Search

This study investigates the impact of incorporating lime mud (LM) as a filler material to develop sustainable, cementless ultra-high performance concrete (UHPC) by replacing silica powder (SP) and silica sand (SS) at varying percentages. Flowability analysis reveals that LM, with its distinctive particle size, influences flow characteristics differently at different replacement levels. Compressive strength was improved by 5.4% with 30% SP replacement, showcasing the role of LM in nucleation, as well as its particle size advantage. The heat of hydration analysis indicates that LM likely influences the early curing stages, enhancing reactivity and nucleation. TGA analysis also confirms that LM plays a role in hydration reaction, influencing weight loss and hydration peaks. The mercury intrusion porosimeter results show the impact of LM on pore distribution, with 30% for SP and 50% for SS replacements, favoring denser matrices. Life cycle assessment (LCA) demonstrates reduced CO 2 emissions and favorable environmental performance, highlighting the sustainability potential of LM replacements. Overall, the incorporation of LM in UHPC shows promise in terms of enhancing its mechanical properties and environmental sustainability. [Display omitted] • Lime mud (LM) in UHPC boosts material strength, leading to denser, more effective concrete. • LM enhances hydration, flowability, and refines pore structure. • High LM ratios in UHPC increase sustainability and reduce CO 2 emissions. • LM's use in UHPC significantly advances its mechanical properties and eco-friendliness. [ABSTRACT FROM AUTHOR]

In recent years, with the improvement of construction safety requirements in deep well mining, the backfill mining method has been widely used. However, the strength of paste filling acquired in quarry often surpasses the design strength determined in laboratory settings. In view of the problems that indoor conditions cannot restore deep mining environment, and the mechanism of coupling effect under multiple fields is unclear. This paper has carried out relevant research work through theoretical analysis and indoor experiments. First of all, after completing the preparatory experiments, this paper analyzed the strength difference of backfill under different curing stress and drainage conditions, and studies the influence of different curing conditions on the strength. Secondly, MPS-6 and 5TE sensors were used to monitor the electrical conductivity, pore water pressure, porosity and other parameters of backfill during the stress-drainage curing process, and changes of parameters during curing process were analyzed. Finally, the relationship among relevant parameters and strength properties of paste backfill was analyzed, as to clarify the influence mechanism of stress-drainage curing conditions on the strength formation for paste backfill. Research shows that both stress-undrained and stress-drained conditions can effectively increase the strength of backfill. Under stress-drainage conditions, the internal porosity of backfill will decrease, and the pore water pressure of backfill will first increase slightly and then continue to decrease. Under this condition, the electrical conductivity of backfill will first increase and then continue to decrease. The entire research has important positive significance for reducing mining costs, optimizing mining processes, and developing mining technology. • The instrument is a self-developed equipment, which can monitor changes of backfill in real time. • The test blocks were cured under different stress and drainage conditions. • Binarize the scanned image of samples, and then use ImageJ to analyze the processed image. • Combined with two sensors, the relationship between microscopic parameters and strength can be explored. [ABSTRACT FROM AUTHOR]

To study the differences in material performance between HRB400E steel and conventional strength steel, this paper performed monotonic and cyclic loading tests on HRB400E and Q355B steels under a series of loading protocols. Additionally, the self-designed fixtures were used to achieve large strain rate loading. The ductility, monotonic behavior and hysteretic characteristics of HRB400E and Q355B steels were assessed, along with the energy dissipation capacity evaluated through the energy dissipation coefficients. The cyclic skeleton curves of both steels were fitted using the Ramberg-Osgood model, with further investigation into the influence of kinematic hardening parameters on hysteretic curves. The combined hardening parameters of the Voce-Chaboche model were calibrated based on the experimental results, and the hysteretic curves were simulated under different loading protocols via ANSYS. The analysis results reveal that the energy dissipation coefficients of HRB400E steel are larger than that of Q355B steel, yet smaller than those of Q460D, LYP100, LY100, LY160, and LY225 steels. Both HRB400E and Q355B steels demonstrate significantly improved material strength under cyclic loading. Excellent agreement between simulated and experimental curves is achieved when using four pairs of kinematic hardening parameters. Additionally, the hysteretic performance of HRB400E and Q355B steels under different cyclic loading protocols can be precisely simulated by employing calibrated combined hardening parameters. Through this paper, the cyclic behavior and constitutive relations of HRB400E steel are comprehensively understood, which provides a reliable theoretical basis for engineering design and structural analysis. Furthermore, this research provides a scientific basis for material applications of HRB400E steel. • HRB400E steel and conventional strength steel are compared in material performance. • Monotonic and cyclic loading tests are conducted. • Ductility, monotonic property, and hysteretic performance of HRB400E and Q355B steels are assessed. • Self-designed fixtures are utilized to achieve large strain rate loading. • The hysteretic property of the HRB400E steel can be accurately simulated. [ABSTRACT FROM AUTHOR]

Reinforced concrete is a commonly used material for constructing basements in low-rise buildings or residential houses in Canada, and as the use of cross-laminated timber (CLT) advances, the door to think of an alternative basement material to offset greenhouse gas emissions associated with reinforced concrete is open. However, the evaluation of CLT durability in below-grade environments, specifically concerning moisture and mould development, remains an unexplored field in research. Hence, this paper aims to analyze CLT's moisture response and mould growth risk in below-grade environments using field and laboratory experiments. A laboratory experiment was carried out to test a waterproofing membrane solution selected to compose the wall assembly in the field experiment. A large-scale experimental CLT basement was built at a cohesive soil site in Edmonton, Canada. The field experiment involved monitoring the relative humidity, temperature, and soil volumetric water content of the CLT panels, which measure 3 m by 6 m in plan and 2 m deep. Data was collected for an extended period from June 2022 to July 2023. The VVT model, developed by Hukka and Viitanen (1999) and updated by Viitanen et al., 2011 to estimate the mould growth level, was used to predict the risk of mould growth. The laboratory experiment showed that the waterproofing membrane is suitable for protection against moisture in a still-water setup. Field experiment results suggested that the primary moisture source was below the basement floor when the floor was finished inadequately. The moisture content of CLT walls was significantly increased by floor flooding and decreased by heating the basement interior. The acceptable mould index of three was surpassed during periods of abundant water below the basement floor due to flood events, showing that the CLT panels were at risk of mould growth development. • CLT use inbasements is in research stage. This paper contains insights for developing future research on this subject. • CLT in basement construction requires robust envelope with waterproofing membranes that perform well below grade. • Elevated moisture levels could pose structural and biological risks to the CLT basement and its occupants. • CLT basement walls take time to dry, and during this period, the walls may be exposed to risky levels of mould growth. [ABSTRACT FROM AUTHOR]

3D printing technology revolutionizes construction by creating custom building components with increased efficiency and reduced waste. This paper reviews advancements in the 3D printing of cementitious materials, focusing on integrating mineral additives (MAs) like metakaolin, micro-silica, slag, and fly ash to address environmental and economic challenges linked with high-Portland cement content in 3D concrete printing (3DCP). MAs enhance the pumpability, printability, and buildability of 3DCP while reducing its environmental impact. The review emphasizes optimizing cement mixtures, including alkali-activated materials, to enhance sustainability and performance. It discusses the mixture design's importance, balancing mechanical properties and environmental impacts, and examines MAs' influence on rheological properties, mechanical performance, and 3DCP durability, including layer bond strength. The paper also discusses global 3D printing technology adoption in construction and challenges in additive manufacturing implementation. By analyzing printing parameters, mixture proportions, and materials' effects on long-term performance, this review highlights 3D printing's potential for economically viable and eco-friendly structural elements. It aims to guide future advancements in 3D printable cementitious materials, meeting modern construction demands while addressing traditional concrete production's environmental challenges. • Using recycled mineral additives reduces 3D-concrete printing's environmental impact. • Optimizing printing parameters strengthens layer bonds in 3D-concrete printing. • Recycled materials promote sustainability and innovation in 3D-concrete printing. [ABSTRACT FROM AUTHOR]

Grouting is one of the most commonly used methods to control water inrush disasters in fractured rock mass. At present, most of the research on the diffusion process of fracture grouting is carried out on the hypothesize that the groundwater was completely displaced by the slurry, which is lack of sufficient theoretical basis. Therefore, a one-dimensional visual fracture grouting experimental system was developed and a new characterization method of slurry concentration based on the image gray level was proposed in this paper in order to characterize the variation law of slurry-water mixing region during the grouting process. Results show that there exists slurry-water mixing region at the frontal surface of the diffusion slurry in the grouting process in fractured rock mass. The slurry-water mixing region can be characterized by the gray level of the images captured by cameras. The relationship of water to cement ratio of slurry (w/c) and image gray level of slurry (G) conforms to linear function, which can be expressed by G = 19.17 w/c when w/c is between 0.8 and 10. In addition, slurry concentration decreased linearly along the diffusion flow path in the slurry-water mixing region. The size of slurry-water mixing region is positively related to grouting flow rate, the mass ratio of water to cement (w/c) and fracture aperture when the grouting flow rate is between 0.6 L/min to 2.4 L/min, w/c is between 0.8 and 1.6 and fracture aperture is between 1 mm to 5 mm. Furthermore, the ratio of slurry-water mixing region size to hypothetical diffusion radius (RSR) was proposed to characterize development degree of slurry-water mixing region. The stable value of RSR was between 0.04 and 0.24 under the experimental conditions in this paper. The index of RSR can be used to provide theoretical basis for the simplification of the interface between slurry and water. The distribution rules of the slurry-water mixing region can be applied to predict the diffusion range more accurately and perfect the grouting theory. • Image gray level method was introduced to characterize the variation of slurry-water mixing region during grouting process. • Experimental system for simulation of one-dimensional visual fracture grouting was presented. • The ratio of slurry-water mixing region size to hypothetical diffusion radius was developed. [ABSTRACT FROM AUTHOR]

