Case Studies in Construction Materials最新文献

Theory and methodology for testing asphalt mixtures’ tensile strength by four-point bending 四点弯曲试验沥青混合料抗拉强度的理论和方法

IF 6.6 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Case Studies in Construction Materials

Pub Date : 2026-07-01 Epub Date: 2025-12-20 DOI: 10.1016/j.cscm.2025.e05722

Jun Zhang , Xinyu Zhang , Shouxin Wang , Shufang Li , Wuju Wei

Tensile strength is a crucial parameter for assessing the pavement performance of asphalt mixtures. However, the methods currently commonly used to test the tensile strength of asphalt mixtures usually encounter issues related to operational convenience and testing theory, which significantly impact the accuracy and ease of conducting tensile strength tests. Therefore, this paper proposed a novel testing theory and methodology that utilizes the actual tensile stress–strain relationship of asphalt mixtures and the measured neutral axis height of asphalt mixture bending beams of four-point bending test to determine the tensile strength of the mixture. Furthermore, a series of four-point bending beam tests and direct tension tests at various loading rates were conducted to validate this method. The results demonstrated that this method effectively overcomes the limitations of conventional testing method, and the tensile strength determined by this approach is aligned well with that obtained from direct tension tests, their percent error is only −30 %∼20 %. Additionally, this method better reflects the tensile performance of the mixture over a broad section of the beam, ensuring representative and reliable test results.

抗拉强度是评价沥青混合料路用性能的重要参数。然而，目前常用的沥青混合料抗拉强度测试方法往往存在操作方便性和测试理论等问题，严重影响了抗拉强度测试的准确性和易用性。因此，本文提出了一种新的测试理论和方法，利用沥青混合料的实际拉伸应力-应变关系和四点弯曲试验中测量到的沥青混合料弯曲梁中性轴高度来确定混合料的抗拉强度。此外，还进行了不同加载速率下的四点弯梁试验和直拉试验，验证了该方法的有效性。结果表明，该方法有效地克服了传统测试方法的局限性，所测得的拉伸强度与直接拉伸试验结果吻合良好，两者的百分比误差仅为−30 % ~ 20 %。此外，该方法更好地反映了混合料在梁的宽截面上的拉伸性能，确保了代表性和可靠的测试结果。

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引用次数: 0

Coupled mechanical-microstructural damage behavior of phosphoric acid-modified MOC under dry-wet-freeze-thaw cycling 干湿-冻融循环下磷酸改性MOC的力学-微观结构耦合损伤行为

IF 6.6 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Case Studies in Construction Materials

Pub Date : 2026-07-01 Epub Date: 2025-12-17 DOI: 10.1016/j.cscm.2025.e05693

Jian Gong , Jiaxuan Zhang , Shuren Wang , Aichi Ma , Zhenzhen An

To address the drawbacks of magnesium oxychloride cement (MOC), phosphoric acid was employed to modify MOC cement. MOC cement exhibits poor water resistance, and in cold regions, it is subjected to a complex, multi-stress environment that significantly exacerbates its poor water resistance. Modifying MOC cement can improve its water resistance and thereby enhance its stability in cold regions. This experiment adopted a multi-scale design to simulate temperature variations in cold regions and investigated the effects of dry-wet-freeze-thaw (DWFT) cycle coupling on MOC cement. Mechanical strength, mineral composition, microstructural changes, and pore distribution were analyzed through uniaxial compressive strength (UCS) testing, X-ray diffraction (XRD), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR). Damage analysis was conducted on the test specimens based on the test results. The findings revealed that the strength loss of unmodified MOC exceeded 50 % after 20 DWFT cycles, whereas the strength of modified MOC increased by approximately 40 %. The addition of phosphoric acid prevented the dissolution of phase 5 crystals in the MOC system, and the porosity of the modified MOC cement decreased by about 50 %. A damage equation for specimens under DWFT cycles was derived and validated, enabling quantitative analysis of the impact of modifiers on MOC cement performance. The research findings hold significant importance for studying the durability and modification of MOC cement.

