低成本PVA纤维对超高韧性水泥基复合材料力学性能的影响

EFFECT OF LOW-COST PVA FIBERS ON THE MECHANICAL PROPERTIES OF ENGINEERED CEMENTITIOUS COMPOSITES

超高韧性纤维增强水泥基复合材料(ECC)因其出色的高韧性及多缝开裂特性备受关注,然而一直以来因配比中进口PVA纤维的使用导致高昂的价格限制了其在工程中的大规模应用。为了进一步降低成本及实现原材料的本土化,研究低成本国产PVA纤维对ECC力学性能的影响十分必要。通过单轴拉伸、压缩、三点抗弯及单裂缝拉伸等宏观、细观试验研究两种国产低成本PVA-ECC的力学性能,并借助纤维分散性试验及SEM,探讨纤维的分散等微观特征。结果表明,低成本国产纤维在基体中具有良好的分散性,尽管其纤维桥接余能、最大桥接应力及PSH指数低于进口纤维,但均能满足能量与强度准则,即便相对较差的纤维A试件的3 d、7 d及28 d的极限拉伸应变也可达到2.52%、3.34%及3.08%,可实现良好的应力硬化行为及饱和多缝开裂特性,满足ECC的使用要求。

Engineered Cementitious Composites(ECC) have attracted much attention because of its high toughness and multiple cracking characteristics. However, the use of imported PVA fibers in the past has resulted in high price which limited large scale engineering applications. To reduce the cost and achieve the localization of raw materials, it is necessary to study the influence of low-cost domestic PVA fibers on the mechanical properties of ECCs. The mechanical properties of two kinds of domestic low-cost PVA-ECCs were studied by macroscopic and mesoscopic experiments, including uniaxial tensile, compression, three-point bending and single-crack tensile tests. The microscopic features such as the fiber dispersion was investigated by the tests and SEM. The results show that the low-cost domestic fibers have good dispersibility in the matrix. Although the fiber bridging complementary energy, maximum bridging stress and the PSH index are lower than those of imported fibers, they meet the energy and strength criteria. The tensile strain capacity of the relatively poor fiber A reached 2.52%, 3.34% and 3.08% at 3 d, 7 d and 28 d, respectively, which exhibited good stress hardening behavior and saturated multi-cracking characteristics and satisfies the application requirements of ECC.