This paper investigates the behavior of reinforced concrete (RC) arch beams with shear weaknesses strengthened with fiber-reinforced polymer (FRP) composites, using two different methods: the externally bonded reinforcement (EBR) and grooving method (GM) in the form of externally bonded reinforcement on grooves (EBROG) method. Additionally, two different patterns of shear strengthening including two-sided and U-shaped were utilized. Nine arch beam specimens were tested, each having a square cross-section of 150 mm and a span length of 947 mm. Among these, two specimens were strengthened using the EBR method, while six specimens were strengthened using the EBROG method. The paper explores the impact of the strengthening method and pattern on the load-carrying capacity, failure mode, energy dissipation, and strain distribution of the specimens. The results indicate that the EBROG method significantly increased the load-carrying capacity of the arch beams compared to the EBR method in both patterns. The results also show that the U-shaped pattern was more effective than the two-sided pattern in increasing the load-carrying capacity of the specimens. The specimen with intermittent U-shaped FRP demonstrated 34.8% and 47.3% higher load-carrying capacity than the non-strengthened specimen when using the EBR and EBROG methods, respectively. The paper also introduces an analytical approach to estimating internal forces, such as flexural moment, axial force, and shear force, along the arch beam. The comparison between the experimental and theoretical results confirms the accuracy of the analytical approach. • The behavior of RC arch beam with shear weakness was investigated. • EBR and EBROG methods were adopted for strengthening of the arch beam. • PIV method was utilized to obtain the strain distribution, validate the displacements, etc. • An analytical procedure was conducted to validate the experimental results and investigate the performance of the strengthening methods. [ABSTRACT FROM AUTHOR]

This paper studies the effect of high temperatures (20℃, 200℃, 400℃, and 600℃) and stress ratios ( σ 2 / σ 3 ) (0.15, 0.3, 0.45, and 0.60) on biaxial compressive strength and strain development patterns of high-strength geopolymer concrete (HGPC). Experimental observations indicate that HGPC exhibits laminar damage similar to ordinary Portland concrete (OPC) before and after exposure to high temperatures, under biaxial compression. Unlike OPC, damage in HGPC initially passes through coarse aggregates at room temperature but shifts predominantly to the aggregate-mortar interface at 600℃. The biaxial compressive strength envelope of HGPC expands with rising temperatures. The increased multiple of biaxial compressive strength ( σ 3 / f m ) for HGPC at room temperature rises and then falls with increasing stress ratios, peaking at a stress ratio of 0.45 and surpassing the values for OPC and high-strength concrete (HSC). Before high temperature, the modulus of elasticity of HGPC is higher than that of OPC and decreases with increasing temperature, decreasing by about 45–60% for every 200°C increase, and the reduction is greater than that of OPC. The existing failure criterion is not suitable for HGPC after high temperature, this paper develops a new biaxial compression failure criterion for HGPC before and after high temperature based on Kupfer's criterion, taking into account the effect of temperature. The proposed failure criterion calculation results are well in agreement with the experimental data. A damage constitutive model for HGPC considering the effect of temperature and lateral pressure is also proposed, combining the Weibull distribution model for the ascending branch and a modified empirical model for the descending branch. This combined model effectively predicts the stress-strain relationship of HGPC under various temperature conditions. • The axial behavior of HGPC is tested at different temperatures and lateral pressures. • A failure criterion for biaxial compression of HGPC taking into account the effect of temperature is proposed. • A damage constitutive model of HGPC considering the effect of temperature and lateral pressure is established. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of bond in post-tensioning strands in the presence of grout injection defects. In particular, the paper describes a campaign of experimental pull-out tests with a single 7-wire steel strand in the centre of a galvanised sheet metal duct with no grouting defects and with 25% and 50% defects, i.e. voids in the cross-section area of the grout. The grouted length is short in order to obtain a local bond–slip relationship. This relationship has an initial branch followed by a jump descent and a subsequent growing branch in the form of a sawtooth. The experimental data are used to define a specific bond–slip relationship that takes into account the presence of defects. The results show that the obtained bond–slip law is very different from those proposed in the literature for the case of ribbed steel bars. Furthermore, the defects cause a decrease in bond stresses and a flattening of the shape of bond–slip curves. • Bond of post-tensioning strands is studied. • Experimental pull-out tests are performed. • Effect of grout injection defects is investigated experimentally. • A bond-slip relationship for post-tensioning strands with defects is proposed. [ABSTRACT FROM AUTHOR]

Engineered Cementitious Composites (ECC) utilize the bridging effect of high toughness fibers to improve the brittle failure of concrete materials, achieve the effective control of cracks in cementitious materials, and significantly improve the deformation capacity. In view of the multi-stage crack-blocking effect of different fibers incorporated in ECC materials, 91 ECC specimens of steel-polypropylene hybrid fiber by mixing steel fiber (SF) and polypropylene fiber (PPF) into cement-base are made in this paper. The specimens are tested in compression, tensile, bending and damping properties, respectively, which is of great significance to study the response of ECC structures under the earthquake action. The effects of the volume content of SF and PPF on the mechanical properties of ECC are studied in this paper. The results show that the cube specimen has better ductility than the prismatic specimen under monotonic compression, and there is no obvious brittle failure. With the increase of the volume content of SF to PPF, the compressive strength and elastic modulus of hybrid fiber ECC gradually increase, while the corresponding strain and axial compressive toughness gradually decrease; the tensile strength and tensile modulus increase, while the bending strength and damping ratio decrease. According to the test results, constitutive models of monotonic and repeated loading of hybrid fiber ECC suitable for finite element (FE) analysis are proposed. This investigation provides a theoretical basis and an experimental reference for further study of steel-polypropylene hybrid fiber ECC. • Steel fiber and polypropylene fiber are mixed as hybrid fiber of ECC. • The mechanical properties of ECC are investigate. • Volume content of steel-polypropylene hybrid fiber has influence on concrete material. • The hybrid fiber ECC cube has better ductility than that of prismatic. • Constitutive models of hybrid fiber ECC are suitable for finite element analysis. [ABSTRACT FROM AUTHOR]

This paper focuses on the experimental and analytical behavior assessment of novel sandwich panels fabricated with recycled glass-fiber/polyester resin (GFRP) core and PVC face sheets. The originality of the present work is based on sustainable development and waste recovery to design lightweight and eco-friendly structures. In this respect, the panels cores were fabricated using fully recycling of fiber-glass waste issued form the boats building. Accordingly, a set of sandwich panels with various core configuration and fibers orientation were manufactured and tested up to failure under three-point bending to characterize flexural and shear properties. In addition, validated analytical equations were advocated to assess the bearing capacity of the studied panels. The obtained results in terms of mechanical, thermal and physical features are emphasized, discussed and confronted with a good agreement to literature ones. A principal component analysis was conducted to optimize the effect of the geometrical parameters on the panel failure mechanisms. As main outcomes, the work can provide environmental and economic solutions for the design of sandwich structures. • Lightweight and eco-friendly sandwich structures-based GFRP waste core were designed • Validated analytical equations were advocated to assess the bearing capacity of the studied panels under bending • A principal component analysis was conducted to optimize the geometric parameters of the panels • The paper results provide environmental and economic solutions for the design of sandwich structures [ABSTRACT FROM AUTHOR]

The maintenance design for existing asphalt pavements, characterized by their typical structure and material composition, falls short of meeting the diverse requirements of pavements. There is an urgent need for a more rational design approach that can achieve accurate pavement design while also reducing construction costs. This paper focuses on selected conventional road surface structures and conducts an analysis of how pavement structure and materials impact fatigue life and construction expenses. It employs Python to perform three-dimensional finite element road modeling, analysis, and data extraction at specific locations, using normalized fatigue equation to calculate pavement fatigue life. The optimization variables selected are the modulus E and thickness h, with pavement maintenance cost serving as the optimization target function. The particle swarm optimization algorithm is employed for optimizing these variables. A comparative analysis is carried out for five improved optimization algorithms, optimizing combinations of inertia weight, learning factors, particle speed, number of particles, and iteration times. The results reveal that the enhanced optimization algorithms significantly improve iteration trends, featuring velocity limitations and natural selection mechanisms. Between 0 and 20 iterations, all algorithms search for the optimal solution over a wider interval with greater fluctuations. Between 20 and 30 iterations, each algorithm gradually converges towards its solution, stabilizing in the later stages. Based on optimization speed and actual engineering cost benchmarks, the NDPSO algorithm is selected, resulting in a 52.8% reduction in actual engineering costs. Adjustments to the particle count and iteration number of the NDPSO algorithm are made based on computational cost and optimization accuracy, thus choosing 20 particles and 50 iterations as the recommended parameter combination. By combining automated finite element modeling, analysis, and particle swarm optimization, this paper offers a novel and effective automated design reference for extending the lifespan of asphalt pavement structures. • An improved particle swarm optimization model for fatigue life with consideration of the modulus E and thickness h. • The automation of finite element modeling, calculation and data extraction is completed by using further development. • Normalized fatigue equation is used to calculate pavement fatigue life. • A novel and effective automated design reference for extending the lifespan of asphalt pavement structures is proposed. [ABSTRACT FROM AUTHOR]

