Case Studies in Construction Materials最新文献

{"title":"Creep failure of alkali activated slag concrete in compression: Effect of loading age and stress level","authors":"Ziyang Zhang ,&nbsp;Xianggang Bian ,&nbsp;Jianfei Kang ,&nbsp;Tengfei Xu","doi":"10.1016/j.cscm.2025.e05744","DOIUrl":"10.1016/j.cscm.2025.e05744","url":null,"abstract":"<div><div>With the rapid advancement of 3D printing, concrete is required to bear significant stress loads during its early-age period. The high stress creep failure behavior is directly associated with the structural stability and build ability requirements of 3D printed concrete elements during layer deposition. Nonlinear creep manifests in concrete subjected to high stresses. This process results in the accumulation of damage, which culminates in creep failure of concrete materials. However, limited information exists on this phenomenon in alkali-activated slag concrete. In this study, the creep failure of alkali-activated slag concrete under high uniaxial stress was investigated, and the creep failure characteristics of alkali-activated slag concrete were obtained. Additionally, the effects of loading age and stress ratio were investigated. The failure mechanism, creep coefficient, and nominal Poisson’s ratio of alkali-activated slag concrete specimens were investigated. Findings indicated that as age increases, the influence of loading age on the nonlinear creep of alkali-activated slag concrete progressively diminishes. Stress levels significantly affect the nonlinear creep of alkali-activated slag concrete. Specifically, when the stress level reached 0.95<span><math><msub><mrow><mi>f</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>, the alkali-activated slag concrete specimen failed after sustaining the load for a few seconds. During the creep phase, the circumferential creep coefficient and nominal Poisson’s ratio of the specimen exhibited a substantial increase, with the circumferential creep coefficient markedly exceeding the axial creep coefficient. Furthermore, the specimens exhibited significant lateral expansion upon destruction. Non-destructive and crack analyses were conducted to identify the creep-failure mechanism. The creep-failure study indicated that the propagation of microcracks inside the specimen influenced the nonlinear creep and creep-failure characteristics of alkali-activated slag concrete specimens subjected to high sustained compressive stress. The deterioration of the adhesive substance between particles progressively culminated in extensive fractures, which resulted in creep failure.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05744"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921559","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}

{"title":"Prediction of the hydration heat, temperature distribution and thermal stress of mass concrete","authors":"Guowen Sun ,&nbsp;Haorui Zheng ,&nbsp;Liguo Wang ,&nbsp;Liang Peng ,&nbsp;Haitao Yang ,&nbsp;Yifan Li","doi":"10.1016/j.cscm.2025.e05748","DOIUrl":"10.1016/j.cscm.2025.e05748","url":null,"abstract":"<div><div>Thermal cracks induced by hydration heat are one of the primary factors affecting the durability of mass concrete structures. To accurately predict the early-age temperature rise and thermal stress of mass concrete, a hydration heat prediction model for Portland cement was established based on the Parrot-Killoh hydration kinetic model, considering the effects of water-cement ratio, cement fineness, relative humidity and temperature. Subsequently, taking the predicted hydration heat as the internal heat source, a finite element analysis model for the temperature and thermal stress fields of mass concrete was constructed. The influence laws of key parameters including water-cement ratio, cement fineness and curing temperature on the core temperature and thermal stress were systematically investigated. The results indicate that reducing the water-cement ratio or using finer cement significantly increases the peak core temperature and peak compressive stress of concrete; an increase in curing temperature accelerates the hydration reaction, raises the peak temperature and reduces the late-age tensile stress. Furthermore, a thermo-mechanical-damage coupled model based on the Mazars damage criterion was employed to simulate the early-age damage evolution process, revealing that damage tends to occur on the surface and edge regions within 24 h after casting. The multi-scale prediction method proposed in this study provides a reliable theoretical tool and engineering reference for temperature control and crack prevention design of mass concrete.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05748"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921668","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}

