked and vaccinated after the code is formed, which is called “Class I vaccine.” The overall vaccine is called “Class II vaccine” and can only be checked and vaccinated after the individual optimization is completed. Because “Class I vaccine” is used to avoid invalid operation, while “Class II vaccine” only replaces the individual who does not meet the overall index of the structure after changing the concrete strength grade, the fitness of the population will generally not be obviously degraded after vaccination, and the immune genetic algorithm in this paper is not necessary for “immune selection.”The convergence condition is that the difference of total structural cost for three consecutive times is less than 1%. Grid search method is an organic part of the improved immune genetic algorithm in this paper. Only after the grid search method is completed can the fitness of individuals be calculated. Set the initial section of the structure.Make analysis of internal force of the structure.Optimize the section size of the component.Judge whether the convergence condition is met; if it satisfied, the section optimization is finished; otherwise, return to step (2).The change of cross section size will inevitably lead to the redistribution of internal force of the structure, so it needs to be completed through repeated cyclic iterations. The specific process is shown in Reinforced concrete is made of two kinds of materials to resist external loads. On the premise of meeting the requirements of the minimum reinforcement ratio and the maximum height of concrete compression zone, the amount of concrete and steel bars in the section is a trade-off.Take a simply supported beam with a width of 250 mm as an example. The beam span is 3000 mm, and the bending moment in the middle of the beam is 240 Kn/m. C30 concrete and HPB400 steel bar are used as materials, and only tensile steel bar is used. By the Code for Design of Concrete Structures (6.2.10–1),The obtained height of concrete compression zone isAccording to formula (6.2.10-2) of Code for Design of Concrete Structures, it is obtained thatFive cases of beam height from 450 mm to 650 mm were investigated according to step size of 50 mm. The cost of this simply supported beam is calculated according to the unit price of concrete 500 yuan/cubic meter and the unit price of steel 5000 yuan/ton. The reinforcement is shown in Ø14 for the upper frame and Ø14@200 for the stirrup, taking 2Ø12 for the waist rebar when the section height is less than 500 mm, and 4Ø12 for the waist rebar when the section height is not less than 500 mm, without considering the template and anchorage length, the cost of this beam is shown in Assuming 2In the unit price of the two groups of materials, the lowest cost is the section height of 500 mm, with the beam reinforcement rate 1.63%. Meanwhile, when the beam section exceeds 500 mm, the cost of the beam rises again due to the increase in the number of waist tendons. Therefore, when the internal force of a component is determined, the cost of the component is completely determined by the section size, and there is always an intermediate value, which can minimize the cost of the component.Y represents that it is optional, while N represents that it is not optional). According to the optional section combination, a beam section size solution can be formed, the trial calculation is carried out in turn, and the information of the section size corresponding to the lowest fraud is selected as the optimal solution.The optimization of section size is completed by grid search method. The optimization variables of beam section include section height and section width, and the optimization variables of column section include section side lengths in different directions. To meet the requirements of modular system, the beam-column section size is a discrete variable with a step size of 50 mm, and the upper and lower limits of the variable are determined in advance. The beam sections that can be selected are shown in Once the reinforcement ratio of the section reaches the minimum reinforcement ratio, exit the inner loop , and return to the outer loop  until all feasible solutions are calculated. So there is no need to continue to enlarge the section at this time. If these solutions are converted into point sets in plane space, a grid-like graph as shown in bx,i,min and by,i min are the optimal initial length of the i-th layer column, bx,i+1,opt, by,i+1,opt are the i + 1-th layer corresponding to the optimal location column length, ti,min is the optimal initial thickness of the wall at the i + 1-th layer, and ti+1,ppt is the optimal thickness of the wall at the corresponding position of the wall at the i + 1-th layer.The optimization of section size of members starts from the top layer and goes down layer by layer. To satisfy the constraints, it is converted into the following form:With the development of building industrialization technology, prefabricated buildings will become the main part of China's future construction industry. Reasonable design of prefabricated components to ensure that they have sufficient mechanical properties and improve the economy is a hot topic of current research. In this paper, based on the improved immune genetic algorithm, the structural optimization of prefabricated components is deeply studied, where the structural optimization of prefabricated components is converted into binary gene code, and the structural design requirements are introduced into the algorithm through structural layout vaccine and concrete strength vaccine. According to the economic index, the prefabricated reinforced concrete simple-supported beam is optimized. The results show that when the internal force of the component is determined, the cost of the structural component is determined by the section size and there exists an intermediate value to reduce the cost of components to the lowest level, which proves the feasibility of optimizing the design of prefabricated structures through section size and provides a preliminary scheme for future designers of prefabricated structures.