This paper presents a thorough investigation into utilizing hybrid fibers, comprising both steel and polymeric fibers, to enhance the compressive and tensile behaviors of ultra-high-performance concrete (UHPC). Flowability tests revealed potential usability challenges with polymeric fibers, emphasizing the necessity for careful consideration. Compressive strength results demonstrated that hybridizing straight steel fibers with short hooked steel fibers results in performance similar to that of reduced steel fiber content. Elastic modulus trends correspond with those of the compressive strength, and unexpectedly positive effects on the ultimate strain capacity under compression are observed with long polyvinyl alcohol fibers. Tensile behavior analysis highlights the superiority of both short and long hooked steel fibers, with the latter contributing the highest tensile strength. However, the use of polymeric fibers significantly decreases the tensile strength owing to insufficient dispersion and low tensile strength. Scanning electron microscopy images of UHPC with polymeric fibers reveal debonding and surface damage, with potential advantages observed for polypropylene fibers through methods such as surface moisture coating. In conclusion, this paper provides insights into optimizing fiber content and types for UHPC, emphasizing a balance between reduced fiber content and maintained performance. The proposed hybrid reinforcement approach, particularly with short hooked fibers, is promising for practical usability and cost-effectiveness in construction applications. • Addition of hybrid fibers, particularly polymeric fibers, results in a decrease in flowability. • Hybridizing with hooked fibers decreases the fiber content by 0.5 % given similar strength levels. • Long PVA fiber is effective in increasing elastic modulus of UHPC due to limited deformation. • Hybrid use of straight and hooked steel fibers exhibits improved tensile performance of UHPC. • Introduction of PVA and PP fibers causes a decrease in the tensile strength of UHPC. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the variation rule of coarse aggregate and pore structure of shotcrete by adding MWCNTs. In the paper, X-ray computed tomography scans are used to study the coarse aggregate distribution and pore structure of the preparation of shotcrete, high-temperature curing shotcrete and shotcrete with MWCNTs. The distribution pattern of coarse aggregate and pore of shotcrete is obtained. The results show that: the coarse aggregate loss of shotcrete is serious within 30 mm from the wall and the coarse aggregate increases significantly in 30–70 mm. The addition of 0.03% MWCNTs increased the coarse aggregate of shotcrete by 36.63% and the volume of coarse aggregate by 25.64%. The largest increase is in coarse aggregates of 5–7 mm. This show that MWCNTs can improve mortar adhesion and reduce aggregate rebound. The number of shotcrete pores decreases with the increase of pore diameter. The proportion of small pores is up to 85%, the proportion of large pores is only 2%, but the volume of large pores reaches 87%. The addition of 0.03% MWCNTs can reduce the number of small pores in the shotcrete and reduce the mean pore diameter, resulting in a decrease in the porosity of the shotcrete. When the curing temperature is 80℃, the porosity of shotcrete increases, and the pores decrease due to interconnection. The pores around the coarse aggregate account for over 70% of the total porosity, with pores larger than 1 mm accounting for 75%. This paper has a good reference value for the development of shotcrete and the selection of coarse aggregate in the actual working conditions. • The coarse aggregate distribution and pore structure characteristics of shotcrete were revealed. • The influence of MWCNTs on the rebound of shotcrete coarse aggregate was analyzed. • The relationship between pore distribution of shotcrete and coarse aggregate distribution is discussed. [ABSTRACT FROM AUTHOR]

Transparent bamboo (TB) stands as a promising biomass composite material, offering a range of merits including a straightforward preparation, high light transmittance, environmental sustainability, superior mechanical properties, and low thermal conductivity. These characteristics position TB for versatile application spanning energy-efficient building materials, decorative elements, and optoelectronic devices. This comprehensive review aims to elucidate the optical synthesis mechanism of TBs, delving into their functionalization improvement and exploring the potential applications across various domains. This paper serves to furnish readers with a profound understanding of the evolving landscape of TBs and their potential transformative impact. • This paper reviews the synthesis mechanism, preparation process, functional improvement of Transparent bamboo (TB). • The structure, properties and functional characteristics of TB are discussed. • The potential applications of TB in building materials, interior decoration and optoelectronic devices are summarized. • The prospects and challenges for the development of TB are discussed. [ABSTRACT FROM AUTHOR]

Utilizing nano-SiO 2 (NS) to reinforce the old mortar and the weak interfacial transition zone (ITZ) in recycled coarse aggregate (RCA) is a productive approach to enhance the quality of RCA. Throughout this paper, RCA was immersed in NS solutions with different concentrations (2, 5, 10 and 30 wt%). Subsequently, a systematic evaluation of the crushing index and water absorption of the treated NS modified recycled coarse aggregate (SRCA) was conducted. In addition, the calcium hydroxide (CH) content of RCA before and after modification was analyzed by Thermogravimetric and Differential Thermal Analysis (TG-DTA) curves. This study finds that the performance of SRCA modified with 2% concentration achieves comparable modification effects to other concentrations. Additionally, this paper delves into the impact of NS powder on the slump characteristics and compressive strength of concrete. Considering the above research and economic costs, this study adopts 2% concentration of NS for RCA modification and further investigates the stress-strain relationship of NS modified recycled aggregate concrete (SRAC) with various SRCA replacement ratios. Moreover, this paper establishes mesoscopic models of SRAC for various replacement rates and proposes constitutive models corresponding to these rates. The results indicate that when the SRCA replacement rate is within 60%, the stress-strain curve shape of SRAC closely resembles that of natural aggregate concrete (NAC); when the replacement rate exceeds 60%, the descending segment of the SRAC stress-strain curve becomes more precipitous, showing a higher tendency towards fragility in the concrete. ● Nano-SiO 2 can be used to improve the properties of recycled coarse aggregates. ● NS powder affects the slump and compressive strength of recycled concrete. ● As the concentration of NS solution increases, the compressive strength of concrete increases. ● Mesoscopic models of modified recycled concrete were established and constitutive models were proposed. [ABSTRACT FROM AUTHOR]

Since 3D printed concrete has a promising application in engineering, the combination of 3D printing concrete and other building materials has become a hot research topic.This paper investigates the shear properties of 3DPM-NM specimens which use 3D printed mortar (3DPM) as the precast part and normal mortar(NM) as the cast-in-place part. Four different types of interfacial locking design were analyzed in this paper, including L-shaped, C-shaped, S-shaped and K-shaped. The shear damage law of the specimens was analyzed using digital image correlation (DIC) technology. The results show that L-shaped specimens are basically damaged along the shear surface during the loading process. Most of the initial cracks in the C-shaped, S-shaped and K-shaped specimens appeared along the interfacial bonding surface during the loading process. Then, the cracks in the C, S and K-shaped specimens continued to develop along the interfacial bonding surface or spilt through the specimens directly. The results show the shear properties of the C-shaped specimens are similar to those of L-shaped specimens. And the mechanical properties of S-shaped and K-shaped specimens are better than those of L-shaped specimens which increased by 96% (S-shaped), 78% (K-shaped) respectively. The mean slip is increased by 10% in S-shaped specimens and 28% in K-shaped specimens compared with that of L-shaped specimens. According to the AASHTO GSCB INTERIM-2003 specification, the modified formula for the shear bearing capacity of 3DPM-NM specimens is proposed in this study. The calculated resultsare in good agreement with the test results, which theoretically provide guidance for the application of 3DPM, lay the foundation for its feasibility as a structural body of a building. • Specimens with 3D printed mortar (3DPM) as a precast component and normal mortar(NM) as a cast-in-place part were tested. • Comparison of the shear performance of specimens with different types of interfacial locking design were conducted. • Theoretical analysis and modified calculations of shear strength for 3DPM-NM interfacial locking specimens were carried out. [ABSTRACT FROM AUTHOR]

When a slurry shield tunnel traverses through extensive deposits of silty clay stratum, a considerable amount of high-viscosity waste slurry with elevated particle content is inevitably generated. Failure to promptly address this waste slurry could have a severe impact on project progress and the surrounding environment. To address the challenge of rapid dewatering for high-moisture and high clay-content waste slurry, this paper introduces an efficient waste slurry dewatering technique: magnetic flocculation dewatering technology. Additionally, the paper explores avenues for the resource utilization of waste slurry containing magnetic particles Through conducting flocculation settling experiments, a comparative analysis was carried out on the dewatering effects of traditional flocculation and magnetic flocculation technologies. The paper discusses the dewatering mechanism of magnetic flocculation and determines the optimal process conditions for treating waste slurry utilizing magnetic flocculation. The results indicate: (1) The flocculation and dewatering process of waste slurry can be divided into two stages: a rapid flocculation settling stage and a slow consolidation stage, with the rapid flocculation settling stage playing a dominant role. (2) Under magnetic flocculation, the time required for the rapid flocculation settling stage is only 1/3 of that in traditional flocculation, and the slurry dewatering rate is 1.4 times higher than traditional flocculation. (3) The optimal sequence for adding material under magnetic flocculation is to add magnetic powder first and then the flocculant. The optimum dosage of magnetic powder is 1.0 g/L, and the most suitable magnetic field intensity is 92.0 mT. (4) The magnetically flocculated sludge obtained after magnetic flocculation treatment can be utilized for the production of construction bricks that comply with standard specifications. The research findings of this paper provide a basis and guidance for the efficient reduction and resource utilization of waste slurry. • A novel efficient technique for dewatering of waste sludge, known as magnetic flocculation dewatering technology, is introduced. • Comparative analysis between traditional flocculation and magnetic flocculation techniques is conducted to confirm the superior dewatering efficiency of magnetic flocculation. • The mechanism of magnetic flocculation technology in the dewatering process of waste sludge is elucidated, leading to the identification of optimal operational conditions for waste sludge treatment under magnetic flocculation. • A pathway for the resource utilization of waste sludge is proposed, with the feasibility of using waste sludge for the production of construction bricks without firing being validated. [ABSTRACT FROM AUTHOR]

