混杂纤维增强高性能混凝土弯曲韧性研究

Flexural toughness of high-performance hybrid fiber reinforced concrete

选用钢纤维、塑钢纤维和杜拉纤维,在总体积掺率不超过1%条件下,进行了二元或三元混杂纤维增强高性能混凝土的抗压试验、劈拉试验以及带切口梁三点弯曲试验.绘制了荷载-挠度曲线以及荷载-裂缝开口位移曲线(CMOD),计算得到了混凝土开裂各阶段纤维所贡献的能量吸收值以及等效弯拉强度,对比分析了纤维混杂方式、掺量对混凝土基本力学性能以及峰值荷载后变形性能的影响.研究结果表明:三元混杂纤维混凝土具有较基体混凝土、单掺或二元混杂纤维增强混凝土更优的力学性能和变形性能,弯拉强度最大提高了28%,弯曲韧性试验荷载-位移曲线均呈现出明显的应变硬化现象,并表现出优越的裂缝控制能力;当纤维三元混杂且水灰比为0.31时,由0.7%弓形钢纤维、0.19%塑钢纤维与0.11%杜拉纤维混杂制得混凝土样本的强度以及弯曲韧性最优.

The primary objective of this paper is to focus on the flexural toughness of the hybrid fiber reinforced concrete. The steel fiber, modified polypropylene fiber and polypropylene fiber chosen as three elements were used to be reinforcement in concrete with total volume fraction of fibers not more than 1%. The compressive test, splitting tensile one and the flexural toughness one were made on eight groups of specimens. Based on the stress-deflection and stress-CMOD （crack mouth opening dis- placement） curves, the equivalent flexural tensile strength and the energy absorption value of fibers, the effect of fiber volume fraction and hybrid mode upon concreteI mechanical properties and post-peak behavior were investigated. The results show that compared with hybrid fiber reinforced concrete and the plain concrete, the three different type of fiber in a suitable combination can significantly improve the mechanical properties and the post-peak behavior of concrete; the equivalent flexural tensile strength is increase largely by 28% ; all groups of the specimens show the phenomena of strain harden- ing and a better crack control ability of the concrete; the specimen with 0.7% of steel fiber, 0.19% modified polypropylene fiber and 0. 11%polypropylene fiber show the better flexural toughness and the higher strength at the ration water to concrete of 0.31.