{"title":"Experimental investigation of HPMC inhibited crack sensitive of coral mud under extreme environmental conditions","authors":"Hong Wang ,&nbsp;Chunyan Wang ,&nbsp;Jinqiao Zhao ,&nbsp;Zhenhua Ren ,&nbsp;Xuanming Ding","doi":"10.1016/j.cscm.2026.e05762","DOIUrl":"10.1016/j.cscm.2026.e05762","url":null,"abstract":"<div><div>Coral mud, widely distributed in the South China Sea, is highly prone to cracking, posing challenges for engineering applications. Hydroxypropyl methyl cellulose (HPMC), with superior water retention and crack inhibition capacity under hot and humid conditions, was introduced to improve the crack resistance of coral mud. This study conducted cracking and tensile tests to evaluate the effects of HPMC dosage (four levels) and environmental conditions on the cracking behavior and mechanical properties of coral mud. Results show that temperature and humidity markedly regulate water evaporation, with high temperature significantly accelerating moisture loss. HPMC effectively enhanced water retention and delayed cracking, with a 0.25 % dosage providing the optimal performance. It restricted crack length and refined crack width distribution while having little influence on crack orientation. The modification efficacy was strongly dependent on environmental conditions, showing the most significant improvement under high temperature and high humidity, where a 0.25 % dosage markedly enhanced crack resistance. Tensile tests confirmed that HPMC enhanced interparticle bonding and force transfer, particularly under high water content, whereas the effect was limited under low water content. This paper discussed the dual mechanism of HPMC to suppress cracking in coral mud by regulating evaporation and enhancing cohesion based on experimental results. Its findings provide practical guidelines for dosage and condition-specific application, supporting sustainable infrastructure development in the South China Sea.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05762"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921747","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}

{"title":"Experimental and theoretical investigation of fiber-reinforced geopolymer mortars: Mix design optimization and bond behavior with brick masonry","authors":"Lihua Niu ,&nbsp;Xueying Nie ,&nbsp;Nan Li ,&nbsp;Junfeng Guan ,&nbsp;Lielie Li ,&nbsp;Chaopeng Xie ,&nbsp;Shaohua Gao","doi":"10.1016/j.cscm.2026.e05767","DOIUrl":"10.1016/j.cscm.2026.e05767","url":null,"abstract":"<div><div>Despite being utilized for thousands of years, masonry structures still face significant challenges in enhancing their integrity and durability, making the preservation of architectural heritage and the development of innovative repair solutions critical. Geopolymer mortar (GM), an environmentally friendly alternative to traditional cement-based materials, shows considerable promise in both new construction and repair of masonry structures. This study systematically investigated the effects of water-binder ratio, binder-sand ratio, water-reducing agent content, and curing age on the setting time, fluidity, compressive strength, and flexural strength of GM. Additionally, the bond strength between GM with different mix ratios and brick masonry was thoroughly examined, along with the bonding performance of fiber-reinforced geopolymer mortar (FRGM) with brick masonry. The findings of this study demonstrated that the water-binder ratio was a crucial factor influencing the workability of GMs. An increase in this ratio significantly prolonged the setting time and improved flowability, while the binder-sand ratio played a secondary role in affecting workability. The mechanical strength of GMs significantly improved by reducing both the water-binder and binder-sand ratios, as well as with prolonged curing. The optimal dosage of a superplasticizer effectively enhanced mortar strength. In addition, the shear bond strength between GM and brick masonry progressively decreased with increasing water-binder and binder-sand ratios. A model for calculating bond strength was proposed, with theoretical values closely aligning with experimental results. The bond strength between FRGM and brick masonry significantly increased with extended bond length, though the rate of increase gradually declined. The bond strength between carbon fiber mesh-reinforced geopolymer mortar and brick masonry was the highest among the three types of fiber meshes. Basalt fiber mesh exhibited a comparable bond strength, and glass fiber mesh exhibited the lowest bond strength. This study provided important experimental and theoretical support for the design and optimization of high-performance GMs in engineering structure application.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05767"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921750","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}

