Pub Date : 2026-07-01Epub Date: 2025-12-13DOI: 10.1016/j.cscm.2025.e05696
Jianchao Zhang , Hongxi Liu , Zejian Lin , Zhuang Li , Peng Dong , Yu Zheng
This study proposed a multi–objective optimization framework for designing self-compacting concrete (SCC) with tunable mechanical property, workability, and durability. Leveraging the non–dominated sorting genetic algorithm II (NSGA–II), three critical mixture parameters: fly ash incorporation (0–50 %, in relation to the cement content), sand content (7.6–8.8 kg), and water reducing agent (0.021–0.033 kg) were optimized to balance conflicting performance objectives. Experimental validation and microstructure analysis confirmed that a 34 % fly ash incorporation, 8.47 kg sand, and 0.0286 kg water reducing agent achieved optimal strength (74.83 MPa at 28 days), slump flow (730.88 mm), and low water absorption (1.36 %). The established optimization method effectively resolved tradeoffs, enabling tailored SCC designs for mechanical property–required, workability–critical, or durability–focused applications. The derived Pareto–optimal solutions provided context–dependent mixtures, demonstrating better performance improvements over conventional designs.
{"title":"Engineering high–performance SCC through multidimensional tradeoffs: Co–optimizing mechanical property, workability, and durability","authors":"Jianchao Zhang , Hongxi Liu , Zejian Lin , Zhuang Li , Peng Dong , Yu Zheng","doi":"10.1016/j.cscm.2025.e05696","DOIUrl":"10.1016/j.cscm.2025.e05696","url":null,"abstract":"<div><div>This study proposed a multi–objective optimization framework for designing self-compacting concrete (SCC) with tunable mechanical property, workability, and durability. Leveraging the non–dominated sorting genetic algorithm II (NSGA–II), three critical mixture parameters: fly ash incorporation (0–50 %, in relation to the cement content), sand content (7.6–8.8 kg), and water reducing agent (0.021–0.033 kg) were optimized to balance conflicting performance objectives. Experimental validation and microstructure analysis confirmed that a 34 % fly ash incorporation, 8.47 kg sand, and 0.0286 kg water reducing agent achieved optimal strength (74.83 MPa at 28 days), slump flow (730.88 mm), and low water absorption (1.36 %). The established optimization method effectively resolved tradeoffs, enabling tailored SCC designs for mechanical property–required, workability–critical, or durability–focused applications. The derived Pareto–optimal solutions provided context–dependent mixtures, demonstrating better performance improvements over conventional designs.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05696"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145788588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-07-01Epub Date: 2025-12-19DOI: 10.1016/j.cscm.2025.e05717
Dong Tang , Hailin Wang , Naitian Zhang , Jin Ran , Yongli Zhao , Jing Li
Reflection cracking is a critical issue affecting the durability of semi-rigid base asphalt pavements, primarily caused by the high shrinkage and limited crack resistance of conventional cement-stabilized macadam (CSM). To address this, a filling-type large-size cement-stabilized macadam (F-LSBC) base was developed, yet its interfacial weakening mechanism and corresponding impact on energy evolution remain unclear. This study combines micro- and macro-scale investigations to elucidate the crack resistance mechanism of F-LSBC compared with CSM. Nanoindentation testing was employed to quantify the micromechanical properties of the interfacial transition zone (ITZ), while splitting load–unload tests were conducted to analyze the releasable elastic strain energy and surface-layer energy evolution of the two materials. Results show that the ITZ in F-LSBC exhibits significantly lower elastic modulus (60 %–75 %) and hardness (55 %) than in CSM, along with higher porosity and a 1.5-fold larger volume fraction, confirming a pronounced interfacial weakening structure. Correspondingly, the dissipated energy proportion in F-LSBC reaches about 75 %, notably higher than the 60 % observed in CSM, leading to a 50 % reduction in its energy storage limit and a surface-layer energy less than 40 % that of CSM. These findings indicate that the intentional interfacial weakening in F-LSBC effectively reduces the transmission of shrinkage strain energy to the surface layer, thereby suppressing the formation of reflection cracks. This study provides the first quantitative nanoindentation-based confirmation of ITZ weakening in F-LSBC and provides quantitative evidence supporting the linkage between ITZ weakening and the reduction of surface-layer energy peak, offering theoretical guidance for the design of anti-cracking semi-rigid base materials.