针对氯氧镁水泥（MOC）存在的缺陷，采用磷酸对MOC水泥进行改性。MOC水泥的耐水性较差，在寒冷地区，其经受复杂的多应力环境，显著加剧了其耐水性差。改性MOC水泥可以提高其耐水性，从而增强其在寒冷地区的稳定性。本试验采用多尺度设计模拟寒冷地区温度变化，研究干湿冻融（DWFT）循环耦合对MOC水泥的影响。通过单轴抗压强度（UCS）测试、x射线衍射（XRD）、扫描电镜（SEM）和核磁共振（NMR）等手段分析了机械强度、矿物组成、微观结构变化和孔隙分布。根据试验结果对试件进行损伤分析。结果表明，经过20次DWFT循环后，未改性MOC的强度损失超过50% %，而改性MOC的强度增加了约40% %。磷酸的加入阻止了MOC体系中5相晶体的溶解，改性MOC水泥的孔隙率降低了约50% %。推导并验证了DWFT循环下试件的损伤方程，从而定量分析了改性剂对MOC水泥性能的影响。研究结果对MOC水泥的耐久性和改性研究具有重要意义。

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引用次数: 0

Enabling recycled coarse aggregates in ductile ECC: A synergistic enhancement of mechanical and sustainability properties 使再生粗骨料在延性ECC：机械和可持续性性能的协同增强

IF 6.6 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Case Studies in Construction Materials

Pub Date : 2026-07-01 Epub Date: 2025-12-19 DOI: 10.1016/j.cscm.2025.e05719

Yichao Wang , Zeen Hu , Sisi Feng , Yayun Qin , Haitao Yang , Guowen Sun , Yao Zhang

To meet the micro-mechanical design guidelines for achieving strain hardening and steady-state cracking behavior, the coarse aggregates are conventionally excluded from engineered cementitious composite materials. The absence of coarse aggregates leads to challenges, including enormous carbon emissions, elevated drying shrinkage, and reduced compressive strength. To overcome these limitations, this study explored the development of a novel ultra-high ductile concrete (UHDC) incorporating coarse aggregates, with the particular focus on the recycled coarse aggregates. The effects of coarse aggregate content (16 %, 20 % and 24 %) on the workability, drying shrinkage, and basic mechanical properties of UHDC were systematically investigated through the physical and mechanical tests. The results demonstrated that all the UHDC mixtures, both with natural and recycled coarse aggregates, consistently exhibited strain-hardening behavior and multiple micro-cracking characteristics. All the mixtures achieved the average tensile strains exceeding 5 %, while maintaining crack width below 150 μm. As the coarse aggregate content increased, the workability, drying shrinkage, tensile strength, and tensile strain exhibited progressive reduction, whereas the compressive strength demonstrated significant enhancement. Notably, compared to the mixture without coarse aggregates, UHDC containing 24 % coarse aggregates markedly reduced the 28-day shrinkage strain by 65.83 % to 450.56 µε, while simultaneously enhancing the compressive strength by 28.4 %, reaching 38.9 MPa. Furthermore, scanning electron microscopy and X-ray computed tomography (CT) tests were conducted to analyze the micro-structural and pore structure characterization, respectively. In addition, the study demonstrated that compared to the mixture without coarse aggregates, UHDC containing 24 % recycled coarse aggregates significantly reduced the energy consumption and carbon emissions by 18.38 % and 25.25 %, respectively. It was preliminary verified that the incorporation of coarse aggregate effectively enhanced the mechanical performance and promoted sustainability through waste concrete utilization.