This study proposed a procedure to optimize the mixture proportion of geopolymer using machine learning (ML) and multi-objective optimization (MOO) model, which enhances the compressive strength and minimizes the carbon emission and costs. The experiment was preliminary carried out to analyze the workability, compressive strength, microstructure, and pore characteristics of fly ash/slag-based geopolymer. The results showed that the higher replacement ratio of slag established positive effects on the hardening as well as porosity improvement due to the coexistence of C-S-H and NASH-type binders, especially for a ratio was no more than 60%. Considering the performance of geopolymers is often influenced by multiple factors such as material composition and curing conditions, which could not be solved by traditional methods. A database containing 836 samples was established to analyze the prediction performance of 7 ML models by using Bayesian optimization. The GPR model has good generalization ability, with R 2 being 0.99 (0.99) on the testing set (training set). Furthermore, the reliability of the ML models was evaluated by the tests conducted in this paper. The feature importance analysis utilizing SHAP method indicates that Age, HM, and SS are key parameters influencing the compressive strength of geopolymer. The proposed MOO model can effectively evaluate the trade-offs between compressive strength, carbon emission, and costs, and all Pareto solutions for bi-objective and three-objective provided the optimal mixture schemes. On this basis, the design procedure proposed in this paper can give the scheme of geopolymer materials with different requirements (given mixture scheme and given design strength). [Display omitted] • Working mechanism of different matrix on geopolymer are revealed. • SHAP method can explain the physical mechanism of parameter on the output variable. • Reliability of the intelligent prediction model is validated by experiment. • MOO model can evaluate the relationship between CS, CO 2 and costs of geopolymer. • Procedure of geopolymer mixture schemes with different design strength are proposed. [ABSTRACT FROM AUTHOR]

This paper comprehensively reviews present research on the potential for repurposing primary categories of waste plastics. These include Polyethylene Terephthalate (PETE), High-Density Polyethylene (HDPE), Polyvinyl Chloride (PVC), Low-Density Polyethylene (LDPE), Polypropylene (PP), Polystyrene (PS), and other variants such as Acrylonitrile Butadiene Styrene (ABS), Ethylene Vinyl Acetate (EVA), Polycarbonate (PC), and Polyurethane (PU). The focus is on their use in the construction of bituminous mixes via the dry process method. This method incorporates plastic waste into bituminous mixes by modifying the mixture or replacing aggregates. This practice has consistently demonstrated improvements in pavement performance, including increased stiffness, resistance to rutting, and fatigue. When bituminous mixtures are modified with the mixture modifying approach using low melting point plastics such as LDPE, HDPE, and LLDPE, a significant reduction in OBC is observed. Furthermore, the mixture modification approach has demonstrated higher resistance to moisture damage, rutting, and fatigue damage than the aggregate replacement approach. The potential benefits of using plastics in the bituminous pavement are substantial. This includes a reduction in the amount of waste sent to landfills, a decrease in reliance on finite natural resources, and the expansion of options for constructing bituminous pavements. Economic analyses have shown that using waste plastics can reduce pavement construction costs by 10%, with a minimal probability of leaching. Despite a multifold increase in the emission of greenhouse gases, an overall reduction in environmental impact was observed from the life cycle assessment study. However, the use of PVC and dark-colored plastics is not recommended. Field studies conducted on roads constructed with waste plastic-modified bituminous pavements showed notable improvements. Most of these pavements exhibited higher Pavement Condition Index (PCI) values and lower International Roughness Index (IRI) values than conventional pavements. These findings underscore the superior riding quality and reduced deterioration associated with waste plastic incorporation. Moreover, in-plant production processes, plants require minimal modifications, as existing equipment used for feeding fibers is well-suited for adding plastics into the mixture. In conclusion, further research is essential to fully understand the impact of different types of plastics on pavement performance and to evaluate this process's potential environmental and economic implications. This paper seeks to bridge the gap in the literature by reviewing and discussing the performance of such mixes and constructed pavements in laboratory and field situations. ● The impact of different plastics on mechanical performance of bituminous mix has been reviewed. ● Plastics at OPC improves bituminous mixture's mechanical performance. ● Long term field performance studies have been reviewed. ● Pavements containing waste plastics shows better riding quality and less deterioration. ● Future studies should more focus on environmental assessment. [ABSTRACT FROM AUTHOR]

Over the past year, ChatGPT's initial applications across diverse fields have progressed amid debates on its ethical implications and inherent biases. This paper investigates the comprehension level of ChatGPT 4.0 regarding cementitious composites and initiates preliminary research into its application in cementitious composites，including ordinary Portland cement (OPC) concrete, Engineered Cementitious Composite (ECC), and Ultra-High-Performance Concrete (UHPC). Initially, the study designed forty-five progressively challenging questions to examine the readability and accuracy of ChatGPT's responses related to cementitious composites. Building on this, the research explored the feasibility of utilizing ChatGPT for the identification and analysis of ECC cracks, the design of mix proportions for cementitious composites, and the real-time analysis of carbon emissions. The results demonstrate ChatGPT 4.0's proficiency in acquiring foundational knowledge of cementitious composites, a capability verified through interactive human-computer modalities for analysing crack quantity and width, formulating preliminary material compositions, and providing instantaneous feedback on carbon emissions. However, the study also uncovers ChatGPT 4.0's limitations in understanding the complex design mathematics and mechanics underlying cementitious composites, as well as its inadequate ability to synthesise and integrate interdisciplinary knowledge, occasionally leading to arbitrary and forced responses. These findings underscore the need for further enhancements in algorithmic sophistication and database comprehensiveness. The paper concludes by projecting the future applicability of ChatGPT in the cementitious composites sector, highlighting its initial contributions while delineating avenues for subsequent research and development. • The understanding of ChatGPT on cementitious composites was investigated. • The preliminary application study of ChatGPT 4.0 was conducted. • The future application prospects of ChatGPT were anticipated. [ABSTRACT FROM AUTHOR]

All-Bamboo Aggregate Concrete (BAC) is a type of cement concrete material where all coarse aggregates are made of bamboo aggregate, a plant material that requires necessary measures to avoid or slow down its degradation in alkaline and natural environments. This paper enhances the durability of BAC materials through the treatment of bamboo aggregate with ACQ-polyacrylate (AP method). Initially, the study explores the impact of polyacrylate dilution concentration on the compressive strength and coating thickness of BAC, and based on a reasonable modification process, conducts freeze-thaw cycles, salt solution immersion, accelerated wet-dry aging, and long-term natural environment tests to assess the durability of BAC materials. The results show that a polyacrylate solution with a dilution ratio of 1:5 can form a coating thickness of 23.8μm, performing better in various durability evaluations. After 25 freeze-thaw cycles, the BAC material's loss rate of compressive strength is lower than that of Ordinary Concrete (OC). Compared with OC, BAC materials are more susceptible to salt damage after salt solution immersion. The compressive strength loss rate under 180 days of natural environment exposure is comparable to that in 10 cycles of accelerated wet-dry aging, 28 days of salt solution immersion, and 10–15 freeze-thaw cycle tests, recommending the use of freeze-thaw cycle tests for evaluating the durability of BAC materials from an experimental efficiency perspective. By exploring the durability of BAC materials, this paper provides an innovative solution in the field of construction materials, promoting the transition of the construction industry towards sustainable development. It emphasizes the feasibility and effectiveness of improving the performance of bamboo-based materials through surface treatment technology, offering a valid reference for developing more environmentally friendly and high-performance new materials in the future. • BAC materials show lower durability than traditional concrete. • Polyacrylate solution can enhance BAC durability. • Polyacrylate solution can enhance BAC durability. • Future research should optimize polyacrylate modification. [ABSTRACT FROM AUTHOR]

Building precise machine learning and deep learning models has traditionally required a combination of mathematical skills and hands-on experience to meticulously adjust hyperparameters that significantly impact the learning process. As datasets continue to expand across various engineering domains, researchers increasingly turn to machine learning methods to uncover hidden insights that may elude classic regression techniques. This surge in adoption raises concerns about the adequacy of resultant meta-models and the interpretation of findings. In response to these challenges, automated machine learning (AutoML) emerges as a promising solution, aiming to construct machine learning models with minimal intervention or guidance from human experts. This paper benchmarks AutoML solutions by providing an overview of their principles and applying them to predict the most important mechanical properties of different concrete datasets, i.e., compressive strength. Nine datasets from various concrete types, sample sizes, and features are utilized, with a detailed discussion on the benchmark dataset from high-performance concrete, applying best practices to the other eight datasets. For each case, the importance of hyperparameter tuning is discussed, alongside the ensemble and stacking models. Tree-based models are employed for each dataset to develop SHAP plots, interpret results, and understand the contribution of each component in the mix design to the overall strength of the concrete. This paper further explores three unique aspects of benchmarking AutoML in material science: (1) "reliability" by contrasting the benchmark dataset's error metric with literature collected over the past 20 years, (2) "uncertainty" by quantifying the variability in the mean and standard deviation of the error metric from different datasets and its correlation with the sample-to-feature ratio, and (3) "dilemma" by discussing the shortcomings of AutoML in specific concrete datasets. • The first comprehensive application of AutoML is presented in the concrete regression model. • Nine different concrete datasets are compared in terms of compressive strength. • AutoML's reliability, and dilemmas are evaluated in predicting concrete strength. • A benchmark problem is discussed to quantify the AutoML uncertainty in material science. • Explainable machine learning is used to identify the key contributing factors in f' c. [ABSTRACT FROM AUTHOR]