{"title":"Interfacial weakening mechanism and energy evolution of filling-type large-size cement-stabilized macadam for reflection crack mitigation","authors":"Dong Tang , Hailin Wang , Naitian Zhang , Jin Ran , Yongli Zhao , Jing Li","doi":"10.1016/j.cscm.2025.e05717","DOIUrl":"10.1016/j.cscm.2025.e05717","url":null,"abstract":"<div><div>Reflection cracking is a critical issue affecting the durability of semi-rigid base asphalt pavements, primarily caused by the high shrinkage and limited crack resistance of conventional cement-stabilized macadam (CSM). To address this, a filling-type large-size cement-stabilized macadam (F-LSBC) base was developed, yet its interfacial weakening mechanism and corresponding impact on energy evolution remain unclear. This study combines micro- and macro-scale investigations to elucidate the crack resistance mechanism of F-LSBC compared with CSM. Nanoindentation testing was employed to quantify the micromechanical properties of the interfacial transition zone (ITZ), while splitting load–unload tests were conducted to analyze the releasable elastic strain energy and surface-layer energy evolution of the two materials. Results show that the ITZ in F-LSBC exhibits significantly lower elastic modulus (60 %–75 %) and hardness (55 %) than in CSM, along with higher porosity and a 1.5-fold larger volume fraction, confirming a pronounced interfacial weakening structure. Correspondingly, the dissipated energy proportion in F-LSBC reaches about 75 %, notably higher than the 60 % observed in CSM, leading to a 50 % reduction in its energy storage limit and a surface-layer energy less than 40 % that of CSM. These findings indicate that the intentional interfacial weakening in F-LSBC effectively reduces the transmission of shrinkage strain energy to the surface layer, thereby suppressing the formation of reflection cracks. This study provides the first quantitative nanoindentation-based confirmation of ITZ weakening in F-LSBC and provides quantitative evidence supporting the linkage between ITZ weakening and the reduction of surface-layer energy peak, offering theoretical guidance for the design of anti-cracking semi-rigid base materials.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05717"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-07-01Epub Date: 2025-12-16DOI: 10.1016/j.cscm.2025.e05710
Shuqiong Luo , Shilei Gui , Lei Yang , Zhuangzhuang Jiang , Minghui Zhao , Guowen Sun , Zhenhe Tian , Jun Ren
Microwave hydrothermal synthesis can provide a sustainable way to prepare tobermorite, which can potentially efficiently solidify heavy metals by replacing calcium or silicon within its structure of tobermorite. In this paper, the feasibility of microwave hydrothermal process in solidifying heavy metal zinc (Zn) was investigated. The tobermorite was prepared from fumed silica and calcium hydroxide at Ca/Si of 0.83. The Zn-substituted tobermorite (Zn-tobermorite) was then prepared by adding Zinc chlorine under the Zn/Ca ratios of 0.05, 0.1, 0.15, 0.2, respectively. Additionally the characterisation of hydration product and the leaching behaviour of immobilised Zn was detected. Results indicated that the primary reaction products under both microwave and conventional hydrothermal conditions were Zn-tobermorite, tobermorite, gyrolite, hemimorphite, and reinhardbraunsite. During the synthesis of Zn-tobermorite, Zn²⁺ ions substituted for Ca²⁺ at an optimal Zn/Ca ratio of 0.15, achieving a Zn immobilization efficiency of 99.9 %. The microwave-assisted hydrothermal process reduced the synthesis time by approximately 85 % from 14 h to 2 h compared to conventional methods, while maintaining similar immobilization performance. This work offers a sustainable and time-efficient approach for heavy metal immobilization, showing significant potential for large-scale environmental remediation in industrial settings.