Moreover, the environmental effects of precast concrete are evaluated. The main conclusion is that steam curing can improve the early strength of concrete, but thermal damage, shrinkage cracking, delayed ettringite formation (DEF), and other factors cause the later strength to increase more slowly or even deteriorate. Accordingly, it is necessary to undertake methods for improvement: (1) Adopt a lot of high-activity mineral admixture + a few low-activity mineral admixture combinations to ensure that the early strength of concrete meets the standard while allowing the subsequent development of concrete hydration to ensure durability. (2) Control the precuring time and temperature gradient of the concrete to allow the initial structure of the concrete to form. (3) Use effective secondary curing, such as soaking in an aqueous solution of limestone, in addition to standard curing to further improve the compactness of concrete. Moreover, the replacement of cement with less than 30% mineral admixtures in steam-cured concrete should be promoted to alleviate the environmental hazards caused by excessive CO With the rapid development and construction of national infrastructure, the demand for concrete is increasing. At this stage, concrete is mainly transported by truck and poured using pumping equipment. However, the pouring method has many drawbacks, such as pipe blockage, urban noise pollution, and insufficient strength of the concrete. As a result, precast concrete (PC) components have become widespread. Construction with PC components includes standardized building design and the production and molding of components in a factory. The components are transported to the construction site for assembly . The mos2 curing 20] desigThe temperature stress of the concrete surface intensifies and causes damage with increasing steam curing temperature. The temperature stress promotes the coarsening of the porosity of the outer layer (mainly large pores with a diameter in the range from 0.5 to approximately 4 mm) and the generation of cracks in the interface transition zones . The higHowever, the thermal damage from steam-cured concrete is hardly reflected in normal testing, which is related to the size of the concrete specimen. The concrete used in the test is generally a 100 mm × 100 mm × 100 mm cube, its hydration heat is limited, and the surface temperature is not very high. Therefore, the early strength of steam-cured concrete is greatly improved, but the later strength does not decrease in some tests .The secondary hydration of mineral admixtures with low activity is often used to compensate for the pores to effectively reduce the effect of thermal damage on concrete. Meanwhile, the steam curing process is controlled to alleviate the problem of excessive pore coarsening on the concrete surface.–6/°C in the heating stage, and the condensation of water vapor in the cooling process reduced the vapor pressure in the capillaries. The cracks occurred in the cooling stage because the concrete strength had not adequately developed to resist the shrinkage force 4− tetrahedral polymerization degree in its amorphous phase and even a three-dimensional network structure. The [SiO4]4− structure with a large degree of polymerization is not easily excited by Ca(OH)2 . Ho. Ho76]. 2-based) emissions, and global warming has led to environmental problems such as melting glaciers and extreme climate events [2 gas is released, accounting for between 5 and approximately 7% of total CO2 emissions. According to the Global Climate Summit, to achieve the goal of controlling the global temperature rise to less than 2 °C by the end of this century and maintaining it within 1.5 °C, the production of cement should be limited by 2030 to achieve the goals of the Paris Agreement and must be decreased by at least 16%. To alleviate the environmental problems caused by cement, it is imperative to promote the use of fly ash, mineral powder, and other industrial wastes in the concrete industry to replace most of the cement.Since the 21st century, the rapid development of the world’s infrastructure, economy, and energy has also resulted in excessive greenhouse gas , in which the mixed concrete is loaded into the mold and usually covered with a plastic film to maintain moisture. Shi  found thThe second stage is the heating stage of concrete (from 1 to approximately 3 h). The curing mold table is primarily heated at this stage until it achieves the highest steam curing temperature. Shi  investigThe third step is the constant temperature stage of concrete (from 2 to approximately 10 h), which is the main curing stage of concrete. The curing mold table maintains a steady high temperature and adequate water vapor to enable full hydration of the concrete and enhance the early strength. Zdeb  concludeThe fourth stage is the cooling stage of the concrete (between 1 and approximately 3 h), which corresponds to the heating process. To reduce the risk of shrinkage cracking of the concrete during this process, it is necessary to control the rate of temperature decrease.Therefore, it is necessary to control the curing time and temperature of each stage to ensure the early mechanical properties and long-term durability of steam-cured concrete.To further strengthen the early mechanical properties and durability of steam-cured concrete, effective secondary curing is often carried out on the concrete after demolding .2 promoted the microscale densification of concrete and improved its durability.Some milder curing methods, such as standard curing and water curing, can restore the chemical reaction degree of concrete and improve its compactness. Kang  added a 2S and was rehydrated to form hydration products such as CaCO3, C-S-H, and ettringite. The new products filled the microcracks and defects left by thermal damage, improving the performance of concrete.Furthermore, some