This paper not only studies the influence of fiber content on the mechanical properties of steel fiber ultra-high performance concrete (SFRUHPC), but also conducts high-speed impact tests and simulations on high-volume fiber targets with varying thicknesses to evaluate the damage characteristics of the SFRUHPC targets, such as residual velocity and penetration depth of the projectile. The results indicate that compared with ordinary concrete and low fiber content targets, the flexural strength and compressive strength of the target incorporated with 7% steel fiber reach the maximum values of 87.9 MPa and 362.9 MPa, respectively, which are significantly improved. On the other hand, the 7% steel fiber reinforced target demonstrates excellent anti-penetration performance which is evidenced by a 51.9% lower residual velocity compared to ordinary concrete targets in thin target tests, as well as a 37.4% reduction in penetration depth in thick target tests. Additionally, the rebound phenomenon of the projectile is observed during the tests. Furthermore, the three-dimensional mesoscopic numerical model established exhibits a good correlation with the experimental results. Finally, the model adopted in this paper can better predict the residual velocity and depth of penetration of the projectile. • The anti-penetration performance of three types of targets incorporating high content steel fibers were evaluated. • The high content steel fibers attribute to the better penetration resistance. • The phenomenon of projectile rebound is observed in a thick target with a steel fiber content of 7%. • The established three-dimensional mesoscopic numerical model aligns well with the experimental data. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the microstructure of high-viscosity modified asphalt binder (HVA) containing high-content polymers and its effect on fatigue performance, as well as the applicability of different analytical methods and failure criteria of linear amplitude sweep (LAS) test to HVA. In this paper, two types of HVAs with different polymer contents, a commercial HVA, a conventional polymer-modified asphalt binder, and a base asphalt binder were first prepared or selected. Fluorescence microscopy tests, time sweep tests, and LAS fatigue tests were then performed on these binders. Finally, the fatigue properties of the different binders were analyzed in depth using different analytical methods and failure criteria. The results show that the polymers in HVA crosslink with each other to form a strong cross-linking structure, and the phase inversion of the polymers renders them into a continuous phase, which significantly improves the fatigue damage resistance of the HVA; moreover, the evolutions of stress with shear strain for the fatigue process of HVAs is related to the polymer network. Besides, the two-dimensional damage characteristic curve (DCC) cannot accurately reflect the evolution of the fatigue performance of HVA, and this paper suggests the use of a three-dimensional DCC curve with strain information. Furthermore, the 35% reduction in C 0 in the dissipative energy method is not a suitable failure criterion, a more accurate fatigue performance ranking can be obtained by using the yield stress as the failure criterion. Although the fatigue resistance of HVA after yield stress is theoretically considered using the pseudo-strain energy approach, HVA does not show a peak of stored pseudo-strain energy even when the strain is increased to 60% in the LAS test. Therefore, the maximum strain value (30%) in the standard LAS test is not sufficient in characterizing high-polymer HVAs because there is not enough fatigue accumulation of HVAs in this range, consequently, the maximum shear strain parameter in the LAS experiment needs to be reconsidered. • Polymer morphology and its crosslinking networks in HVA with high-content polymers were analyzed. • The fatigue properties of HVAs based on LAS test and different analytical methods are compared. • The fatigue crack length and its evolution of HVA are characterized. • The deficiencies of the LAS test to evaluate the fatigue resistance of HVA and suggestions for modifications are presented. [ABSTRACT FROM AUTHOR]

This review paper presents a comparative evaluation of polymer, bacterial-based, alkali-activated, and geopolymer binders in regard to their production methods, mechanical properties, their environmental/life cycle assessment (LCA), and durability when exposed to deteriorating cycles (such as sulfates, acids, and high temperatures). The significance of this study is to compare the results of over 400 journal papers, which present an in-depth analysis of fresh and hardened state properties of various binders that are advocated in the literature. Historically, Portland cement is generally considered a binder that plays a major role in any cementitious composites because of its high availability, and relatively inexpensive cost. Despite its significant benefits, it is known that the manufacturing process of Portland cement is energy and carbon intensive, and the resulted material often has shortcomings when exposed to deteriorating causes such as sulfates, acids, and high temperatures. However, recent movement toward net-zero as well as ultra-high-performance practices has increased the need for a more sustainable and durable binding system. Based on the result of this paper, each binder presents specific advantages when compared to Portland cement for specific applications that can be a better choice for their ultra-high capabilities and ecological properties. This includes the significantly better performance of alkali-activated binders (specifically geopolymers), under high temperatures, or very rapid strength gain of polymer (e.g., epoxy, polyester, and vinyl ester) binders, making them great alternatives to Portland cement, for rapid repair and rehabilitation purposes. Similarly, bacterial concrete also have certain capabilities such as long term durability and the potential for a continued self-repair or self-healing. In terms of environmental impacts, however, polymer binders are heavily depedant on their source of energy (e.g., petroleum vs. bio-based resins) while alkali-activated concretes and geopolymers have activators' large contributions to overall LCA impact categories. For bacterial binders, the used urea and nutrition can play a key role in their LCA results. Finally, based on the highlighted capabilities of each binder, recommendations on performance-based or hybrid design methods and specifications for an optimized system are also provided. Novel areas in polymer, bacterial-based, alkali-activated, and geopolymer binders are also included. • A comparative analysis of various binding systems are provided. • Mechanical, Durability, and Ecological Properties vary significantly across binders. • Concentration, surface area, temp., and catalysts play key role in each binder. • Unique advantages and shortcomings of each binder is discussed. [ABSTRACT FROM AUTHOR]

Shape memory alloy (SMA) is an innovative intelligent material, capable of restoring its shape before deformation upon reaching the critical activation temperature. This property promotes its promising applications in civil engineering. This paper proposes a novel reinforcement method and aims to investigate the reinforcing effect of iron-based shape memory alloy (Fe-SMA) plates on prestressed concrete (PC) beams through four-point bending tests on one reference beam without reinforcement and three Fe-SMA reinforced beams, as well as with three beams reinforced by carbon fiber-reinforced polymer (CFRP). The results show that Fe-SMA can effectively reduce concrete cracks, and improve stiffness and characteristic loads of beams without negative effects. Under the same loading conditions, new cracks of Fe-SMA reinforced beams were relatively fewer than those of CFRP reinforced beams. Besides, Fe-SMA exhibited superior performance when utilizing the same cross-sectional reinforcement material to enhance the bending capacity of beam, and proved more advantageous for improving stiffness and characteristic loads of beam under the identical initial tensile force. Furthermore, the reinforcing effectiveness of Fe-SMA positively correlates with the cross-sectional area (thickness) and recovery stress (pre-stretch level and activation temperature) of Fe-SMA. Increasing the thickness of Fe-SMA plates by 100%, while maintaining other parameters constant, resulted in a 33% increase in cracking load. Similarly, elevating the recovery stress from 314 MPa to 340 MPa led to a 12.5% rise in cracking load. This paper investigates the reinforcement effect of Fe-SMA plates on PC beams, and provides a reference for the application of Fe-SMA in PC beam reinforcement, laying a foundation for promoting the utilization of Fe-SMA in civil engineering. • A novel reinforcement system to strengthen PC beams employing Fe-SMA plates was proposed. • The effect of Fe-SMA plates on PC beams through four-point bending tests was compared with CFRP tendons. • Fe-SMA was more effective than CFRP in enhancing the bending capacity of PC beams. • The reinforcing effectiveness of Fe-SMA positively correlates with cross-sectional area and recovery stress. [ABSTRACT FROM AUTHOR]

Surface (microscale) roughness of coarse aggregates influence the cement suspension' viscosity and the interfacial bonding strength of concrete, but its characterization method is not consolidated and still a research challenge. 3D scanner determines accurately the shape, volume, but it is incapable of describing the roughness at microscale. Roughness at microscale (surface index – cm2/cm2) can be measured accurately using interferometry, but it cannot describe shape and volume of the particles. Once the volume of aggregate particles may vary 200% and it seems crucial to establish the (micro)roughness per volume (cm2/cm3) to better understand the effects in the properties of cementitious materials. This paper presents a method of obtaining volumetric surface area of coarse aggregates at micrometric scale by joining (cm2/cm3) both techniques. Three types of aggregates were assessed: gneiss, low-grade meta-carbonate (dolomite) and quartzite (gravel), with one hundred particles in the size range of 4.75 mm to 37.5 mm. For coarse aggregates, the larger the particles, the more of their surface area will be influenced by (mesoscale) shape and less by surface (microscale) roughness. However, the smaller the particles, SI index will differ considerably. The surface area determined by the method proposed in this paper provides a good correlation with the methylene blue method. • New method to determine volumetric surface area (VSA) of aggregates. • Light white interferometry and 3D scanning methods combined. • Shape and roughness (multiscale) morphological descriptors discussed. [ABSTRACT FROM AUTHOR]

In this paper, a thermo-mechanical sequential coupling mesoscopic simulation method was established and verified, which considered the interaction between steel tube and meso-components of concrete due to the difference in thermal parameters, as well as the low-temperature effect on mechanical parameters. On the basis of heat conduction analysis, the damage evolution and failure mechanism of CFST column under axial compression were subsequently revealed, and the effects of low temperature (20, −30, −60 and −80 °C), cross-section size (160, 320, 480 and 640 mm), width-thickness ratio (27, 36, 53 and 107) and cross-section shape (square and circular) on axial compression performance and the corresponding size effect of CFST columns were quantitatively analysed. Research results show that the low-temperature action can enhance the nominal peak strength and residual strength of CFST column, but weaken the ductility. As the cross-section size increases from 160 to 640 mm, all the nominal peak strength, nominal residual strength and peak strain of circular CFST column decrease with the maximum reductions of 16.2, 28.7 and 16.9%, respectively. Besides, the low-temperature action can enhance the size effect on nominal peak strength of CFST column with the maximum increase of 68.8%. Whether at ambient or low temperature, the size effect on nominal peak strength of square column is stronger than that of circular one. The size effect behaviour on axial compressive peak strength at various temperatures can be also well described by the previous proposed prediction formula. The research results of this paper can provide reference for the engineering application of large-sized CFST columns in the extreme low-temperature environment. • The thermo-mechanical sequential coupling method at low temperature was developed. • The effect of low temperature, width-thickness ratio, cross-section size and cross-section shape were considered. • The mechanical properties and corresponding size effect of CFST columns at low temperature were quantitatively analyzed. [ABSTRACT FROM AUTHOR]