{"title":"Sustainable microwave-hydrothermal synthesis for in-situ solidification of heavy-metal zinc in tobermorite","authors":"Shuqiong Luo , Shilei Gui , Lei Yang , Zhuangzhuang Jiang , Minghui Zhao , Guowen Sun , Zhenhe Tian , Jun Ren","doi":"10.1016/j.cscm.2025.e05710","DOIUrl":"10.1016/j.cscm.2025.e05710","url":null,"abstract":"<div><div>Microwave hydrothermal synthesis can provide a sustainable way to prepare tobermorite, which can potentially efficiently solidify heavy metals by replacing calcium or silicon within its structure of tobermorite. In this paper, the feasibility of microwave hydrothermal process in solidifying heavy metal zinc (Zn) was investigated. The tobermorite was prepared from fumed silica and calcium hydroxide at Ca/Si of 0.83. The Zn-substituted tobermorite (Zn-tobermorite) was then prepared by adding Zinc chlorine under the Zn/Ca ratios of 0.05, 0.1, 0.15, 0.2, respectively. Additionally the characterisation of hydration product and the leaching behaviour of immobilised Zn was detected. Results indicated that the primary reaction products under both microwave and conventional hydrothermal conditions were Zn-tobermorite, tobermorite, gyrolite, hemimorphite, and reinhardbraunsite. During the synthesis of Zn-tobermorite, Zn²⁺ ions substituted for Ca²⁺ at an optimal Zn/Ca ratio of 0.15, achieving a Zn immobilization efficiency of 99.9 %. The microwave-assisted hydrothermal process reduced the synthesis time by approximately 85 % from 14 h to 2 h compared to conventional methods, while maintaining similar immobilization performance. This work offers a sustainable and time-efficient approach for heavy metal immobilization, showing significant potential for large-scale environmental remediation in industrial settings.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05710"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-07-01Epub Date: 2025-12-22DOI: 10.1016/j.cscm.2025.e05725
Tianyu Cai , Zhi-Qi He , Wenjie Li
Placing a thin layer of ultra-high performance concrete (UHPC) locally in critical regions, particularly in negative-moment zones, provides an effective means to improve the flexural behavior and durability of concrete bridge girders while limiting UHPC usage. However, targeted experimental evidence on locally embedded UHPC-NC beams and systematic investigations of their flexural and interfacial responses remain limited. In this study, NC-UHPC composite beams with embedded thin UHPC layers (NC-UHPC-ETUL) with different section heights and reinforcement layouts were fabricated and tested under three-point bending to evaluate flexural behavior and interfacial performance. The results show that embedding a thin UHPC layer in the NC matrix increases flexural stiffness, delays crack initiation and propagation, and enhances ultimate load capacity. Specimens with through-reinforcement across the UHPC-NC interface exhibited more uniform crack patterns and greater ductility than those without. An analytical model was developed to predict stress distributions, interface-debonding loads, and flexural capacities, explicitly accounting for the mechanical interaction between the UHPC and NC layers; its predictions agreed well with the experimental results. The validated framework provides an effective and efficient tool for the preliminary design and assessment of NC-UHPC-ETUL beams.