scholars have compared the effects of different types of secondary curing techniques on the performance of steam-cured concrete. Zou  conducteTherefore, long-term standard curing and limestone water curing have the greatest advantages in improving the performance of PC. Effective secondary curing of PC can be carried out according to different performance and project duration requirements.2 emissions in the precuring and cooling stages, but a large amount of CO2 is produced in the heating and constant temperature stages. PC usually uses a boiler for steam curing, and the oil used in the boiler emits 2.50 kg CO2/L; 10 L of boiler oil is consumed per hour [3 of concrete emits approximately 25 kg of CO2 in 1 h [2 emission of PC in the production process is positively correlated with the total time of heating and constant temperature. Overall, the heating time is approximately 3 h, and the constant temperature time is approximately 6 h, which can ensure the performance of PC and minimize CO2 emissions. Additionally, there is a certain amount of CO2 emissions in engineering applications such as transportation and construction [2 emissions in this process are too complex for the scope of this paper and can be researched in detail in the future.PC does not produce COper hour . Therefo2 in 1 h , and thetruction . The CO22 emissions and save energy, nonsteam PC can be researched.After long-term research and practice, the steam curing regimes of prefabricated component plants have been largely perfected. However, the maximum steam curing temperature, duration, and other parameters of the curing process need to be researched in detail by balancing multiple angles to finally achieve the maximum comprehensive effect of energy and performance. Moreover, to further reduce COThe secondary curing methods in the existing research all require excessively long curing times, and the major advantage of PC lies in the rapid production of finished products and application in engineering. Therefore, in practical applications, it is necessary to improve the existing secondary curing methods and effectively replenish the concrete during long-distance transportation of PC components or sprinkle water and apply a film after the splicing and assembly are completed to ensure the performance of the concrete.This paper summarizes the effect of steam curing on concrete properties, the improvements in performance achieved by different raw material combinations and curing regimes for concrete, and the environmental effects of steam-cured concrete. The specific conclusions are as follows:(1) Steam curing can accelerate the early reaction process of cement and mineral admixtures, promote the densification of C-(A)-S-H, and promote the development of the early strength of concrete. However, steam curing also causes the degradation of the later strength of concrete. The main reasons are as follows: (1) Thermal damage: During the steam curing process, the surface temperature of the concrete is too high, and the surface pores coarsen due to the expansion of water and steam. (2) Shrinkage cracking: In the heating stage, the concrete expands greatly, and in the subsequent cooling stage, the strength of the concrete cannot resist the shrinkage force, causing cracks to form. (3) DEF: The formation of ettringite is limited during high-temperature steam curing when elements such as S and Al are present in the hydration product; when ettringite forms again in the long-term process, volume expansion causes destruction of the concrete.(2) It is not advisable to use fly ash as a mineral admixture in steam-cured concrete because it causes insufficient early strength. However, fly ash can be used with highly active admixtures such as slag to ensure that the early strength meets requirements while improving the durability of concrete. New solid waste powder and recycled aggregate, such as limestone powder, metakaolin, and discarded PC, can be used in steam-cured concrete, but traces of harmful substances must be eliminated.2 emissions during the curing process, accounting for approximately 50% of the total emissions. For steam-cured PC, it is necessary to accelerate innovation in energy technologies and promote the replacement of traditional cement with mineral admixtures to minimize CO2 emissions.(3) Compared with ordinary concrete, steam-cured PC has higher CO2 emissions. Additionally, the maximum curing temperature must be kept at approximately 60 °C and should not be too high. If conditions permit, some secondary curing methods, such as soaking in an aqueous solution of lime or standard curing, can be used to alleviate the negative effects of steam curing on concrete. It is necessary to adjust the secondary curing modes according to practical engineering applications.(4) To alleviate the lack of later strength in steam-cured concrete, it is necessary to ensure adequate curing time of the concrete and use a gentle heating method to give the concrete time to form its initial structure. A heating time of approximately 3 h, and a constant temperature time of approximately 6 h, can ensure the performance of PC and minimize CO