为了满足实现应变硬化和稳态开裂行为的微力学设计准则，粗集料通常被排除在工程胶凝复合材料之外。缺乏粗骨料会带来挑战，包括大量的碳排放，干燥收缩率升高，抗压强度降低。为了克服这些限制，本研究探索了一种新型超高延性混凝土（UHDC）的发展，其中包括粗骨料，特别关注再生粗骨料。通过物理力学试验，系统研究了粗集料掺量（16 %、20 %和24 %）对UHDC和易性、干燥收缩率和基本力学性能的影响。结果表明，所有UHDC混合料，无论是天然粗骨料还是再生粗骨料，都表现出一致的应变硬化行为和多重微裂特征。所有混合物的平均拉伸应变均超过5 %，而裂纹宽度均保持在150 μm以下。随着粗集料掺量的增加，其和易性、干收缩率、抗拉强度和拉伸应变均呈递减趋势，而抗压强度则有显著提高。值得注意的是，与不含粗集料的混合料相比，含24 %粗集料的UHDC显著降低了28天收缩应变65.83 %至450.56µε，同时抗压强度提高28.4 %，达到38.9 MPa。通过扫描电子显微镜和x射线计算机断层扫描（CT）测试分别分析了微观结构和孔隙结构表征。此外，研究表明，与不含粗骨料的混合料相比，含有24% %再生粗骨料的UHDC可显著降低能耗和碳排放，分别降低18.38 %和25.25 %。初步验证了粗集料的掺入有效提高了废混凝土的力学性能，促进了废混凝土的可持续性。

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引用次数: 0

Improving the self-healing properties of bitumen mastic under microwave irradiation by heated oil-ground steel slag 加热油磨钢渣提高微波辐照下沥青胶泥的自愈性能

IF 6.6 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Case Studies in Construction Materials

Pub Date : 2026-07-01 Epub Date: 2025-12-23 DOI: 10.1016/j.cscm.2025.e05729

Qiao Liu , Jingyi Zeng , Xingyang He , Huahui Qi , Ying Su , Wei Chen , Chao Yang , Jin Yang , Chuang Zhou

Steel slag (SS) is a solid waste rich in iron elements with the potential for microwave heating. However, the low ferrite content and the barrier of the silicate layer limit the efficiency of microwave heating of SS. This study employs soybean oil as the grinding environment and utilizes heated oil milling technology to functionalize steel slag. This process facilitates the separation and purification of the iron phase from the SS, enabling the generation of additional Fe₃O₄ through reduction reactions. The synergistic effect of heating and grinding promotes the conversion of Fe^3 + to Fe²⁺, which results in a 31 % increase in Fe²⁺ content and a 34 % increase in saturation magnetization of heated oil grinding steel slag (HGSS). Through the targeted design of particle size and oleophilic surfaces, HGSS is uniformly and compactly dispersed in the bitumen, constructing a network structure with multi-refraction properties, which reduces the reflection loss by 26 %. Under the combined effect of phase and structural changes, compared to SS bitumen mastic, HGSS bitumen mastic showed a 20 % increase in temperature rise at 60 s of microwave heating, in addition to an 11 % increase in healing index. This study aims to enhance the microwave absorption performance of SS by optimizing its microstructure and composition, thereby improving the self-healing efficiency of steel slag-bitumen composite materials under microwave heating conditions and providing new insights into the high-value utilization of SS.

钢渣是一种富含铁元素的固体废物，具有微波加热的潜力。然而，铁素体含量低，硅酸盐层的阻隔性限制了微波加热SS的效率。本研究以大豆油为研磨环境，利用加热油磨技术对钢渣进行功能化处理。这个过程有利于从SS中分离和纯化铁相，使通过还原反应产生额外的Fe3O4成为可能。加热和磨矿的协同作用促进了Fe3 +向Fe2+的转化，使加热后的油磨钢渣中Fe2+含量提高了31 %，饱和磁化强度提高了34 %。通过对粒径和亲油表面的针对性设计，使HGSS均匀致密地分散在沥青中，形成具有多重折射特性的网状结构，使反射损失降低26% %。在相与结构变化的共同作用下，微波加热60 s时，HGSS沥青与SS沥青相比，温升提高了20 %，愈合指数提高了11 %。本研究旨在通过优化钢渣-沥青复合材料的微观结构和组成，增强其微波吸收性能，从而提高钢渣-沥青复合材料在微波加热条件下的自愈效率，为钢渣-沥青复合材料的高价值利用提供新的见解。