In this paper an overview is presented on the use of diatomaceous earth (DE) as a partial substitute for binder and fine aggregate in mortars. For this purpose, this paper was divided into two sections. In the first one, concepts related to physical, chemical and microstructural properties of DE, as well as results of previous studies about its reactivity used in different construction materials (cement, concrete, mortar, bricks, phase change materials etc.) were summarized and discussed. In the next section, the effects of using DE on the fresh, hardening and durability properties of cement and lime-based mortars were discussed. In general, the results suggest that increasing DE content may reduce mortar performance due to the high porosity of its particles. However, this deficiency was observed for DE contents higher than 20%, which, however, can be compensated for by using superplasticizer additives or by volumetric dosage instead of by weight one. This critical value of up to 20% of DE was calculated using T2 statistical on the scores of principal components analysis obtained from the results collected from publish manuscripts. Nevertheless, the results of this review research may contribute to provide information on an under-explored alternative source of supplementary cementitious materials (SCMs) and therefore help mitigate the negative effects generated by the cement industry and assist in the production of mortars with a lower carbon footprint that can play an important role in the thermal behavior of buildings. • State of the art systematic review of diatomaceous earth (DE) for mortar production. • Statistical analysis of the mechanical properties of mortar with DE. • Understanding the effects of DE on properties of mortars. • When up to 20% DE is used, the mechanical behavior of mortars can be improved. • Paths for the development of new studies on mortars incorporating DE are shown. [ABSTRACT FROM AUTHOR]

To improve the fatigue behaviour of the concrete, this paper explored a potential innovative method: the joint addition of expansive agents (EA) and glass fibres (GF). It was envisaged that the addition of EA reduced additional defects caused by the addition of GF to the concrete, while the compressive prestress caused by EA enhanced the bonding between GF and the concrete, thereby improving the fatigue behaviour of the concrete. The test results indicated that the synergistic effect of EA and GF effectively improved the static bending strength, fatigue life, and deformation performance of the concrete. The synergistic effect of EA and GF on the fatigue life of the concrete was revealed qualitatively and quantitatively. The synergistic effect was further demonstrated from perspectives of the fatigue deformation and fatigue stiffness. Furthermore, P - S - N curves of EA and GF reinforced concrete were established, and the fatigue ultimate strength and conditional fatigue ultimate strength were provided as a design basis. This paper recommended adding an appropriate amount of EA to glass fibre reinforced concrete to achieve better concrete properties. • Joint addition of EA and Gf was a potential method for improving concrete. • Bending tests were used to elucidate fatigue bending performance of concrete. • Synergistic effect of EA and GF on fatigue performance of concrete was reveal. • Using two-paramater Weibull distribution, P - S - N curves were established. [ABSTRACT FROM AUTHOR]

Freeze-thaw modification is a novel method that improves recycled aggregates by utilizing the expansion of pore water during phase transitions. However, there is still a lack of theoretical analysis regarding each component in recycled aggregates during freeze-thaw. In this paper, we introduce the parameter of pore radius to transform the traditional 2D phase diagram into a 3D phase diagram of pore water. This transformation makes the phase transition conditions of pore water more clear to understand. It is then combined with the pore size distribution of each component in recycled aggregate to calculate the ice content and freezing pressure. To achieve a more intuitive evaluation of frost susceptibility, this paper establishes a frost vulnerability index (FVI). Based on the FVI curves of different rocks, their frost resistance is categorized into three levels. Finally, according to the FVI of recycled aggregates with diverse material properties, some recommendations are provided for the engineering application of freeze-thaw modification. • By introducing the pore radius, the 2D phase diagram of water is transformed into a 3D diagram. • FVI has been established to assess the susceptibility of different materials to freeze-thaw damage. • The commen natural rocks are classified into three levels based on their frost resistance. • The necessity of thermo-drying is verified through analysis. • Theoretical analysis is conducted on the saturation level required and during the vacuum saturation. [ABSTRACT FROM AUTHOR]

Cement-based grout is widely used for backfill grouting in shield tunnels. However, traditional cement-based grout is prone to segregation, layering, and low retention rates, which leads to a not ideal filling effect of the shield tail gap. This paper innovatively uses three industrial solid wastes as supplementary cementitious materials (SCMs), to replace cement in the composition of backfill grouting materials: silica fume (SF); ground granulated blast-furnace slag (GGBS); and fly ash (FA). Taking the content of SF, GGBS and FA as variables, and fluidity, bleeding rate, concretion rate, setting time and compressive strength as response targets, a regression model was established by the Response Surface Method to explore the effects of the different factors and their interactions on the responses. Results show that the SF content has a significant effect on the characteristics of the grout; the GGBS content is positively correlated with the setting time and compressive strength; the content of FA has a significant effect on the hardening characteristics of the grout, being positively correlated with the setting time and negatively correlated with the compressive strength. Additionally, combined with the desirability function, multi-objective optimization was performed and an optimized mix ratio of SF=5.3 wt%, GGBS=9.0 wt%, FA=60.0 wt%, PC=25.7 wt%, was obtained. The response values of the grout for this composition were verified by experiments and the errors are less than 10%. Compared with the traditional cement-based grout, the grout with the optimized composition uses SCMs to reduce the PC content and significantly improve the grout stability and later strength, indicating that the SCMs used in this paper are effective and the RSM has high accuracy and good reliability. Consequently, RSM can be used to analyze, predict and optimize the mixing ratio of backfill grout in shield tunnelling. • Three types of solid waste were innovatively used to create optimized backfilling grouting materials for shield tunneling. • The interactions among various influencing factors have been elucidated through the implementation of Response Surface Method. • The developed backfill grouting materials have a good performance, environmental friendliness and cost-effectiveness. [ABSTRACT FROM AUTHOR]

Polymer grouting materials are widely used in the trenchless rehabilitation of underground pipe networks and infrastructures. Numerous publications focused on the mechanical properties of the composite's interface, which is critical for the stability and strength of composite structures. However, there is a scarcity of reports on the microscopic characterization and interactive mechanisms of polymer-bentonite system. In this paper, a microscopic combination interface model of polymer-bentonite was constructed based on the molecular dynamics simulation method, and the interfacial shear mechanical properties were investigated under different working conditions. The results show that the shear strength of the polymer-bentonite interface increases with the increase of shear rate and normal stress, which is consistent with the experimental results. The application of normal stress leads to a decrease in the van der Waals gap at the interface and an increase in the density of the dense interface, thus increasing the shear strength of the interface. In addition, the shear strength of the interface in the presence of defects on the surface of the clay crystals is determined by the nonbonding interaction potential energy together with the roughness. As the shear rate increases, shear thinning occurs at the polymer-bentonite interface, and the effect of roughness on the interfacial shear properties gradually decreases. This paper reveals the mechanical properties of the polymer-bentonite interface under the influence of different factors from a microscopic point of view. • Micromechanical characterization of bentonite-polymer interfaces using molecular dynamics simulations. • Pull-out simulations of the interface were performed considering the effects of pull-out rate, normal stress, clay crystal defects, and different interface types. • Mechanism of synergistic enhancement of interfacial properties by roughness and non-bonded interaction potentials revealed. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive review of calcium sulfate whiskers (CSW), focusing on their synthesis methods, morphological characteristics, and diverse applications across industries. Whiskers, known for their specific length-to-diameter ratio and ordered atomic structure, offer exceptional physical and mechanical properties, making them valuable reinforcements for various materials. Through a bibliometric analysis, a comprehensive overview of the existing research landscape within this field is provided, offering valuable insights into potential future research directions, and identifying promising avenues for further investigation The paper highlights the significance of controlling reaction parameters to achieve high-quality whiskers with desirable morphologies. Furthermore, the crystal symmetry and composition of calcium sulfate whiskers play crucial roles in determining the thermal behavior and performance of CSW. The multifaceted applications of CSW are extensively discussed, ranging from enhancing the mechanical properties of plastics, ceramics, and rubber to improving friction materials, paper production, and environmental filter materials. This review underscores the growing importance of CSW as versatile reinforcements and highlights the need for further research to optimize synthesis techniques and explore novel applications in emerging fields. [Display omitted] • Innovative applications of Calcium sulphate whiskers. • Enhancement in Mechanical properties. • Slender needle like structures. • Acts as pore filler. • Atmospheric and hydrothermal acidification synthesis of CSW. [ABSTRACT FROM AUTHOR]

The development of ultra-high performance concrete (UHPC) with lower carbon emission has conducted by many researchers. However, there is a lack of quantitative comparison of carbon reduction efficiency, such as carbon emission and energy consumption values, of UHPC materials with various components. This paper reviews the trends toward lower-carbon UHPC based on Life Cycle Assessment related to the used materials, especially different binders, aggregates, and steel fibers. The environmental indicators, including embodied carbon emissions (EC), embodied energy consumption (EE), and embodied CO 2 index (CI) value, of UHPC mixtures in published paper are discussed. Since compressive strength is an important indicator, the minimum value of compressive strength of UHPC should be greater than 120 MPa in the assessment process. Moreover, the effectiveness of using various low-carbon alternatives is discussed and then ranked according to the reduction degrees of EC and EE. Results found that ultra-high performance geopolymer concrete (UHPGC) shows the lowest EC and EE and the highest CI. This indicates that UHPGC has decreased carbon emissions without compromising compressive strength. The use of supplementary cementitious materials and recycled powder obtained from waste aggregates to substitute cement is another effective way to reduce EE and EC. However, using waste aggregates or waste fibers to replace conventional aggregates or steel fibers is less efficient than cement replacement with supplementary cementitious materials (SCMs). Especially, the use of waste aggregate leads to negligible reductions in EC and EE. The study seeks to find out the most promising route for low-carbon UHPC in the circular economy through identifying low-carbon alternatives, which has great significance in designing low-carbon UHPC. • Multiple strategies to develop lower-carbon UHPC are reviewed. • The environmental impacts of different UHPC are systematically calculated based on LCA at a material level. • These strategies are discussed and ranked based on performances and environmental impacts. • The most effective strategy for developing lower-carbon UHPC is indicated. • Perspective for how to develop lower-carbon UHPC is given. [ABSTRACT FROM AUTHOR]