Daphnia magna Straus and Chlorella vulgaris Beijer, it was proven that the developed road concretes modified with the stabilizing additive “Kriogelit” do not have an acute toxic effect on the test objects and are safe for the environment and human health.Finding new ways of recycling production waste to improve the characteristics of various building materials is an urgent scientific task. This article substantiates the possibility of the disposal of fly ash in the composition of soil concrete, which is used in the construction of the structural layers of road pavements, foundations of buildings and structures, as well as sites for various purposes. The scientific novelty lies in the fact that the structure formation of soil concretes based on loam and fly ash and modified with a stabilizing additive is being studied for the first time. It was found that the investigated fly ash, according to its hydraulic properties, is classified as latent active and can be introduced into the compositions of road soil concrete modified with additives of various resources. The effectiveness of the complex method of stabilization, due to changes in soil properties as a result of the use of the binding and stabilizing additives of polymer nature “Kriogelit”, is shown. It was found that the optimal content of binder and fly ash in the samples was 8 and 10 wt.%, respectively. It was established that the use of the stabilizing additive “Kriogelit” makes it possible to obtain soil concrete with the highest strength  and frost resistance of at least F15. The microstructure, the degree of dehydration and carbonization, and the phase composition of the initial raw mixtures and soil concretes stabilized with the addition of “Kriogelit” were studied by methods of scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, thermogravimetry, and infrared spectroscopy. It was shown that organo-mineral complexes, with the participation of polymer and montmorillonite, are formed in stabilized soil concrete. It was revealed that structure formation is accompanied by the physical adsorption of the polymer on active centers of silicate minerals, carbonization, and hydration–dehydration processes. It was found that the reason for the increase in the strength of stabilized soil concretes is the hydrophobization of the porous structure of minerals, as well as the formation of calcium oxide silicate and dicalcium hydrated silicate. By the method of performing biotests with the test objects  Currently, an important ecological problem is the global anthropogenic transformation of the natural environment caused by the intense impact of industry on natural ecosystems ,2,3,4. RAt the same time, ash and slag waste is a valuable secondary raw material for various industries; therefore, the development of methods for their disposal is an urgent task. Numerous studies indicate there is a demand for ash and slag waste in the construction industry for the production of bricks and ceramics ,14,15,16Analysis of scientific and technical advances in the production of road building materials made it possible to identify ways of utilizing ash and slag waste in composites based on soils in combination with additives of various natures ,32,33,34Kianimehr et al.  researchSafi and Singh  made an The most effective way is the use of fly ash as an independent binder when strengthening sandy loam, gravel sand, and sandy soils ,55. In tThe aim of this work was to develop compositions of soil concrete based on loam and fly ash, modified with a stabilizing polymer additive “Kriogelit”, and to study the processes of their structure formation. To achieve this aim, the following tasks were completed: the study of the microstructure of samples using scanning electron microscopy, X-ray diffraction, derivation thermogravimetry, infrared spectra, and environmental safety research using biotesting.The critical improvement from the application of research results lies in the development of environmentally friendly road construction materials based on large-scale production waste.3; and the reaction of the medium pH = 8. Samples of soil concrete were obtained based on clay soil (loam) and fly ash . Portland cement with additives CEM II/A-S 32.5B  was used as a binder for the modification of mineral raw materials. To improve the performances of soil concrete, the stabilizing polymer additive “Kriogelit” was used, which is a transparent viscous liquid; the density, determined by the pycnometric method, is 1.20 g/cm3SiO5 , belite Ca2SiO4 , portlandite Ca(OH)2 , and quartz SiO2 .2 occurs after 400 °C and reaches a maximum at 462 °C. At 1150 °C, CaSO4 melts and decomposes. The differential thermogravimetric curve exhibits an asymmetric extremum at 688.1 °C, indicating the presence of carbonate impurities. Thus, the weight loss during the dissociation of carbonates is 0.82%, while the calcite stage accounts for 0.59 and 0.23%.Analyses of DSC and TG patterns in the temperature range from 25 to 1200 °C allowed, establishing that calcite is the main phase of Portland cement b. The fi2/kg and the true density is 2240 kg/m3. The value of the specific activity of natural radionuclides  is 248 Bq/kg, which makes it possible to use this waste in construction without restrictions.The grain composition of fly ash is shown in The mineralogical composition of fly ash is represented by quartz, calcite, feldspar, goethite, and the X-ray amorphous phase. Inspection of ash by DSC and TG methods reveal thermal activity of the sample a. The we−1, which is associated with stretching and bending vibrations of the CO32− group  groups. Infrared spectrum of fly ash, ν cm−1: (νCO32−) 1454, 1435; (δCO32-) 876; (νSiO2) 797, 779; (νSiO2) 692, 671; (νOH) 3458; (νSi-O-Si(Al)) 1092; (δ Si-O-Si(Al)) 461; and (δFe-O-Fe) 563. The properties of the loam are shown in According to infrared spectroscopy data, the ash contains calcite, as evidenced by absorption bands with maxima at 1454; 1435 and 876 cm2− group b. The pr2 ; albite NaAlSi3O8 ; microcline KAlSi3O8 ; and kaolinite Al2 (Si2O5) (OH)4 .X-ray diffraction analysis of the loam a made it−1 in the IR spectrum of the loam  795, 779; (νOH) 3570–3696; (νSi-O-Al) 916; and (νSi-O-Si) 1011, 1036, and 1171.Numerous absorption bands with maxima in the range of 3570–3696 cmthe loam b indicatIn this way, the initial mineral raw material belongs to multiphase polymineral systems. In this regard, when modifying them with stabilizing additives that increase the operational characteristics of the final product, it is advisable to pay attention to the homogenization of finely crushed particles. It should be taken