不同纤维大坝混凝土的变形性能和抗裂性分析

Analysis on Deformation and Anti-cracking Properties of Dam Concrete Mixed with Different Kinds of Fibers

选用PVA1、PVA2和PP三种不同厂家生产的纤维,通过试验研究了纤维对大坝混凝土力学性能和变形性能的影响,并对混凝土抗裂性进行了分析。结果表明,掺入三种纤维后混凝土的抗压强度、劈拉强度和轴拉强度均不同程度地降低;与基准混凝土相比,纤维混凝土干缩值均略有增加,自生体积变形收缩减小,且180 d龄期后纤维混凝土的变形均由微收缩型转变为微膨胀型,表明纤维可以抑制混凝土的自生体积收缩,有利于提高混凝土的抗裂性能;各加荷龄期PVA1纤维混凝土的徐变均大于相应基准混凝土,PVA2和PP纤维混凝土的徐变小于或等于基准混凝土;不同纤维对大坝混凝土抗裂性的改善效果不同,本研究采用的PVA1纤维对抗裂性的改善作用最优。在工程具体应用时需结合试验进行纤维材料优选。

Three kinds of fibers of PVAI, PVA2 and PP from different manufacturers are selected in the study on the mechanical and deformation properties of dam concrete. It is indicated that the compressive strength, splitting tensile strength and axial tensile strength of dam concrete with these three kinds of fibers are all decreased to a varying degree when compared with reference concrete. On the other hand, the dry shrinkage of fiber-reinforced concrete is somewhat increased, while the autogenous volumetric shrinkage is decreased, which suggests that the fibers can restrain the autogenous volumetric shrinkage of dam concrete and consequently improve its anti-cracking properties. At different loading ages, the creep of concrete with fiber PVA1 is higher than that of reference concrete, while the creeps of concrete with PVA2 and PP are less than or almost equal to that of reference concrete. The improvement effects of different fibers on anti-cracking properties of dam concrete are varying. In this study, the effect of fiber PVA1 is best, which prompts that the optimization experiments on fibers should be carried out according to actual project conditions.