Recycling of UV-aged asphalt has been a hot research issue. In this paper, waste cooking oil, plasticizer, toughener, and petroleum resin were used as raw materials for asphalt rejuvenator. This paper explores the effect of regeneration conditions on the regeneration effect of UV-aged asphalt binders through high-temperature rheology and chemical compositions. The paper also attempts to reveal the regeneration mechanism of asphalt binder regeneration using waste cooking oil. Dynamic shear rheology (DSR) and fourier transform infrared (FTIR) spectroscopy assess high-temperature rheological properties and chemical compositions. The Pearson correlation coefficient relates the rheological parameters to the chemical microstructure. And the functional relationship between carbonyl-corrected peak area and aging factor Ai of recycled asphalt and high temperature rheological parameters were established. Molecular simulation investigates WCO-recycled asphalt binder micro-morphology and adsorption mechanisms. The results showed that significant changes in the carbonyl and sulfoxide peak areas affected the high-temperature rheological properties. Regeneration conditions significantly affect asphalt regeneration effectiveness. WCO reduces C O and S O groups, crucial in asphalt viscoelastic behavior. Molecular interaction analysis reveals WCO's regenerative mechanism. This work emphasizes integrating molecular structure, chemical composition, and macroscopic properties in asphalt binder research, providing insights for sustainable pavement practices. • The content of C=O and S=O are the main factors determining the recycling effect of WCO recycled asphalt. • WCO rejuvenator changes the molecular structure of aged asphalt. • The -OH group of WCO increases the interaction between WCO molecules and aged asphalt molecules. [ABSTRACT FROM AUTHOR]

In this paper, the hydration process of cement paste with hydrophilic nano-TiO 2 particles was studied by microcalorimeter and electrochemical impedance spectroscopy, and the hydration mechanism was explored based on Krstulovic-Dabic kinetic model. Meanwhile, the photocatalytic activity and antibacterial properties of TiO 2 -modified cement pastes were investigated by ultraviolet spectrophotometer and enzyme activity analyzer respectively. The results show that TiO 2 nanoparticles can promote the hydration rate of cement in the acceleration stage, increase the cumulative heat release of early hydration, but delay the hydration process in the later stage. The Krstulovic-Dabic model can effectively simulate the hydration process of cement pastes with TiO 2. Nano-TiO 2 helps to increase the hydration rate of the crystal nucleation and growth process (NG) and shorten the duration of phase boundary reaction process (I), but has a negative impact on ion diffusion process (D). The functional relationship between the resistivity ρ of TiO 2 cement-based composites and the hydration kinetic parameters was established: ρ (t) = − 1 k 1 ln [ β 1 + t 50 t − t 0 ].The degree of hydration of cement can be assessed by electrochemical in-situ non-destructive monitoring of the sample. In addition, the photocatalytic oxidation rate of TiO 2 -modified cement-based composites was up to 69.4%. Compared with the control sample without nano TiO 2 , the antibacterial ability was increased by 72.35%. In this paper, nano-TiO 2 was applied to cement system, which provided a new idea for the preparation and application of photocatalytic antibacterial cement-based composites. • The hydration mechanism of cement pastes with nano-TiO 2 has been explored by EIS and kinetic model. • The equation between cumulative heat release and resistivity is: Q (t) = k 1 e k 2 ρ (t) . • The cement pastes with TiO 2 have excellent photocatalytic activity and antimicrobial properties. [ABSTRACT FROM AUTHOR]

High-strength steel reinforced concrete (HSRC) columns configured with T63E/E/G rebar (whose yield strength is 630 MPa) have significant advantages such as less steel consumption and higher load carrying capacity. However, the compressive strength level of T63E/E/G rebar in HSRC columns under eccentric compression with a large eccentricity (LEC-HSRC) and the eccentric load carrying capacity calculation model is not precisely determined yet. In this paper, 11 LEC-HSRC columns were tested, then the test results and sectional stress state are discussed in depth. The results show that the compressive strength of T63E/E/G rebar could be fully utilized in LEC-HSRC columns, thus the compressive strength design value of T63E/E/G rebar in Technical specification for application of new heat-treatment high-strength ribbed bar in concrete structures DBJ 61/T 157–2019 was revised to 545 MPa accordingly, to the same level as the tensile strength design value. It's conservative to calculate the eccentric load carrying capacity of LEC-HSRC columns according to Code for design of concrete structures GB 50010–2010. A new eccentric load carrying capacity calculation model, which satisfies both the static equilibrium and strain compatibility condition, was proposed based on stirrup confined concrete constitutive relation, and it has higher accuracy compared with currently used models. The assumption that the strain at the edge of the compression zone of core concrete reaches the peak under ultimate load can suitably calculate the compressive stress of T63E/E/G rebars in LEC-HSRC columns. This paper offers experiment and theory support for the revision of DBJ 61/T 157–2019 and the engineering application of T63E/E/G rebar in China. • T63E/E/G high-strength rebar's compressive strength level in LEC-HSRC columns is experimentally and theoretically studied. • An eccentric load carrying capacity calculation mode based on the stirrup confined concrete constitutive relation is proposed. • The compressive strength design value of T63E/E/G rebar is revised from 435 MPa to 545 MPa in standard DBJ 61/T 157-2019. • The strain at the edge of the compression zone of core concrete reaches the peak under ultimate load. [ABSTRACT FROM AUTHOR]

Geopolymer concrete is a sustainable replacement to the Ordinary Portland Cement (OPC) concrete as it mitigates some of the associated problems of OPC manufacturing such as greenhouse gas emission and natural resource depletion. There has been significant recent research in the design of fly ash-based geopolymer concrete using advanced machine learning techniques which can address some of the problems with classical mix design approaches. However, practical application of geopolymer concrete is limited due to lack of standard mix design procedure. This comprehensive review summarizes the current literature on machine learning methodologies to predict the compressive strength of fly ash-based geopolymer concrete. Firstly, the input parameters used for the machine learning model development are categorized based on feature selection or feature extraction. Secondly, available machine learning approaches are categorized based on analysis methods namely, nonlinear regression, ensemble learning, and evolutionary programming. The effect of hyperparameters on the individual model performance, and model comparison based on the prediction performance are also discussed to identify potentially more suitable model type and hyper parameter ranges. Further, the paper discusses the input variable's sensitivity towards the model performance which provides guidance towards future model developments. Overall, this paper will provide an understanding of the current state of machine learning approaches to predict the compressive strength of geopolymer concrete and the gaps in research for the development of models and achieving the required performance. Hence, the summarized knowledge will be highly beneficial to design prospective research towards sustainable cement-free concrete using fly ash. • Artificial neural networks (ANN) predict geopolymer concrete strength well, offering reliable forecasts for new data. • Support vector machines and random forests offer ANN- like performance, serving as alternatives in machine learning (ML). • The success of ML model relies on proper selection of inputs and tuning hyperparameters for optimal performance. • The chemical, physical, and mineralogical characteristics of fly ash emerge as pivotal input variables in ML models. • Validating models through laboratory experiments is imperative, ensuring generalization for real-world applications. [ABSTRACT FROM AUTHOR]

In this paper, data from the PURWheel-G2 , a rubber tire wheel tracker, was utilized alongside several techniques to better understand isolation of the effects of moisture on asphalt rutting. Techniques commonly used to interpret wheel tracking data, particularly to evaluate moisture damage, were summarized and used to evaluate over 150 PURWheel-G2 tests where wet and dry pairs of tests were conducted to directly isolate the effect of moisture on rutting. Among all the available wheel tracking analysis techniques and models for moisture evaluation, there lacks a consensus approach, and available approaches vary widely highlighting the need for a standard test method. The rubber tire wheel tracker presented in this paper aims to take a step towards developing test protocols to isolate moisture damage. The ability to measure the effects of moisture on rutting is a feature that other existing wheel tracking methods cannot do on their own. • Rubber-tire wheel tracker tests were evaluated to isolate the effects of moisture. • Over 150 PURWheel-G2 tests in wet and dry conditions were conducted. • There is no consensus on how to analyze wheel tracking data for moisture evaluation.. [ABSTRACT FROM AUTHOR]

The increasing volume of waste rubber generated from end-of-life tyres has raised significant concerns regarding the safe and sustainable recycling and reuse of this material. A viable solution is to incorporate waste rubber into asphalt mixtures, which contributes to recycling waste tyres and promotes the sustainability and resilience of pavement infrastructure. In recent years, Crumb Rubber-Stone Mastic Asphalt (CR-SMA) mixtures have received considerable attention due to their remarkable performance. However, the feasibility of implementing CR-SMA in the field on a large scale requires further investigation. This paper aims to evaluate this matter by reviewing the mix design practices of CR-SMA, assessing the performance characteristics of CR-SMA, and identifying gaps and potential areas for improvement. The gaps related to various factors like aggregate gradation, compaction technique, processing temperature, CR grains size and their concentration, and binder content have been identified and discussed in the paper. In addition, the key performance characteristics of CR-SMA mixtures, including binder drain-down, moisture susceptibility, permanent deformation, and fatigue cracking, are evaluated. • Review history of waste tyre rubber in bituminous mixtures, tracing its evolution. • Explore the mix design practices of Crumb Rubber-Stone Mastic Asphalt (CR-SMA). • Investigate the mechanical properties and performance of CR-SMA. • Discuss the influence of CR characteristics on SMA performance. • Critically highlight CR-SMA research gaps, providing direction for future studies. [ABSTRACT FROM AUTHOR]