{"title":"Enhancing early strength of cement mortar using MSWI fly ash under accelerated carbonation curing","authors":"Minseok Nam ,&nbsp;Yunsu Lee ,&nbsp;Jeado Han ,&nbsp;Dongkyu Lee ,&nbsp;Sungwon Jung ,&nbsp;Myung-Sun Baek ,&nbsp;Dongcheon Park ,&nbsp;Kwangwoo Wi","doi":"10.1016/j.cscm.2026.e05779","DOIUrl":"10.1016/j.cscm.2026.e05779","url":null,"abstract":"<div><div>Metallic Al in municipal solid waste incineration fly ash (MSWIFA) generates hydrogen gas in cement mortars, creating internal pores that typically reduce mechanical strength and necessitate pretreatment before use. This study aims to utilize these gas-induced pores as diffusion pathways for CO₂ during carbonation curing to maximize its effectiveness in cement mortars. Cement paste and mortar specimens were prepared by replacing cement with 2.5, 5, and 10 wt% of untreated MSWIFA. Their physical and chemical properties were evaluated through flowability, calorimetry, compressive strength, porosity, water absorption, Fourier-transform infrared spectroscopy, thermogravimetric-differential thermal analysis, and inductively coupled plasma tests. The chlorides in MSWIFA accelerated cement hydration but reduced flowability owing to increased viscosity. Although gas-induced pores reduced strength, they facilitated CO₂ penetration, which contributed to strength improvement through densification. Notably, the sample with 5 % MSWIFA (AFA5) showed the highest compressive strength after carbonation. In all specimens, Ca(OH)₂ and C-S-H transformed into CaCO₃, with AFA5 forming more metastable CaCO₃. Heavy metals such as Cu, Zn, and Pb were effectively immobilized by hydration products, while Cr leaching slightly increased owing to electrostatic repulsion. Carbonation resulted in a slight increase in heavy metal leaching; however, all values remained below the regulatory limits established by the United States Environmental Protection Agency, confirming the environmental safety.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05779"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921820","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}

{"title":"A deep learning framework for microstructural analysis of nano-modified cementitious composites using metal intrusion and BSE imaging","authors":"Zixuan Yu ,&nbsp;Shuai Liang ,&nbsp;Tong Liu ,&nbsp;Yifei Ma ,&nbsp;Yining Lin ,&nbsp;Yuan Gao ,&nbsp;Yanming Liu ,&nbsp;Jinpeng Wang","doi":"10.1016/j.cscm.2025.e05694","DOIUrl":"10.1016/j.cscm.2025.e05694","url":null,"abstract":"<div><div>Nanomodification is a promising technology for advancing construction materials toward multifunctionality, intelligence, and sustainability. However, current assessments of its effects on microstructure modification require improvements in objectivity, quantification, and pattern generalization. This study proposes a novel characterization-analysis framework, integrating metal intrusion technology with deep learning to enable expertise-independent extraction and evaluation of microstructure characteristics. Using image-based algorithms, the optimization of nanopore structure in cementitious waste rockfill material is first described. Based on a dataset comprising over 4000 microscopic images, the proposed deep learning model achieved a maximum 82.0 % accuracy at a 39.7 μm × 39.7 μm observation scale in distinguishing microstructure images of samples with various water-cement ratios and graphene oxide (GO) reinforcement. Porosity and fractal dimension show weak correlation with classification accuracy, suggesting insufficient description of these parameters on microstructure characteristics. The class activation mapping algorithm further revealed that the model consistently prioritized pore structure identification. The deep Taylor decomposition (DTD) algorithm extracted microstructure features that concentrated on the pore distribution near hydration products, where the GO groups exhibited denser and less continuous pore structure. Finally, a coefficient of variation matrix was employed to fuse micropores image data with DTD features data to generate typical pore probability distribution maps. Nanomodified pore structures exhibit discretized spatial distributions and lower overall pore probabilities, especially at low water-cement ratios. The established framework paves the way for intelligent, automated analysis of nanomodified microstructure, offering significant potential for future construction engineering applications of nanomaterials and deep learning technologies.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05694"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145718804","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}