{"title":"Experimental and theoretical study on the flexural behavior of NC-UHPC composite beams with embedded thin UHPC layers","authors":"Tianyu Cai , Zhi-Qi He , Wenjie Li","doi":"10.1016/j.cscm.2025.e05725","DOIUrl":"10.1016/j.cscm.2025.e05725","url":null,"abstract":"<div><div>Placing a thin layer of ultra-high performance concrete (UHPC) locally in critical regions, particularly in negative-moment zones, provides an effective means to improve the flexural behavior and durability of concrete bridge girders while limiting UHPC usage. However, targeted experimental evidence on locally embedded UHPC-NC beams and systematic investigations of their flexural and interfacial responses remain limited. In this study, NC-UHPC composite beams with embedded thin UHPC layers (NC-UHPC-ETUL) with different section heights and reinforcement layouts were fabricated and tested under three-point bending to evaluate flexural behavior and interfacial performance. The results show that embedding a thin UHPC layer in the NC matrix increases flexural stiffness, delays crack initiation and propagation, and enhances ultimate load capacity. Specimens with through-reinforcement across the UHPC-NC interface exhibited more uniform crack patterns and greater ductility than those without. An analytical model was developed to predict stress distributions, interface-debonding loads, and flexural capacities, explicitly accounting for the mechanical interaction between the UHPC and NC layers; its predictions agreed well with the experimental results. The validated framework provides an effective and efficient tool for the preliminary design and assessment of NC-UHPC-ETUL beams.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05725"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-07-01Epub Date: 2026-01-05DOI: 10.1016/j.cscm.2026.e05759
Yan-qing Fu , Bin Zeng , Hai-lin Chang , Chuang Cui
Prestressed bridge piers are widely used in cross-sea, urban municipal, and mountainous bridge construction. Conventional precast bridges usually use prestressed steel strands for anchoring, resulting in the corrosion and fracture of steel strands. A new high-strength cold-rolled prestressed coarse steel bars as a novel anchoring system is adopted as the research object. Considering the deterioration effect at the root of the thread, the influence of the number of cold rolling and tempering temperatures on the initial cracks and fatigue performance of steel bar is analyzed. Further, the small and full-scale fatigue tests on the steel bars are also carried out. The fatigue lifetimes of the two are compared, and a fatigue life assessment model based on the specimens of cold-rolled coarse steel bars is established. The average error of this prediction model is about 5 %, indicating a favorable predictive performance.
{"title":"Fatigue performance of ultra-high-strength cold-rolled prestressed large-diameter steel bars in prefabricated pier","authors":"Yan-qing Fu , Bin Zeng , Hai-lin Chang , Chuang Cui","doi":"10.1016/j.cscm.2026.e05759","DOIUrl":"10.1016/j.cscm.2026.e05759","url":null,"abstract":"<div><div>Prestressed bridge piers are widely used in cross-sea, urban municipal, and mountainous bridge construction. Conventional precast bridges usually use prestressed steel strands for anchoring, resulting in the corrosion and fracture of steel strands. A new high-strength cold-rolled prestressed coarse steel bars as a novel anchoring system is adopted as the research object. Considering the deterioration effect at the root of the thread, the influence of the number of cold rolling and tempering temperatures on the initial cracks and fatigue performance of steel bar is analyzed. Further, the small and full-scale fatigue tests on the steel bars are also carried out. The fatigue lifetimes of the two are compared, and a fatigue life assessment model based on the specimens of cold-rolled coarse steel bars is established. The average error of this prediction model is about 5 %, indicating a favorable predictive performance.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05759"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-07-01Epub Date: 2025-12-27DOI: 10.1016/j.cscm.2025.e05738
Lanjing Xing , Richeng Liu , Xiao Zhang , Minghui Hu , Yiyang Wang , Shuchen Li , Shaoshuai Pan , Xuntu Yin
Underground construction is advancing into greater depths and more complex geology, and tunnels in fractured rock frequently exhibit insufficient bearing capacity and uncontrolled deformation. Grouting reinforcement and lining support are widely adopted to improve the surrounding rock quality and provide passive support. To explore the synergistic mechanism between grouting and lining, this study conducted uniaxial compression tests on rock specimens containing a horseshoe-shaped opening with prefabricated cracks. The tests evaluated various combinations of grouting materials, namely polyurethane/water glass (PU/WG), ordinary Portland cement (OPC), and calcium sulfoaluminate (CSA), with lining materials including PU/WG, gypsum (GY), and CSA. The results show that grouting materials with high elastic modulus significantly improve the overall stiffness of the support system, increasing the bearing capacity by up to 66.8 %. The contribution of grouting to strength enhancement substantially exceeds that of the lining alone. Ductile linings such as PU/WG effectively restrain the relative horizontal widening ΔW/W0, reducing the ΔW/W0 to as low as 0.49 %. The rigid lining, such as CSA, is more conducive to controlling the relative vertical convergence ΔH/H0, lowering ΔH/H0 to 0.86 %. GY lining, due to its low tensile strength, tends to develop tensile cracks at the crown, resulting in significantly larger ΔH/H0. The optimal performance was achieved with a rigid-flexible combination of CSA grouting and PU/WG lining, which was limited to ΔH/H0= 1.1 % and ΔW/W0= 0.18 %. The failure pattern is transformed from the penetrating failure along the prefabricated crack to the crack initiation at the haunch and springing. These results highlight the importance of grouting materials with high elastic modulus for reinforcing defect zones, providing an experimental basis for synergistic grouting-lining design in fractured rock tunnels.