into account that the large specific surface area of dispersed parts of loam leads to a qualitative difference in the processes of their interaction with binders and stabilizing additives.The dosages of fly ash and Portland cement in the soil concrete samples were determined experimentally. Samples in the form of cylinders with a diameter of 71.4 mm  and beamThe mixture was compacted in steel molds with a compaction load of 15 MPa. Physicomechanical characteristics were studied on samples subjected to complete water saturation after 28 days. The technological route for obtaining soil concrete with additives of fly ash and Portland cement is shown in Establishing the dependence of the physical and mechanical characteristics of the specimens on the content of Portland cement and fly ash will make it possible to regulate the strength of soil concrete. In order to establish the optimal compositions of soil concrete in the specimens, the weight fractions of Portland cement  and fly ash  were varied .The production of specimen cylinders was carried out by a hydraulic press using hollow cylindrical molds with two inserts. The compaction load was selected so as to obtain the maximum density of the specimens, which is achieved at the optimum moisture content. The molds with the mixture were kept under load for 3 min. The height of the specimens was 70 ± 1.5 mm. Specimen beams were prepared by pressing in steel molds with double-sided inserts.The compressive strength was determined on cylinder specimens of two groups: the first group of specimens was kept for 28 days in a bath with a hydraulic seal at full water saturation, the second was kept in air at a temperature of (20 ± 2) °C. Before testing the compressive strength, the specimens were immersed in water for 48 h; at first the samples were filled with water to 1/3 of the height for 6 h, and then water was added until they were completely immersed and kept for 42 h. A compressive strength was determined at a press platen speed of 3.0–0.3 mm/min.The strength of soil concrete for three-point bending was determined on samples 150 × 150 × 600 mm in size. The load increased uniformly at a rate of 0.06 MPa per second.To establish frost resistance, water-saturated specimens were loaded into a freezer and kept for 2.5 h at a temperature of minus (18 ± 2) °C. The specimens were placed at a distance of at least 50 mm from each other; the beginning of freezing was considered the moment when the temperature was set at minus 16 °C. The specimens were thawed in a water bath at a temperature of (18 ± 2) °C for 2 h, and the water layer above the specimens was at least 50 mm. The frost resistance grade was established by the number of freeze–thaw cycles, after which the strength of the specimens decreased by no more than 25%.α, U = 40 kV, I = 40 mA, Goebel mirror, Soller slit—2.5 mm, scintillation counter, 2θ = 3–60°, scanning step—0.02°, and exposure—1 s/step. The mineralogical composition of the samples was deciphered using the EVA phase search program . The reference intensity ratio (RIR) method [X-ray diffraction analysis of the mineral raw materials was performed by powder diffraction using a D8 Advance X-ray diffractometer (Bruker AXS) a: goniom) method  was carr−1 on KBr tablets. The baseline method was used to calculate the relative intensity of absorption bands.Infrared spectra were recorded with a FTIR-8400S infrared Fourier spectrometer  b in the The chemical composition of mineral raw materials was determined by inductively coupled plasma atomic emission spectrometry performed by an Optima 5300DV emission spectrometer (167–403 nm)  c. To detThermal analysis was performed using a STA 449F1 synchronous thermal analyzer  d by diffThe microstructure of the samples was examined with a JSM-6510LV scanning electron microscope  with a microanalysis system, such as the INCA Energy 350 energy dispersive X-ray spectrometer  e. A thinDaphnia magna Straus and Chlorella vulgaris Beijer. The method for establishing toxicity is based on the change in the mortality and fertility of Daphnia magna Straus under the influence of toxic substances that may be present in the investigated aqueous extract from soil concrete, in comparison with a control sample that does not contain toxic substances. The acute toxic effect of the investigated aqueous extract was determined by the mortality  of the test object for a certain period of exposure. The criterion for acute toxicity was the death of 50% or more of the Daphnia magna Straus within 96 hours. In the control experiment, the death of test objects did not exceed 10%. Test conditions with the test object Daphnia magna Straus were as follows: pH = 7.0–8.5; t = 20 ± 2 °C; dissolved oxygen was, at the beginning of biotesting ≥ 6.0 mg/dm3, and at the end ≥ 2.0 mg/dm3; dilution ratio—0, 1, 10, and 100.The determination of the environmental safety of the materials developed during the study was carried out using the method of biotesting on the test objects Chlorella vulgaris Beijer was carried out by the method of photoelectrocolorimetry. The criterion for the toxicity of the aquatic environment is a decrease of 20% or more (suppression of growth), or an increase of 30% or more (stimulation of growth) in the optical density of a culture of Chlorella vulgaris Beijer grown for 22 h in a tested aqueous extract, compared to its growth in a control medium prepared with distilled water. This makes it possible to establish the toxic concentration of individual substances or the toxic multiplicity of dilution of aqueous extracts at 22 h of light exposure in comparison with the control. Test conditions with the test object Chlorella vulgaris Beijer were as follows: pH = 7.0–8.5; t = 36.0 ± 0.5 °C.The assessment of the toxicity of the samples of aqueous extracts based on the change in the optical density of the test culture The dependence of the physical and mechanical properties of soil concrete specimens, according to 3, Ssp = 1230 cm2/g.This was due to the fact that the clay, ash, and cement components of the samples have significant water absorption. An increase in the number of freeze–thaw cycles led to a loosening and decrease in the strength characteristics of the specimens. It was found that in composites containing optimal dosages of ash (ω = 10 wt.