{"title":"High-strength self-compacting concrete incorporating red mud: Development and comprehensive performance evaluation","authors":"Mohamed Inayathulla ,&nbsp;Shamsad Ahmad ,&nbsp;Tuba Iqbal ,&nbsp;Mohammed A. Al-Osta ,&nbsp;Syed K. Najamuddin ,&nbsp;Asad Hanif","doi":"10.1016/j.cscm.2025.e05714","DOIUrl":"10.1016/j.cscm.2025.e05714","url":null,"abstract":"<div><div>In this paper, red mud (RM), a highly alkaline waste material from aluminum production rich in alumina, iron, and silica, is used as a supplementary cementing material in developing high-strength self-compacting concrete (HS-SCC). The resulting fresh and hardened-state properties were determined. RM was added to HS-SCC in varying amounts to replace the cement. The results indicate that replacing cement with RM enhances the cohesiveness and flowability of SCC with improved mechanical and durability properties, due to its finer gradation and pozzolanic activity. The in-depth microstructural analysis by SEM showed enhanced packing density, densified pore structure, and interfacial strengthening. The optimal dosage of RM was determined as 10 %, leading to the 28-day compressive strength of the developed SCC &gt; 57 MPa. The RM replacement at 30 % also significantly improved resistance against acid attack and water penetration, while the corresponding drying shrinkage was lower with improved stress-strain behavior. The enhanced properties are primarily due to greater strength and elastic modulus. These findings highlight the use of RM as a viable, sustainable cement substitute that can help resource conservation and environmental remediation in producing high-strength, high-performance self-compacting concrete.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05714"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145788419","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}

{"title":"Development and field based validation of a predictive model for concrete compressive strength using fresh state properties in a large scale construction project","authors":"Geovanny Solano-Vinueza ,&nbsp;Jorge Albuja-Sánchez","doi":"10.1016/j.cscm.2025.e05705","DOIUrl":"10.1016/j.cscm.2025.e05705","url":null,"abstract":"<div><div>Estimation of a compressive strength of concrete earlier than for a standard 28 day test remains a highly challenging issue in construction industry on a large scale, where the quality control is merged with efficient scheduling and sustainable construction. This work presents a predictive model validated under real field conditions, through the processing of data collected in 4872 concrete cylinders produced in an infrastructure work with a total cast volume of 25,000 m³. The models are based on fresh state parameters temperature, slump, air content, and density that are commonly tested in the field, and are used to predict 7 and 28 days compressive strength for 35 and 40 MPa designs. Selected were three statistical methods including multiple linear regression as the base method, principal component analysis for dimensionality reduction, and LASSO regularization with interaction terms. Cross validation results showed the robust performance and the adjusted R² value was as high as 0.71 and RMSE was less than 3.4 MPa. While LASSO tightened model parsimony and did not reduce prediction efficiency, PCA increased precision in the context of multicollinearity and only slightly at the cost of precision. A strong correlation between early and late strength (0.84 and 0.74 for 35 MPa and 40 MPa, respectively) supports the use of early age results as practical predictors. The compressive strength prediction module was validated with real project data, providing ±RMSE confidence bands for operational use. These findings demonstrate that statistical modeling can be integrated into quality control workflows, enabling data driven decisions in concrete production and placement.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05705"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145788420","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}

