高延性水泥基复合材料高温作用后的拉伸性能

高温是高延性水泥基复合材料(ECC)在服役过程中可能面临的最不利工况之一,对比研究了聚乙烯醇纤维增强ECC(PVA-ECC)与钢纤维/聚乙烯醇纤维混杂增强ECC(HyECC)在常温以及200℃、400℃、600℃高温作用后的拉伸性能。研究发现,常温下利用钢纤维等量替代PVA纤维将劣化PVA-ECC的拉伸应变硬化能力。高温对PVA-ECC和HyECC的拉伸强度和拉伸韧性均有明显的劣化作用,高温作用后均已不具备拉伸应变硬化能力;PVA-ECC的拉伸强度与拉伸韧性随温度呈指数型衰减,钢纤维可以减缓HyECC拉伸强度与拉伸韧性的衰减速率;高温作用改变了PVA-ECC和HyECC的微观结构,PVA纤维在200℃时的软化以及400℃后的分解是2种ECC材料拉伸性能高温劣化的主要原因。

Tensile behavior of ECC after exposing to high temperature

High temperature is one of the worst conditions to engineered cementitious composite(ECC).In this paper,the tensile behaviors of PVA fiber reinforced ECC(PVA-ECC)and steel fiber+PVA fiber reinforced ECC(HyECC)at room temperature and after 200℃,400℃,600℃elevated temperature exposure were studied.The results indicate that equally replacing PVA fibers by steel fibers degraded the tensile hardening ability of PVA-ECC at room temperature.The elevated temperature posed a significant effect on the tensile strength and toughness of PVA-ECC and HyECC.Tensile strain hardening behavior of the two types of ECCs was eliminated after high temperature exposure.Tensile strength and toughness of PVA-ECC presented an exponential decay along with the increase of temperature.The addition of steel fiber slowed down the decay rate of tensile strength and toughness of HyECC.Elevated temperature changed the microstructures of PVA-ECC and HyECC.The softening at 200℃and decomposing at 400℃of PVA fiber was the main reasons for the tensile behavior degradation of the two kinds of ECCs.