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引用次数: 0

Manganese zinc ferrite composite graphene oxide improves the macroscopic and microscopic properties of cement paste 锰锌铁氧体复合氧化石墨烯改善了水泥浆体的宏观和微观性能

IF 6.6 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Case Studies in Construction Materials

Pub Date : 2026-07-01 Epub Date: 2026-01-02 DOI: 10.1016/j.cscm.2025.e05751

Suhui Yu , Aoyang Li , Jian Yuan , Zhaoguang Li , Yan Wang , Shaohui Zhang

Graphene oxide (GO) had great potential in improving the performance of cement-based materials. However, the strong interaction between GO sheets was easy to cause agglomeration, which seriously limited the full play of its enhancement effect. To address this issue, this study proposed a novel strategy using manganese-zinc ferrite (MZF) to assist the dispersion of GO, aiming to solve the key problems of uneven dispersion and poor stability of GO in cement-based materials. In this study, MZF@GO materials with different composite ratios (MZF: GO = 2:1, 5:1, 10:1) were prepared. The dispersion behavior of MZF@GO was discussed. The effects of MZF@GO on the hydration process, macroscopic properties, and microstructure of cement composites were systematically studied. The results showed that MZF formed strong interfacial bonding with GO through chemical coordination, exhibiting excellent dispersion stability in simulated cement pore solution. After adding cement, MZF@GO accelerated the hydration heat release of cement, and the peak heat flow of MZF-5@GO was the highest (2.1 mW/g). Compared with the JZ group (curing 28 days), the compressive strength of MZF-2@GO, MZF-5@GO, and MZF-10@GO samples increased by 9.39 %, 16.18 %, and 8.87 %, respectively, while the flexural strength increased by 22.67 %, 32.86 % and 26.03 %, respectively. Meanwhile, the total porosity of the MZF-5@GO group decreased by about 13.26 %, indicating that the dispersed GO could effectively promote the growth of hydration products and reduce harmful pores, whereas MZF primarily contributed through physical filling. MZF@GO did not significantly reduce the resistivity of cement composites. Overall, MZF served as an effective dispersing medium for GO and provided a new approach for its efficient application in cement-based materials.

氧化石墨烯在改善水泥基材料性能方面具有很大的潜力。然而，氧化石墨烯片间的强相互作用容易造成团聚，严重限制了其增强效果的充分发挥。针对这一问题，本研究提出了一种使用锰锌铁氧体（MZF）辅助氧化石墨烯分散的新策略，旨在解决氧化石墨烯在水泥基材料中分散不均匀和稳定性差的关键问题。本研究制备了不同复合比例（MZF: GO = 2:1, 5:1, 10:1）的MZF@GO材料。讨论了MZF@GO的色散行为。系统研究了MZF@GO对水泥复合材料水化过程、宏观性能和微观结构的影响。结果表明，MZF与GO通过化学配位形成了强界面键合，在模拟水泥孔隙溶液中表现出优异的分散稳定性。加入水泥后，MZF@GO加速了水泥的水化热释放，其中MZF-5@GO的峰值热流最高（2.1 mW/g）。相比生理组(养护28天),MZF-2@GO的抗压强度,MZF-5@GO,和MZF-10@GO样本 %增加了9.39,16.18 %,和8.87 %,分别在挠曲强度增加了22.67 %,分别32.86 %和26.03 %。同时，MZF-5@GO组的总孔隙率降低了约13.26 %，说明分散的氧化石墨烯能够有效地促进水化产物的生长，减少有害孔隙，而MZF主要通过物理填充来贡献。MZF@GO并没有显著降低水泥复合材料的电阻率。综上所述，MZF作为一种有效的氧化石墨烯分散介质，为其在水泥基材料中的高效应用提供了新的途径。

