Zhang Kunpeng, Wu Weijun, Fan Jiahui, Yuan Chengfang
Shanghai Highway and Bridge (Group) Co., Ltd., Shanghai 200433, China.
College of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China.
Materials (Basel). 2024 Aug 30;17(17):4307. doi: 10.3390/ma17174307.
This study investigates the potential use of Yellow River sand (YRS) sourced from the lower reaches of the Yellow River in China as a sustainable and cost-effective substitute for quartz sand in Engineered Cementitious Composites (ECC). With an annual accumulation of approximately 400 million tons in this region, YRS presents a substantial resource. ECC specimens with 100% YRS replacement with quartz sand were subjected to various curing methods: natural, steam, standard, and sprinkler. Extensive mechanical testing including flexural, compressive, uniaxial tensile, and four-point flexural tests was conducted. Additionally, Scanning Electron Microscope (SEM) and Mercury Intrusion Porosimetry (MIP) analyses investigated microscopic mechanisms influencing macroscopic mechanical properties. Finally, the mechanical properties of the YRS-ECC test block after 14 days of standard curing and the traditional sand ECC test block were compared and analyzed. The results indicate that ECC specimens with 100% YRS substitution under natural curing show an optimal ultimate tensile strain of more than 4%, providing the best resistance to the reduction in ultimate flexural load and deflection due to aging. Steam curing enhances flexural and compressive strength, achieving an ultimate flexural load of 5 kN and a maximum deflection of 4.42 mm at 90 days. SEM analysis revealed lower C-S-H gel density under natural curing and higher under steam curing, enhancing fiber pull-out in steam-cured specimens. The MIP tests demonstrated that natural curing had the highest porosity (32.86%) and average pore size (51.69 nm), whereas steam curing resulted in the smallest average pore size, with 44% of pores under 50 nm. Compared with traditional sand, it is found that the ultimate bending load and deflection of YRS-ECC are 5.7% and 9.4% higher than those of traditional sand ECC, respectively, and its ultimate tensile strength and strain are also improved. These findings highlight YRS as a sustainable alternative to natural sand in ECC, with natural curing proving the most effective for superior mechanical performance, including tensile strain, crack resistance, and durability.
本研究探讨了源自中国黄河下游的黄河砂（YRS）作为工程水泥基复合材料（ECC）中石英砂的可持续且经济高效替代品的潜在用途。该地区每年约有4亿吨的堆积量，黄河砂是一种丰富的资源。用黄河砂完全替代石英砂的ECC试件采用了多种养护方法：自然养护、蒸汽养护、标准养护和喷水养护。进行了包括弯曲、压缩、单轴拉伸和四点弯曲试验在内的广泛力学测试。此外，通过扫描电子显微镜（SEM）和压汞孔隙率测定法（MIP）分析研究了影响宏观力学性能的微观机制。最后，对标准养护14天后的黄河砂-ECC试块和传统砂ECC试块的力学性能进行了比较和分析。结果表明，自然养护下用黄河砂完全替代的ECC试件显示出超过4%的最佳极限拉伸应变，在抵抗因老化导致的极限弯曲荷载和挠度降低方面表现最佳。蒸汽养护提高了弯曲强度和抗压强度，在90天时达到了5 kN的极限弯曲荷载和4.42 mm的最大挠度。SEM分析表明，自然养护下C-S-H凝胶密度较低，蒸汽养护下较高，这增强了蒸汽养护试件中的纤维拔出。MIP试验表明，自然养护的孔隙率最高（32.86%），平均孔径最大（51.69 nm），而蒸汽养护的平均孔径最小，50 nm以下的孔隙占44%。与传统砂相比，发现黄河砂-ECC的极限弯曲荷载和挠度分别比传统砂ECC高5.7%和9.4%，其极限抗拉强度和应变也有所提高。这些发现突出了黄河砂作为ECC中天然砂的可持续替代品的地位，自然养护被证明对包括拉伸应变、抗裂性和耐久性在内的优异力学性能最为有效。