%) and Portland cement (ω = 8 wt.%), the density and specific surface area were ρ = 2.36 g/cmash = 10 wt.%), the efficiency of using the stabilizing additive “Kriogelit” (ω = 1.0 wt.%) was studied. The maximum strength characteristics of the specimens were achieved with a mass fraction of Portland cement of 8 wt.%  in the diffractogram of stabilized soil concrete b indicat3(SiO4)O, calcium silicate Ca3SiO5, and dicalcium hydrated silicate Ca2SiO4·H2O upon the interaction of silicates with Ca(OH)2.The results obtained indicate that the reason for the increase in the strength of the samples is the formation of calcium oxide silicate CaAn increase in the strength of soil concrete can occur as a result of carbonization. By treating them with carbon dioxide, as well as hydrating cement, therefore, it is convenient to study these processes by DSC and TG methods. Analysis of the DSC curves of the initial raw material mixture and stabilized soil concrete on its basis showed the presence of several thermal effects .The endothermic effect with an extremum at 86 °C is caused by the removal of hygroscopic water, and at 162 °C by dehydration of the interlayer (adsorption) water of montmorillonite a. The enTemperature shifts of endothermic effects at 107 and 692 °C on the DSC curve of the stabilized soil concrete b, explaiThe TG curves are also different, despite the fact that the total weight loss at t = 798 °C for the raw mixture and the stabilized soil concrete based on it have close values of 5.79 and 5.40%, respectively. It was found that, in comparison with the initial raw mixture, at first the weight loss occurs more slowly (up to a temperature of 360 °C), and then faster. The appearance on the DSC curve of the exothermic effect at 340 °C with a loss of mass on the TG curve is due to the decomposition of organic compounds bound into organomineral complexes b. In addThe formation of colloidal “calcium-polymer compounds” in soil concretes is characterized by poor water retention. In this case, the thermogram and diffractogram should show thermal effects and reflections related to new growths and absent in the initial materials, which is not observed in this case . Thus, uThe structure of the raw mix and the stabilized soil concrete obtained on its basis was studied by infrared spectroscopy .−1, the intensities of which decrease after the addition of the stabilizing additive “Kriogelit”. This is due to the displacement of water molecules by the polymer and the blocking of active hydrophilic centers of smectites. New absorption bands are recorded at 2926 and 2855 cm−1, characteristic of the CH groups of the polymeric organic additive. The hydrophobizing activity of the additive “Kriogelit” is visible due to the decrease in the intensity of the absorption bands of stretching and bending vibrations of OH groups in interlayer water, which is associated with the penetration of stabilizer macromolecules into the montmorillonite gallery.In the infrared spectrum of the initial raw material mixture a, absorp−1 stretching vibrations of the CO32− group are enhanced in the spectrum of stabilized soil concrete, and an absorption band of deformation vibrations of this group appears at 878 cm−1, which indicates the ongoing carbonization process. The absorption band at 3622 cm−1 belongs to the Si-OH groups and indicates the hydroxylation of the mineral surface. A shift of the absorption bands of Si-O-Si is observed; OH and CO32− groups with a change in their intensity in the spectrum of stabilized soil concrete , and frost resistance of at least F15.-It was revealed that the stabilizing additive “Kriogelit” promotes the formation of secondary soil microconglamerates and dense coagulation structure in soil concrete. In the process of structure formation, a crystallization framework of calcium silicate hydrates and calcium oxide-silicates is formed, as well as a coagulation framework of clay and dusty particles interconnected through thin layers of water and polymer. Carbonization and the formation of organomineral complexes during polymer intercalation to montmorillonite contribute to structure formation. According to its effect on the soil, the stabilizing additive “Kriogelit” is a “stabilizer-hydrophobizator”, which manifests itself in the blocking of active hydrophilic centers of smectites and quartz. In order to increase the adsorption capacity of the stabilizing additive, the minerals of the original raw mixture can be arranged in the following order: montmorillonite > microcline (feldspars) > quartz > albite.-Daphnia magna Straus; Chlorella vulgaris Beijer) and are safe for the environment and human health.The ecological safety of soil concrete modified with the stabilizing additive “Kriogelit” was established. It was proven by the biotesting method that the developed soil concretes do not have an acute toxic effect on test objects (This study is aimed at developing compositions of soil concrete based on loam and fly ash, modified with a stabilizing polymer additive “Kriogelit”, and studying the processes of their structure formation. Based on the results, the following conclusions were made:Potentially, the application of the research lies in the development of environmentally friendly road building materials based on large-scale production wastes. Prospects for further research can be aimed at studying the features of the restoration of damaged and degraded ecosystems after the elimination of the waste dumps of enterprises.