{"title":"A developed SBS vitrimer for asphalt modification: Synergistic self-healing and aging resistance via dynamic covalent crosslinking","authors":"Guowei Hu ,&nbsp;Ruiqi Chen ,&nbsp;Zhifei Tan ,&nbsp;Xueliang Jiang ,&nbsp;Zhen Leng","doi":"10.1016/j.cscm.2025.e05679","DOIUrl":"10.1016/j.cscm.2025.e05679","url":null,"abstract":"<div><div>This study develops a styrene-butadiene-styrene (SBS) vitrimer via disulfide bond-mediated dynamic covalent crosslinking to address the inherent aging susceptibility and non-healing properties of conventional SBS in asphalt modification. Epoxidized SBS (eSBS) was synthesized and crosslinked with 4,4′-dithiodibutyric acid (DTBA) to construct covalent adaptable networks. Fourier-transform infrared spectroscopy (FTIR) confirmed successful vitrimer formation through ester bond formation (1734 cm⁻¹ peak). Optical microscopy revealed rapid self-healing behavior in the optimized SBS vitrimer (SV3, 0.3 ‰ DTBA of the butadiene structural units in SBS), with surface notches fully closing within 50 min at 90 °C, whereas unmodified SBS exhibited no healing under identical conditions. Thermogravimetric analysis demonstrated comparable thermal stability between SV3 and pristine SBS, with maximum degradation temperatures (T_max) near 463 °C. Mechanically, SV3 achieved a 25 % increase in tensile strength while retaining 63 % elongation relative to SBS, along with 100 % creep recovery at 80–100 °C, contrasting with irreversible deformation in unmodified SBS. Aging resistance was evaluated via Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV) tests. The SV3-modified binder (SV3mB) outperformed conventional SBS-modified binder (SBSmB), showing 54–58 % higher elastic recovery (<em>R</em>-value) and 19–20 % lower non-recoverable creep compliance (<em>J</em>_<em>nr</em>) post-RTFO aging. After PAV aging, SV3mB exhibited 46–105 % higher <em>R</em>-values and 62–70 % lower <em>J</em>_<em>nr</em> values. A healing index (<em>H</em>), derived from viscoelastic continuum damage (VECD) theory, quantified self-healing efficiency, revealing SV3mB’s superior damage mitigation under high strain (25 %–30 %) and extended fatigue life (<em>N</em>_<em>f</em>) due to dynamic bond exchange. These results demonstrate that SBS vitrimers enhance asphalt binder durability, aging resistance, and autonomous repair capabilities, offering transformative potential for pavement materials in extreme environmental conditions.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05679"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145788506","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}

{"title":"Long-term performance and RSM-based optimization of fly-ash/bentonite synchronous grout for undersea shield tunnels","authors":"Mujeeb ur Rehman ,&nbsp;Chao Liu ,&nbsp;Hai Liu ,&nbsp;Jie Cui ,&nbsp;Pei Wang ,&nbsp;Wei Chen","doi":"10.1016/j.cscm.2025.e05707","DOIUrl":"10.1016/j.cscm.2025.e05707","url":null,"abstract":"<div><div>High-performance synchronous grouts are crucial for the watertightness and long-term serviceability of undersea shield-driven tunnels, and their mixing design remains largely empirical. This study combined an extensive laboratory campaign with response surface methodology (RSM) to develop a statistically optimized grout. Class F fly ash (0–25 wt%) and sodium bentonite (0–7.5 wt%) were used as additives to Portland cement. Initially, 30 mixes were assessed to determine the dosage of water and superplasticizer. Subsequently, 24 mixes were prepared with varying fly ash and bentonite ratios to assess the fresh properties (flow cone time, mini slump, table spread, and bleeding), compressive strength (28, 90, 180, and 360 days), scour resistance, and marine durability (water absorption, electrical resistivity, sorptivity, mass loss, and chloride penetration after immersion in synthetic seawater). Second-order RSM models (R² ≥ 0.97) accurately captured eight response variables and revealed strong fly ash–bentonite interactions: fly ash improved the long-term strength and chloride resistance, whereas bentonite suppressed bleeding but increased viscosity. Optimization identified 20 % fly ash and 4 % bentonite at a water-to-cement ratio (w/c) of 0.35 as the best compromise between workability and durability. The predicted mix achieved a 28-day strength of 75.95 MPa. The validation tests showed deviations of less than 5 % from the RSM predictions. Compared to the control group, mass loss and chloride ingress at 360 d were reduced by 81.4 % and 47.6 %, respectively. The resulting design charts and regression equations provide tunnel engineers with a data-driven tool for customizing synchronous grouts that meet stringent long-term performance requirements of tunnel boring machines.</div></div>","PeriodicalId":9641,"journal":{"name":"Case Studies in Construction Materials","volume":"24 ","pages":"Article e05707"},"PeriodicalIF":6.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145788509","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}