Fully utilizing regional resources such as marine sand, coral, and desert sand, along with a diverse range of solid wastes from industries, agriculture, and urban areas, not only effectively reduces the costs and carbon footprint of construction activities but also contributes to achieving sustainable development in the building sector. Despite earlier studies focusing on the feasibility of solid waste as lightweight aggregates, the comprehensive evaluation of the performance of alternative aggregates in such innovative materials as geopolymers and ultra-high-performance concrete remains significantly limited amid their rapid development. Therefore, this paper concentrates on a thorough exploration of regional sand and gravel resources, as well as efficient and value-added approaches to incorporating solid wastes from industries, agriculture, and urban areas as alternative aggregates in construction. It provides a comprehensive review of the physical properties of alternative aggregates and their impacts on the workability, mechanical properties, and durability of concrete. Additionally, the paper offers a detailed assessment of the production processes and performance of sintered and cold-bonded artificial aggregates. This research provides valuable insights for researchers and practitioners in the fields of construction, sustainable waste management, resource conservation, and recycling. • Regional resources, industrial and agricultural and urban solid wastes are used as clean aggregates. • Potential legal challenges to the use of clean aggregates are revealed. • Reviewed the modification methods of granular solid waste. • Reviewed artificial agglomeration techniques and potential challenges for powdered solid waste. [ABSTRACT FROM AUTHOR]

In this paper, the central pull-out tests were carried out on shape memory alloy fiber-reinforced concrete (SMA-FRC) under monotonic load. The failure modes and failure mechanisms of the specimens were observed and analyzed, and the bond strength and slip distance were measured. The effects of different influencing factors on the mechanical behavior of bond-slip were investigated, and the bond-slip constitutive model of shape memory alloy (SMA) bar and SMA-FRC was proposed. The test results indicated that the ultimate bond strength between SMA bars and SMA-FRC gradually increased with the addition of SMA fiber, the reduction of SMA bar diameter, the decrease of anchorage length, and the lowering of temperature within a certain range. In this paper, based on the theoretical analysis of the test data, a reasonable bond-slip constitutive model was established, which can better predict the test results. • The effect of various factors on the bonding properties is analyzed and the best combination of factors is obtained. • The influencing factors were analyzed by response surface method, and the optimal solution of bond strength was obtained. • A new bond-slip constitutive model is proposed, which has wide applicability and accuracy. [ABSTRACT FROM AUTHOR]

The effects of ageing on pavement performance are significant, particularly in terms of fatigue cracking. South Africa has the 10th longest road network in the world, requiring innovative approaches to road construction due to severe budget constraints. Innovative solutions such as thin asphalt concrete layers for surfacing, result in unique ageing rates of the layers, which, in general, have a higher incidence of fatigue cracking than, for example, thicker asphalt concrete layers used in other parts of the world. The objective of this paper is to evaluate how ageing mechanisms affect various asphalt binder properties, and whether they affect them to the same extent or not. Furthermore, the objective of the paper is also to determine the accuracy of the Rolling Thin Film Oven Test (RTFOT) in simulating short-term ageing in the field. The RTFOT provides a relatively good indication of short-term ageing, according to this multi-decade ageing study, and the effect on the asphalt binder properties used as ageing indices depends on the specific property chosen for comparison before and after ageing. • From 2001 to 2012, the prevalent surfacing in South Africa was a dense-graded asphalt mix with 50/70-grade asphalt binder. • Asphalt binders were consistent over 2001 to 2012, originating from four South African refineries. • A short-term ageing method in the laboratory cannot emulate the reaction kinetics during manufacturing and placement. • Binder properties such as penetration and softening are affected to different extents in an oxidation / ageing environment. • The rolling thin film oven provides a good indication of ageing under typical conditions of manufacturing and laying. [ABSTRACT FROM AUTHOR]

In this paper, the mechanism of chloride ion transport in unsaturated concrete considering the nonlinear seepage effect is investigated by indoor experiments and analytical modelling. The concrete sheet imbibition test is used to reveal the nonlinear characters of seepage including water convection and moisture capillary within the unsaturated concrete in case of various water-binder ratios. For modelling purpose, an exponential function is introduced to mathematically depict the nonlinear relation between the specific discharge and hydraulic gradient during both water convection and moisture capillary processes. Based on such nonlinear seepage models, new mathematical models are proposed for the problem of chloride invasion within the reinforced concrete structure. The solution for the mathematical model of chloride transport is resolved by Laplace transform and finite difference method, of which acceptability is verified by the comparison with the results from chloride ion invasion test. The result indicates that, compared with linear seepage law, the use of the proposed nonlinear seepage solution is preferred to depict the saturation-relative humidity curves from concrete sheet imbibition test. The consideration of nonlinear seepage can result in a slower chloride transport rate, which further makes a later flow start-up time and a smaller free chloride iron concentration within the concrete. Such effect can be enhanced with the increase of nonlinear flow degree. The paper provides an effective solution to evaluate the chloride invasion within the unsaturated concrete. • Pioneer proposes solutions considering nonlinear seepage effect on chloride transport within concrete. • Considering nonlinear seepage can better describe the relationship between saturation and relative humidity. • The start-up time of nonlinear flow obviously lags behind that of linear flow. • The occurrence of nonlinear convection-diffusion and capillary diffusion seepage can slow down the penetration of chloride ions. [ABSTRACT FROM AUTHOR]

The paper evaluates the sensitivity of sonic tomography imaging of historic masonry structures to variations in stress level and damage. Six stone masonry walls with different geometries representative of historical typologies were constructed by a professional mason. A laboratory campaign was carried out, subjecting the walls to cyclic uniaxial compression tests. During the test, an automated sonic tomography system was used to inspect the wall under loading cycles of increasing amplitude, which led to obtain tomographic images during loading and compare them under different stress level and damage condition. The use of robotic systems was proved essential to carry out the sonic inspections simultaneously to the compression tests. Results show that sonic wave propagation is not only sensitive to damage level, but also to the stress state. Thus, sonic tomography has the potential to be used to measure damage and stress level of masonry components over time, for example during renovation works on an existing construction. • A novel automated sonic tomography system has been used to inspect masonry walls during laboratory tests. • Sonic tomography of stone masonry structures is sensitive to variations in the stress level and damage propagation. • Automated sonic tomographic systems may be used to monitor historic buildings during construction works. • The paper explores the correlation between the sonic wave velocity through stone masonry and material properties. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of CO 2 concentration and water on bonding strength evolution of the steel-concrete interface, this paper studied the carbonation process at the steel-concrete interface of composite samples in dry gas, pure water and 70% relative humidity (RH) environments with 100 kPa, 500 kPa and 1000 kPa CO 2 partial pressures. The results showed that the formation of aragonite and Fe(OH) 3 at the interface had a negative effect on the bonding strength, while the formation of calcite at the interface had a positive effect on the bonding strength. Also, the reaction environment had a noticeable effect on Fe-bearing corrosion products formed at the interface. In summary, if the concentration and the pressure of CO 2 reach a certain level (i.e., 100% concentration and 1000 kPa partial pressure or higher) and abundant water is present, the CO 2 -induced carbonation of concrete and corrosion of steel can eventually lead to damage at the steel-concrete interface. • This paper studied the mechanical degradation of the steel-concrete interface caused by high concentration CO 2. • A pure water environment induced formation of aragonite and Fe(OH) 3 , which caused a decrease in the bonding strength at the interface. • A dry gas environment induced formation of calcite, which caused an increase in the bonding strength at the interface. [ABSTRACT FROM AUTHOR]

To address the challenge posed by traditional methods of modifying recycled concrete aggregates (RCA), which struggle to achieve properties comparable to natural coarse aggregates (NCA) while ensuring a high utilization rate, this paper proposes a combination of freeze-thaw modification and sodium silicate modification. The process subjects the RCA to freeze-thaw cycles (FTC) to detach the attached mortar, which results in the extraction of recycled aggregates (Near-NCA) with properties similar to NCA, along with the spalling mortar (SM). These materials are used in the recycled concrete and mortar, respectively. Considering the inferior properties of SM, sodium silicate solutions are employed to modify it, serving as a replacement for river sand in the recycled mortar. The outcomes reveal that concrete cast using Near-NCA demonstrates mechanical properties comparable to ordinary concrete. Furthermore, the sodium silicate proves to be effective in modifying SM, reducing its crushed index and water absorption by approximately 30%. Through the SEM and XRD, it is determined that these improvements can be attributed to the formation of C-S-H gel. Finally, a multi-objective model is developed to consider modification effects, carbon emissions, energy consumption, economic and time costs, with the utilization of TOPSIS for determining the optimal modification plan. • This paper proposes a method that combines freeze-thaw modification with mineralization strengthening. • Modifying spalling mortar with sodium silicate solution can improve its various properties. • The modification mechanism of sodium silicate is investigated through microscopic tests. • The TOPSIS method is utilized to obtain the optimal modification scheme considering multiple objectives. [ABSTRACT FROM AUTHOR]

Using geopolymer concrete (GC) is a technically feasible decarbonization strategy in the cement and concrete industry shown by numerous papers. A key factor determining its commercial application is whether its cost is competitive. However, related study is scarce. In this paper, we present the analysis of GC's CO 2 avoidance cost, the cost incurred to reduce one metric ton of CO 2 emissions. The results show that among the 486 GC mixtures analyzed, only seven yield negative CO 2 avoidance costs, while 379 are even more expensive than capturing CO 2 from cement plants, which is another technically feasible decarbonization strategy and has been evaluated to have a CO 2 avoidance cost of 55 USD/tCO 2 in Chinese demonstration project. Only a few GC mixtures with lower CO 2 avoidance costs will be considered by the industry, and they are associated with low activator dosage and high compressive strength. To quantify this relationship, we introduce the activator index (Ai), which refers to the activator dosage (kg·m−3) required to achieve 1 MPa of compressive strength. The result shows that Ai values below certain thresholds correspond to lower CO 2 avoidance costs and significant emission reductions of GC. This Ai -based criterion helps identify the optimal GC mixture that effectively reduces CO 2 emissions at the lowest possible cost, thereby promoting its commercial application. [Display omitted] • Only 7 of 486 geopolymer concrete (GC) mixtures have negative CO 2 avoidance costs. • CO 2 avoidance costs of most GC in literature exceed CO 2 capture. • The lower activator dosage per MPa strength, the lower CO 2 avoidance cost of GC. [ABSTRACT FROM AUTHOR]