In this binder, calcium hydroxide was included as an alkali stimulant but Portland cement was not included. Experiments on the compressive strength and durability of this type of material were conducted and its applicability to precast concrete products was investigated using full-scale specimens. The experiments proved that high-temperature steam curing is effective at obtaining strength development and that compressive strength can be expressed as a linear function of the binder–water ratio. Experimental results of chloride ion diffusion coefficient and sulfuric acid resistance suggested that the proposed material has higher resistances than conventional cement concrete against these deterioration factors. It was also demonstrated that full-scale specimens of a box culvert and a centrifugally compacted pipe using this type of material have almost the same load-bearing capacity and deformation performance as those using conventional cement concrete. It is believed that the proposed material could be used as a construction material instead of cement concrete, contribute to reducing CO Moreover, a large part of the infrastructure built during the period of rapid economic growth has deteriorated, leading to calls for countermeasures. In these circumstances, demand has increased for precast concrete products that provide high quality, high durability, and high construction efficiency. Meanwhile, reducing the burden on the global environment has become a pressing issue in the field of concrete technology. Effective solutions to this problem include reductions in the amount of cement used, which cause large COTherefore, attempts have been made to use large amounts of industrial by-products as supplementary cementitious materials in order to suppress the cement content of concrete. These include a method with significantly high ratios of ground granulated blast furnace slag (BFS) and fly ash (FA) in place of cement. In recent years, there have been studies in which the ratios of these materials in the binder were drastically raised to eliminate cement for precast concrete products. Under these circumstances, many researchers have studied the alkali-activated material known as geopolymer ,2, whichRegarding applications to concrete structures, they have been applied to the street–sideway boundary blocks  and sleeHowever, the production of the above-mentioned geopolymers generally requires the handling of concentrated aqueous alkali solutions, which are corrosive, viscous, and difficult to handle. Furthermore, the reaction of an alkali metal source with silicate powder is essentially needed in addition to the mixing process with water. Therefore, it is desirable that this kind of material be user-friendly, such as conventional cement concrete, and could be manufactured by simply adding water to the powder . As a re2. Its durability was also experimentally examined in terms of the chloride ion-shielding capability and sulfuric acid resistance required for precast concrete products depending on their uses and environmental conditions. Furthermore, mock-up specimens of box culverts and Hume pipes using IBPM concrete were prepared to evaluate the load-bearing performance.Under these backgrounds, the goal of this study involves the application of alkali-activated cementless material to steam-cured precast concrete products. Among various types of alkali-activated materials, this research focuses on user-friendly mixtures containing FA and BFS that can be used simply by adding water to the powder and mixing . In thisFA and BFS, which are the major components of IBPM concrete, were proportioned to FA:BFS = 4:6 by mass;SF, expecting the effect of improving workability of the IBPM concrete, was added to 5% of the binder. This is because the workability of concrete with a low water–binder ratio is possibly improved by adding several percent of SF, which is extremely finer than the main particles, to increase the particle filling rate ;3 of IBPM concrete, was selected for IBPM-1 to be nearly equivalent to the general content of 30 kg/m3 for OPC concrete. Moreover, the EX content of IBPM-2 was 11.1%, which was twice that of IBPM-1, to investigate its effect on the compressive strength of IBPM concrete;The EX content of 6.0%, in view of the binder content (IBPM content) of around 500 kg/mThe content of CH  was around 4.0% in order to achieve good strength development based on the test results of IBPM mortar with W/B of 0.34. In this test, the specimens were subjected to steam curing, shown in As listed in 3. Furthermore, it was also found that the proper workability for the executions of Hume pipes and box culverts could be obtained with IBPM concrete, which is described in 3. Coarse aggregate was, therefore, added after the mortar attained sufficient workability, and was then further mixed. It took approximately 8 min from the beginning to the end of mixing.Mixing of IBPM concrete was conducted with a biaxial forced mixer with a capacity of 60 L, as shown in From the experimental results reported in a previous study , it was 2 at the age of 1 day. As a result, the concrete was still in a fragile state and adhered to the surface of the formwork, causing partial separation, and making it difficult to remove the formwork. On the other hand, in the case of steam curing, the compressive strength was 33 N/mm2 at the age of 1 day after the completion of steam curing [According to previous studies , the comm curing . Based oIn this study, the hydration products were identified by powder X-ray diffractometry (XRD) using IBPM paste with a W/B of 0.3, where B is the total mass of IBPM. Note that the IBPM paste specimens were steam-cured and then air-cured until the age of 91 days. Pore size distributions of the IBPM paste and OPC paste were measured by a mercury intrusion porosimeter using the above-mentioned paste specimens. As shown in A compressive strength test of IBPM concrete was carried out using cylindrical specimens (100 mm in diameter and 200 mm high). Specimens were subjected to steam curing as given in 2 by reducing the water–binder ratio (W/B) to around 0.2, corresponding to a B/W of 5.0. 