{"title":"Experimental study on grouting-lining synergistic support mechanism of horseshoe-shaped tunnel specimens with prefabricated cracks","authors":"Lanjing Xing , Richeng Liu , Xiao Zhang , Minghui Hu , Yiyang Wang , Shuchen Li , Shaoshuai Pan , Xuntu Yin","doi":"10.1016/j.cscm.2025.e05738","DOIUrl":"10.1016/j.cscm.2025.e05738","url":null,"abstract":"<div><div>Underground construction is advancing into greater depths and more complex geology, and tunnels in fractured rock frequently exhibit insufficient bearing capacity and uncontrolled deformation. Grouting reinforcement and lining support are widely adopted to improve the surrounding rock quality and provide passive support. To explore the synergistic mechanism between grouting and lining, this study conducted uniaxial compression tests on rock specimens containing a horseshoe-shaped opening with prefabricated cracks. The tests evaluated various combinations of grouting materials, namely polyurethane/water glass (PU/WG), ordinary Portland cement (OPC), and calcium sulfoaluminate (CSA), with lining materials including PU/WG, gypsum (GY), and CSA. The results show that grouting materials with high elastic modulus significantly improve the overall stiffness of the support system, increasing the bearing capacity by up to 66.8 %. The contribution of grouting to strength enhancement substantially exceeds that of the lining alone. Ductile linings such as PU/WG effectively restrain the relative horizontal widening Δ<em>W</em>/<em>W</em><sub>0</sub>, reducing the Δ<em>W</em>/<em>W</em><sub>0</sub> to as low as 0.49 %. The rigid lining, such as CSA, is more conducive to controlling the relative vertical convergence Δ<em>H</em>/<em>H</em><sub>0</sub>, lowering Δ<em>H</em>/<em>H</em><sub>0</sub> to 0.86 %. GY lining, due to its low tensile strength, tends to develop tensile cracks at the crown, resulting in significantly larger Δ<em>H</em>/<em>H</em><sub>0</sub>. The optimal performance was achieved with a rigid-flexible combination of CSA grouting and PU/WG lining, which was limited to Δ<em>H</em>/<em>H</em><sub>0</sub>= 1.1 % and Δ<em>W</em>/<em>W</em><sub>0</sub>= 0.18 %. The failure pattern is transformed from the penetrating failure along the prefabricated crack to the crack initiation at the haunch and springing. These results highlight the importance of grouting materials with high elastic modulus for reinforcing defect zones, providing an experimental basis for synergistic grouting-lining design in fractured rock tunnels.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05738"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-07-01Epub Date: 2026-01-08DOI: 10.1016/j.cscm.2026.e05772
Wang Pan , Hongxin Guan , Jie Deng , Hairong Yang
Traditional polyurethane-modified road asphalt (PU-RA) relies on fossil resources and has high costs, and bio-based materials provide a new path for its green development. This study prepared lignin-polyurethane modified road asphalt (LPU-RA) using sodium lignosulfonate (LS) as a bio-based alternative component, aimed at clarifying how LS regulates LPU-RA performance and its core mechanism. FTIR, FM and AFM were used to characterize chemical structure and micromorphology, combined with molecular dynamics (MD) simulation to analyze intermolecular interactions. The results show that LPU-RA achieves optimal comprehensive performance when LS replaces 10 % polyols, with its core properties including high/low-temperature resistance and rutting resistance significantly improved compared with PU-RA. LS’s rigid benzene rings covalently bond with polyurethane (PU) flexible chains via urethane bonds, forming a "rigid-flexible" interpenetrating network to inhibit microphase separation. MD simulation confirms that PU/LS group enrichment improves surface free energy, and hydrogen bonds between LS and asphaltenes strengthen molecular binding, jointly optimizing performance. The clarified "bio-based component-microstructure-macro-performance" mechanism and optimal LS ratio provide theoretical support for directional design of bio-based modified asphalt.