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引用次数: 0

Composite rejuvenator strategy for optimizing the performance of RAP-recycled asphalt mixtures 优化rap -再生沥青混合料性能的复合再生剂策略

IF 6.6 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Case Studies in Construction Materials

Pub Date : 2026-07-01 Epub Date: 2026-01-06 DOI: 10.1016/j.cscm.2026.e05773

Zeng Guodong , Guo Yuchen , Li Hao , Liu Mingyan , Fang Yang , Wang Xuancang , Tian Yuan

Asphalt pavement recycling is increasingly recognized as an effective strategy for resource conservation and carbon reduction. This study investigates the deterioration characteristics of aged asphalt and develops a composite rejuvenator composed of bio-oil and DOTP plasticizer to restore binder performance and enhance the pavement properties of RAP-recycled asphalt mixtures. Response surface methodology was used to optimize rejuvenator dosage, after which recycled mixtures with RAP contents of 15 %, 30 %, 45 %, and 60 % were fabricated. Binder tests, high- and low-temperature rheological evaluations, rutting tests, moisture stability tests, freeze-thaw splitting, and semicircular bending (SCB) tests were conducted to assess rejuvenation effectiveness. The optimized formulation (M2: 3 % bio-oil + 2.5 % DOTP) achieved a 93 % recovery rate of binder properties and exhibited rheological behavior most comparable to virgin asphalt, showing improved high-temperature stability, enhanced low-temperature relaxation, and increased mixture fracture energy. Grey relational analysis revealed that RAP content exerted the greatest influence on stiffness-related indicators and negatively affected crack resistance, with 30 % RAP achieving the best balance among performance metrics. Overall, the bio-oil - DOTP composite rejuvenator effectively improved the high-temperature, low-temperature, and moisture-resistant performance of RAP-recycled asphalt mixtures, providing a practical pathway for promoting sustainable asphalt recycling.

沥青路面回收利用作为一种节约资源、减少碳排放的有效策略，越来越受到人们的重视。研究了老化沥青的劣化特性，研制了由生物油和DOTP增塑剂组成的复合再生剂，以恢复rap -再生沥青混合料的粘结剂性能，提高其路用性能。采用响应面法优化回春剂用量，制备RAP含量分别为15 %、30 %、45 %和60 %的回春剂。通过粘合剂试验、高温和低温流变学评价、车辙试验、水分稳定性试验、冻融劈裂和半圆弯曲（SCB）试验来评估回复性效果。优化后的配方（M2: 3 %生物油+ 2.5 % DOTP）获得了93 %的粘结剂性能回收率，并表现出与原始沥青最相似的流变行为，表现出更好的高温稳定性，增强的低温弛豫，增加了混合料的断裂能。灰色关联分析表明，RAP含量对刚度相关指标的影响最大，对抗裂性能的影响为负，其中30% % RAP在性能指标之间达到最佳平衡。总体而言，生物油- DOTP复合再生剂有效提高了rap再生沥青混合料的高温、低温、耐湿性能，为促进沥青可持续再生提供了一条切实可行的途径。

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引用次数: 0

Experimental study on the bonding strength of rebars in seawater sea-sand concrete under chloride erosion and freeze–thaw cycles 氯离子侵蚀和冻融循环作用下海水海砂混凝土中钢筋粘结强度试验研究

IF 6.6 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Case Studies in Construction Materials