2, the mix proportion design based on compressive strength can be conducted using the fitting lines shown in 2.3, C = 420 kg/m3, S = 810 kg/m3, G = 1009 kg/m2, and Sp = 4.20 kg/m3). The drilled core specimens were immersed in an aquatic solution with a chloride ion concentration of 10%. Note that the 14-day compressive strengths of IBPM and OPC concretes, which were steam-cured as given in 2, respectively.The chloride ion-shielding property of concrete is important for precast concrete products in a chloride-laden environment, such as box culverts constructed underground along the coast. In this study, cylindrical specimens (50 mm in diameter and 100 mm in length) that were drilled from the mock-up specimens for box culverts were used. The details of the mock-up specimen are shown in 3 at the maximum, with the penetration depth being 9 mm or less, whereas that of OPC concrete was 24 kg/m3 at the maximum, and the penetration was around 18 mm. In accordance with the standard method [D in the equation.x (cm) from the exposed surface, erf is the error function.d method ,23, the 2/year, respectively. The diffusion coefficient of IBPM concrete was, thus, found to be significantly low, approximately one-fifth of that of OPC. It is suggested that the denser microstructure of IBPM, which is discussed in The fitting curves by Equation (1) are also shown in 3, C = 440 kg/m3, S = 734 kg/m3, G = 1076 kg/m3, and Sp = 3.52 kg/m3) were also prepared. It should be noted that the 14-day compressive strengths of IBPM and OPC concrete were 71.3 and 53.2 N/mm2, respectively.Resistance to the sulfuric acid of concrete is important for precast concrete products, such as sewer pipes, which are subject to deterioration by sulfuric acid. This is a phenomenon in which sulfate in sewer pipes changes to hydrogen sulfide and then to sulfuric acid due to the bacterial action, causing the concrete to deteriorate. In order to evaluate the resistance to sulfuric acid of Hume pipes, tubular specimens with IBPM and OPC concrete were fabricated by vibratory or centrifugal compaction and subjected to steam curing under the condition given in After immersion in the sulfuric acid aqueous solution for 112 days, the test pieces measuring 40 by 40 by 20 mm were cut from the inner surfaces of the specimens to measure the depths of the scaled portions. Since some particles of coarse aggregates were exposed on the surface of the severely deteriorated OPC concrete specimens, the depth of the scaled portion of the OPC test piece was measured on the surface of the mortar phase between coarse aggregate particles. The depth of the sulfur penetration was also examined by EPMA using the same test pieces as those for measurements of the scaled portions. As shown in In the previous section, the compressive strength and durability of IBPM concrete were discussed based on experiments, and the possibility of application to precast concrete products was suggested. Therefore, mock-up specimens of the box culvert and two kinds of Hume pipes were produced at a precast concrete product factory. During the production of the mock-up specimens with IBPM concrete, it was confirmed that placement, compaction, and surface finishing could be properly conducted with the same equipment and procedures as those for mock-up specimens with ordinary Portland cement. In the following sections, the load-bearing capacities of IBPM precast concrete products are demonstrated based on the experiments with full-scale specimens of a box culvert and two kinds of Hume pipes.There are two kinds of construction methods for Hume pipes, the open-cut method and the jacking method. The former is a method in which a trench is excavated and pipes are laid therein, whereas the latter is a trenchless method in which pipes are pushed into the soil from a working well with a jacking system, minimizing traffic restriction. In this study, mock-up specimens of Hume pipe A (for open-cut construction) and Hume pipe B (for jacking construction) were fabricated at a precast concrete plant. Based on the relationship between the B/W and compressive strength of IBPM concrete previously mentioned, the W/B of IBPM concrete for Hume pipes A and B were determined to be 0.26 and 0.22, respectively, to obtain each target of compressive strength.The mock-up specimen for Hume pipe A has dimensions of 300 mm of internal diameter, 30 mm of thickness, and 2000 mm in length, as shown in 2, respectively. The judgment criterion for the cracking load was the load at which a crack of 0.05 mm in width was visually recognized. The fracture load was the load at a point at which an extra load no longer increased during the loading tests. The load-bearing performance of the mock-up specimens of Hume pipe A and Hume pipe B were evaluated by static loading tests in accordance with Japanese standards, JIS A 5372 , JSWAS AMock-up specimens for box culverts were also prepared at a precast concrete plant. Based on the above-mentioned W/B-strength relationship of IBPM concrete, the W/B of IBPM concrete was determined to be 0.21. 2. It can be seen from The load-bearing performances of the mock-up specimens of box culverts were evaluated by the tests in accordance with JSWAS A-12  as shown2 emissions from the production of IBPM concrete in comparison to that of OPC concrete, trial calculations were carried out for the box culvert and Hume pipe. In the calculations, the CO2 emission intensities of each material shown in 2/t, respectively [2 emission of IBPM-2 was 136.9 kg-CO2/t, which was much less than that of OPC. Then, the CO2 emissions of the box culvert and Hume pipe B were calculated based on their mix proportions of concrete, which are shown in 2 emission per 1 m3 of IBPM concrete was 81.2 kg for the box culvert and 73.2 kg for Hume pipe B. These values were only 25% and 21% of those of the corresponding products with OPC concrete, respectively. Since steam curing is generally applied to precast concrete products regardless of the binder type, the CO2 emission due to energy consumption of the steam curing was also considered. When the CO2 emission intensity of heavy oil was assumed to be 2.91 kg-CO2/L [2 emissions of precast concrete products.In order to estimate the COectively . It can kg-CO2/L , the ratIn this study, cementless binder ) was proposed as material for steam-cured precast concrete products. Within the range of the experimental conditions, the findings are summarized as follows.2 can be produced by high-temperature steam curing. The compressive strength of IBPM concrete is related to its binder–water ratio, with the relationships expressed by different straight lines depending on the expansive additive content.It is proved that IBPM concrete with compressive strength from 40 to 80 N/mm3.Increases in the binder content in IBPM concrete mixtures with decreases in the water–binder ratio can be suppressed by reducing the unit water content down to around 105–120 kg/mThe chloride ion diffusion coefficient of IBPM concrete is approximately one-fifth of that of OPC concrete.The inner surface of the Hume pipe with IBPM concrete made by the centrifugal compaction method rarely suffers deterioration by sulfuric acid.From the test results of static loading on the mock-up specimens, it is suggested that precast concrete box culverts and Hume pipes with IBPM concrete have almost the same load-bearing capacities and deformation performances as those of OPC concrete.