{"title":"\"Rigid-Flexible\" interpenetrating network: Performance regulation & multi-scale mechanism of lignin – Polyurethane composite asphalt","authors":"Wang Pan , Hongxin Guan , Jie Deng , Hairong Yang","doi":"10.1016/j.cscm.2026.e05772","DOIUrl":"10.1016/j.cscm.2026.e05772","url":null,"abstract":"<div><div>Traditional polyurethane-modified road asphalt (PU-RA) relies on fossil resources and has high costs, and bio-based materials provide a new path for its green development. This study prepared lignin-polyurethane modified road asphalt (LPU-RA) using sodium lignosulfonate (LS) as a bio-based alternative component, aimed at clarifying how LS regulates LPU-RA performance and its core mechanism. FTIR, FM and AFM were used to characterize chemical structure and micromorphology, combined with molecular dynamics (MD) simulation to analyze intermolecular interactions. The results show that LPU-RA achieves optimal comprehensive performance when LS replaces 10 % polyols, with its core properties including high/low-temperature resistance and rutting resistance significantly improved compared with PU-RA. LS’s rigid benzene rings covalently bond with polyurethane (PU) flexible chains via urethane bonds, forming a \"rigid-flexible\" interpenetrating network to inhibit microphase separation. MD simulation confirms that PU/LS group enrichment improves surface free energy, and hydrogen bonds between LS and asphaltenes strengthen molecular binding, jointly optimizing performance. The clarified \"bio-based component-microstructure-macro-performance\" mechanism and optimal LS ratio provide theoretical support for directional design of bio-based modified asphalt.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05772"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-07-01Epub Date: 2026-01-05DOI: 10.1016/j.cscm.2026.e05761
Khalid Saqer Alotaibi, Abdulsalam Mohammed Alkhalaf
This study presents a robust and interpretable machine learning framework for predicting the average bond strength () of cement-based adhesives in Near-Surface Mounted (NSM) FRP systems. Four state-of-the-art ensemble algorithms were evaluated on a dataset of 150 experimental tests using a rigorous nested cross-validation protocol and Differential Evolution for hyperparameter optimization. A key aspect of the framework is the explicit engineering of interaction terms to model physical synergies. The optimized LightGBM model emerged as the superior predictor, achieving a mean R² of 0.42 on unseen test data while fitting the training data with an R² of 0.79. This contrast reflects the high heterogeneity of the aggregated dataset. A SHAP analysis revealed that engineered interaction terms were the most influential predictors across all models, with the interplay between groove depth and surface treatment ( · Treatment) consistently highly ranked. For the best-performing LightGBM model specifically, the synergy between surface treatment and FRP tensile strength () proved most dominant. These findings highlight that the predictive power of primary variables is significantly enhanced when their complex interdependencies are explicitly modeled. This work provides a transparent, methodologically rigorous framework that serves as both a predictive tool and an instrument for scientific insight into NSM FRP bond mechanics.