Pub Date : 2026-07-01 Epub Date: 2026-01-03 DOI: 10.1016/j.cscm.2026.e05754

Yao Xiao, Yiwen Qu, Siyuan Wang, Jianghao Liu

This study experimentally investigated the bond behavior between reinforcement and seawater sea-sand concrete (SSC) under the combined actions of chloride-induced corrosion and freeze–thaw (F–T) cycles. The coupled environmental effects were simulated through a slow freezing test and an accelerated electrification corrosion method. In the test program, the number of F–T cycles (0, 15, 25, and 50) and the chloride ion concentrations (3.5 %, 7 %, and 10 %) were used as key environmental variables. The bond–slip behavior between rebars and SSC was then examined by push-out tests, taking into account the F–T cycles, salt solution concentration, rebar type (plain and deformed), and concrete strength grades. The results achieved in this study indicate that the interfacial bond strength between the rebars and SSC decreased with the increase in F-T cycles. After 50 F–T cycles, the bond strength of the specimens was reduced by more than 19 % compared with that of the uncycled specimens. The variation trend of bond properties of specimens under the coupling effect of F-T cycles and chloride corrosion was related to the F-T cycles. The bonding slip strength exhibited a pattern of initial increase followed by a gradual decline with increasing F-T cycles. Finally, A theoretic bond-slip curve between rebars and SSC after chloride salt F-T cycles is proposed and is in good agreement with the experimental results.

试验研究了氯化物腐蚀和冻融循环共同作用下海水海砂混凝土（SSC）与钢筋的粘结行为。通过慢冻结试验和加速电蚀法模拟了环境耦合效应。在测试程序中，以F-T循环次数（0、15、25和50）和氯离子浓度（3.5 %、7 %和10 %）作为关键环境变量。然后，考虑到F-T循环、盐溶液浓度、钢筋类型（普通和变形）以及混凝土强度等级，通过推出试验检查了钢筋与SSC之间的粘结滑移行为。研究结果表明，随着F-T循环次数的增加，钢筋与SSC之间的界面结合强度降低。经过50次F-T循环后，与未循环的试件相比，试件的粘结强度降低了19. %以上。在F-T循环和氯化物腐蚀耦合作用下，试件粘结性能的变化趋势与F-T循环有关。随着F-T循环次数的增加，粘结滑移强度呈现先增加后逐渐下降的规律。最后，提出了氯盐F-T循环作用下钢筋与SSC粘结滑移的理论曲线，该曲线与试验结果吻合较好。

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引用次数: 0

Preparation and performance evaluation of aluminum sulfate-based alkali-free suspension accelerators for shotcrete 喷射混凝土用硫酸铝基无碱悬浮促进剂的制备及性能评价

IF 6.6 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Case Studies in Construction Materials

Pub Date : 2026-07-01 Epub Date: 2026-01-05 DOI: 10.1016/j.cscm.2026.e05766

Shuncheng Xiang , Yutao Zou , Jie Chen , Xin Yang , Yingli Gao , Yuelin Li , Jing Zhang , Zhen Jiang , Zheng Len , Yanqi He , Yang Liu , Jingping Zhang , Jing Zhang

An aluminum sulfate-based alkali-free suspension rapid-setting agent (AF-LX-FSA) was formulated, which exhibited optimal performance at a dosage of 8 % by mass of cementitious materials. At the optimal dosage, the agent achieved a flowability of 135 mm, remarkably short initial and final setting times of 2.86 min and 4.67 min, and high compressive strengths of 1.06 MPa, 13.2 MPa, and 49 MPa at 6 h, 1 d, and 28 d, respectively, all conforming to the Chinese national standard GB/T 35159–2017. The acceleration mechanism and microstructural evolution were systematically investigated via XRD, TG-DTG, and SEM, revealing that the rapid setting and early strength development were primarily attributed to the rapid formation of a dense network of ettringite (AFt) crystals. The insights into the acceleration mechanism and microstructure provide a valuable theoretical basis for the development of high-performance suspension alkali-free accelerators.