{"title":"Interpretable machine learning framework for predicting cement adhesive bond strength in NSM FRP systems using differential evolution and SHAP analysis","authors":"Khalid Saqer Alotaibi, Abdulsalam Mohammed Alkhalaf","doi":"10.1016/j.cscm.2026.e05761","DOIUrl":"10.1016/j.cscm.2026.e05761","url":null,"abstract":"<div><div>This study presents a robust and interpretable machine learning framework for predicting the average bond strength (<span><math><msub><mrow><mi>τ</mi></mrow><mrow><mi>avg</mi></mrow></msub></math></span>) of cement-based adhesives in Near-Surface Mounted (NSM) FRP systems. Four state-of-the-art ensemble algorithms were evaluated on a dataset of 150 experimental tests using a rigorous nested cross-validation protocol and Differential Evolution for hyperparameter optimization. A key aspect of the framework is the explicit engineering of interaction terms to model physical synergies. The optimized LightGBM model emerged as the superior predictor, achieving a mean R² of 0.42 on unseen test data while fitting the training data with an R² of 0.79. This contrast reflects the high heterogeneity of the aggregated dataset. A SHAP analysis revealed that engineered interaction terms were the most influential predictors across all models, with the interplay between groove depth and surface treatment (<span><math><msub><mrow><mi>d</mi></mrow><mrow><mi>g</mi></mrow></msub></math></span> · Treatment) consistently highly ranked. For the best-performing LightGBM model specifically, the synergy between surface treatment and FRP tensile strength (<span><math><msub><mrow><mi>f</mi></mrow><mrow><mi>frp</mi></mrow></msub></math></span>) proved most dominant. These findings highlight that the predictive power of primary variables is significantly enhanced when their complex interdependencies are explicitly modeled. This work provides a transparent, methodologically rigorous framework that serves as both a predictive tool and an instrument for scientific insight into NSM FRP bond mechanics.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05761"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-07-01Epub Date: 2026-01-05DOI: 10.1016/j.cscm.2026.e05756
Lifeng Liu , Qinghua Zhang , Jianhong Ding , Shucheng Tan , Feipeng Liu , Ting Sun
Ecological concrete is a sustainable material that supports vegetation growth and promotes ecosystem restoration. However, its development is constrained by material limitations and insufficient understanding of vegetation-concrete interactions. Although the preparation process and water purification performance of ecological concrete made with volcanic rock aggregate have been preliminarily reported, key properties such as microstructure, porosity, pH, and long-term vegetation adaptability remain insufficiently investigated. In this study, ecological concrete using volcanic rock aggregate was prepared. The mix design and preparation process were optimized, and compressive strength, porosity, pH, microstructure, alkalinity reduction, and vegetation performance were systematically evaluated. The results showed that ecological concrete made with volcanic rock aggregate exhibited favorable physical-mechanical properties, with a 28-day compressive strength of 5.5–9.1 MPa, an effective porosity of 23.0–27.4 %, and a reducible pH of 8.3. Optimal performance (24.4 % porosity and 9.1 MPa strength) was achieved at an aggregate-to-cement ratio of 3.5. The compressive strength and porosity were jointly affected by the mix proportion, preparation method, and internal pore structure of the volcanic rock aggregate. The combination of low-alkalinity sulfoaluminate cement and a 2 % oxalic acid solution effectively reduced alkalinity; however, the oxalic acid concentration, spraying volume, and treatment frequency must be carefully controlled to minimize adverse effects on microscopic morphology. In addition, the concrete demonstrated satisfactory vegetation performance. After nine months, the average grass height reached 52.0 cm. Roots extensively penetrated specimens with thicknesses of 6 cm, 8 cm, and 10 cm, with penetration resistance gradually increasing; penetration was markedly inhibited in 15 cm thick specimens. Therefore, a concrete thickness of 6–10 cm is recommended.