配制了一种硫酸铝基无碱悬浮速凝剂（AF-LX-FSA），当胶凝材料质量比为8 %时，其性能最佳。在最佳掺量下，该药剂的流动性为135 mm，初凝时间为2.86 min，终凝时间为4.67 min，在6 h、1 d和28 d时的抗压强度分别为1.06 MPa、13.2 MPa和49 MPa，均符合中国国家标准GB/T 35159-2017。通过XRD、TG-DTG和SEM对加速机制和微观组织演化进行了系统研究，结果表明，快速凝固和早期强度发展主要是由于快速形成密集的钙矾石（AFt）晶体网络。对加速机理和微观结构的深入了解，为开发高性能悬浮型无碱加速剂提供了有价值的理论依据。

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引用次数: 0

Clay activation through CO2-derived oxalic acid for advancing its reactivity and strength of limestone calcined clay cement (LC3) 二氧化碳衍生草酸活化粘土提高石灰石煅烧粘土水泥（LC3）的反应性和强度

IF 6.6 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Case Studies in Construction Materials

Pub Date : 2026-07-01 Epub Date: 2025-12-11 DOI: 10.1016/j.cscm.2025.e05684

Miral Fatima , Mounir Ltifi , Khuram Rashid , Idrees Zafar

The widespread deployment of limestone calcined clay cement (LC³) is constrained by its dependence on high-grade kaolinitic clays. Abundant, low-grade clays often exhibit poor pozzolanic reactivity and require tailored activation strategies. This study proposes a novel clay activation approach using oxalic acid, an organic acid producible through electrochemical CO₂ reduction utilizing a waste carbon stream, for the development of LC³. Three activation regimes were examined: thermal activation (TH), thermal followed by oxalic acid immersion (TI), and co-calcination with oxalic acid (CT). Comprehensive characterization (XRF, QXRD, R³) reveals that the CT method uniquely enhances reactivity by promoting selective leaching of Fe₂O₃ and enriching Al₂O₃ content, while also inducing mineralogical transitions from quartz to more reactive phases like cristobalite. The R³ test confirmed CT’s superiority, showing the highest bound water content (14.4 %) and showed a significant correlation with strength at all ages (correlation co-efficient ranging from 0.89 to 0.94). In LC³ binders, CT-activated clay yielded a more balanced hydration phase assemblage, accelerating early-age hydration. This translated directly to superior mechanical performance; LC³-CT blends nearly met the ASTM strength criterion (i.e., 42.5 MPa) benchmark at 28 days (within 1 % deviation), significantly outperforming LC³-TH blends (10 % deficit). Despite the added acid, the LC³-CT system maintains a compelling environmental advantage, achieving 21–23 % reductions in CO₂ emissions compared to OPC, alongside cost savings of 8–11 %. Results establish CT activation as a technically superior and environmentally sustainable pathway for valorizing low-grade clays. By simultaneously enhancing reactivity and leveraging CO₂ utilization, this approach strengthens the foundation for next-generation, low-carbon cement technologies.

石灰石煅烧粘土水泥（LC3）的广泛应用受到其对高岭石粘土的依赖的限制。丰富的低品位粘土通常表现出较差的火山反应性，需要定制活化策略。本研究提出了一种新的粘土活化方法，利用草酸（一种有机酸，通过利用废碳流电化学CO2还原产生）来开发LC3。研究了三种活化方式：热活化（TH）、热后草酸浸（TI）和草酸共烧（CT）。综合表征（XRF， QXRD, R3）表明，CT方法通过促进Fe2O3的选择性浸出和富集Al2O3含量，同时诱导矿物从石英向方石英等更具反应性的相转变，从而独特地提高了反应性。R3测试证实了CT的优势，显示出最高的束缚水含量（14.4 %），并且在所有年龄段都与强度具有显著的相关性（相关系数范围为0.89 ~ 0.94）。在LC3粘合剂中，ct活化粘土产生了更平衡的水化相组合，加速了早期水化。这直接转化为优越的机械性能；LC3-CT共混物在28天内几乎达到ASTM强度标准（即42.5 MPa）基准（偏差在1 %以内），显著优于LC3-TH共混物（偏差为10 %）。尽管添加了酸，LC3-CT体系仍保持着令人信服的环境优势，与OPC相比，二氧化碳排放量减少了21 - 23% %，成本节省了8 - 11% %。结果表明，连续油管活化是一种技术上优越、环境上可持续的低品位粘土活化途径。通过同时提高反应性和利用二氧化碳，这种方法为下一代低碳水泥技术奠定了基础。

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引用次数: 0

Push-off tests and comparative evaluation of direct shear transfer behavior in normal, steel fiber-reinforced, and ultra-high-performance concrete 普通混凝土、钢纤维增强混凝土和超高性能混凝土的推离试验和直接剪切传递行为的比较评价

IF 6.6 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Case Studies in Construction Materials

Pub Date : 2026-07-01 Epub Date: 2025-12-15 DOI: 10.1016/j.cscm.2025.e05703

Qing Zhi , Guodong Zhang , Liqun Kang

This study investigates the direct shear behavior of normal concrete (NC), steel fiber–reinforced concrete (SFRC), and ultra–high–performance concrete (UHPC) through a systematic experimental program. Forty large–scale Z–shaped push–off specimens were tested under monotonic shear loading, with variations in fiber content, lateral confinement, reinforcement ratio, initial crack width, lap splice length, and reinforcement grade. Test results revealed that steel fibers significantly enhanced post–cracking resistance, residual strength, and energy dissipation, while lateral confinement and transverse reinforcement effectively limited slip and stabilized shear transfer. UHPC specimens exhibited superior shear capacity and stiffness, even with reduced lap splice lengths, establishing a clear performance hierarchy (UHPC > SFRC > NC) owing to their dense matrix and enhanced bond. Five performance indices—initial stiffness, peak shear strength, slip at peak, residual strength, and energy dissipation—were proposed for consistent evaluation, and regression–based sensitivity analysis highlighted the dominant roles of material type (especially UHPC), confinement, and reinforcement ratio. Furthermore, a unified regression–based shear strength expression was established, integrating cohesion, friction, reinforcement clamping, and fiber bridging, and achieved high predictive accuracy across all 40 specimens. Overall, the findings clarify the distinct contributions of NC, SFRC, and UHPC to shear transfer mechanisms and provide a unified expression and rational guidelines for the design of precast and composite joints in advanced concrete structures.

本研究通过系统的试验程序研究了普通混凝土（NC）、钢纤维增强混凝土（SFRC）和超高性能混凝土（UHPC）的直剪性能。在单调剪切荷载作用下，对40个大型z形推断试件进行了纤维含量、侧约束、配筋率、初始裂缝宽度、搭接长度和配筋等级的变化试验。试验结果表明，钢纤维显著提高了混凝土的抗裂后强度、残余强度和耗能能力，而横向约束和横向加固有效地限制了混凝土的滑移和稳定了剪切传递。UHPC试件表现出优异的抗剪能力和刚度，即使搭接长度减少，由于其致密的基体和增强的粘结，建立了明确的性能等级（UHPC > SFRC >； NC）。提出了五个性能指标——初始刚度、峰值抗剪强度、峰值滑移、残余强度和能量耗散——以进行一致性评估，基于回归的敏感性分析强调了材料类型（尤其是超高强度混凝土）、约束和配筋率的主导作用。此外，建立了一个统一的基于回归的抗剪强度表达式，整合了黏聚力、摩擦、钢筋夹紧和纤维桥接，并在所有40个试件中实现了较高的预测精度。总体而言，研究结果阐明了NC、SFRC和UHPC对剪切传递机制的不同贡献，并为高级混凝土结构中预制和组合节点的设计提供了统一的表达和合理的指导。

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引用次数: 0