{"title":"Experimental study on the physical-mechanical properties and vegetation performance of ecological concrete made with volcanic rock aggregates","authors":"Lifeng Liu , Qinghua Zhang , Jianhong Ding , Shucheng Tan , Feipeng Liu , Ting Sun","doi":"10.1016/j.cscm.2026.e05756","DOIUrl":"10.1016/j.cscm.2026.e05756","url":null,"abstract":"<div><div>Ecological concrete is a sustainable material that supports vegetation growth and promotes ecosystem restoration. However, its development is constrained by material limitations and insufficient understanding of vegetation-concrete interactions. Although the preparation process and water purification performance of ecological concrete made with volcanic rock aggregate have been preliminarily reported, key properties such as microstructure, porosity, pH, and long-term vegetation adaptability remain insufficiently investigated. In this study, ecological concrete using volcanic rock aggregate was prepared. The mix design and preparation process were optimized, and compressive strength, porosity, pH, microstructure, alkalinity reduction, and vegetation performance were systematically evaluated. The results showed that ecological concrete made with volcanic rock aggregate exhibited favorable physical-mechanical properties, with a 28-day compressive strength of 5.5–9.1 MPa, an effective porosity of 23.0–27.4 %, and a reducible pH of 8.3. Optimal performance (24.4 % porosity and 9.1 MPa strength) was achieved at an aggregate-to-cement ratio of 3.5. The compressive strength and porosity were jointly affected by the mix proportion, preparation method, and internal pore structure of the volcanic rock aggregate. The combination of low-alkalinity sulfoaluminate cement and a 2 % oxalic acid solution effectively reduced alkalinity; however, the oxalic acid concentration, spraying volume, and treatment frequency must be carefully controlled to minimize adverse effects on microscopic morphology. In addition, the concrete demonstrated satisfactory vegetation performance. After nine months, the average grass height reached 52.0 cm. Roots extensively penetrated specimens with thicknesses of 6 cm, 8 cm, and 10 cm, with penetration resistance gradually increasing; penetration was markedly inhibited in 15 cm thick specimens. Therefore, a concrete thickness of 6–10 cm is recommended.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05756"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-07-01Epub Date: 2026-01-05DOI: 10.1016/j.cscm.2026.e05760
Yaocheng Wang , Xu Li , Yu Jin , Chaoqun Zeng
To address the significant CO2 emissions of commercial water glass, the utilization of alkali activators prepared from waste glass is a viable solution. However, it is important to note that these activators frequently contain aluminum (Al) impurities, which have been reported to affect the initial dissolution behavior of slag. But the impact of Al impurities on the compressive strength and hydration of alkali-activated slag remains inadequately understood. Consequently, the compressive strength, hydration, hydration products, calcium aluminosilicate hydrate gel properties, and pore structure of slag activated by water glass containing different concentrations of Al impurities were investigated. The findings reveal that Al impurities in water glass cause a reduction and delay in the second exothermic peak, regardless of slag composition. Despite this, their long-term influence on pore structure, compressive strength, and phase assemblage is minimal and can be considered negligible across different types of slag.
{"title":"Effect of aluminum impurities within water glass on the compressive strength and hydration of alkali-activated slag","authors":"Yaocheng Wang , Xu Li , Yu Jin , Chaoqun Zeng","doi":"10.1016/j.cscm.2026.e05760","DOIUrl":"10.1016/j.cscm.2026.e05760","url":null,"abstract":"<div><div>To address the significant CO<sub>2</sub> emissions of commercial water glass, the utilization of alkali activators prepared from waste glass is a viable solution. However, it is important to note that these activators frequently contain aluminum (Al) impurities, which have been reported to affect the initial dissolution behavior of slag. But the impact of Al impurities on the compressive strength and hydration of alkali-activated slag remains inadequately understood. Consequently, the compressive strength, hydration, hydration products, calcium aluminosilicate hydrate gel properties, and pore structure of slag activated by water glass containing different concentrations of Al impurities were investigated. The findings reveal that Al impurities in water glass cause a reduction and delay in the second exothermic peak, regardless of slag composition. Despite this, their long-term influence on pore structure, compressive strength, and phase assemblage is minimal and can be considered negligible across different types of slag.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05760"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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