Influence of the cementitious matrix on the behavior of fiber reinforced concrete

Abstract One of the main purposes of the addition of fibers to the concrete is the control of the plastic shrinkage cracking in the fresh state and the increase of the post-crack resistance in the hardened state. The cementitious matrix is one of the factors that influences the performance of fiber reinforced concrete, interfering in the fluidity of the mixture and in the adhesion between fiber and matrix. In this context, the present paper evaluates the behavior of two concrete, one of conventional strength and another of high-strength, without fiber and with a content of 1%, by volume, of fiber, being used steel fiber and macro-polymeric fiber. For this, the mechanical properties of the concrete were evaluated in the hardened state by the tests of compressive strength, Barcelona, flexure of prisms and punching of plates. From the experimental results, statistically analyzed, there were significant changes in toughness and residual strength due to change in the cementitious matrix. Finally, an equivalence of performance between the fibers as to the toughness was observed, with the change of the cementitious matrix.摘要：在混凝土中掺入纤维的核心目的之一，是调控混凝土新拌状态下的塑性收缩开裂，并提升其硬化状态下的开裂后抗裂性能。胶凝基体（cementitious matrix）是影响纤维增强混凝土（fiber reinforced concrete）性能的关键因素之一，会对混合料的流动性以及纤维与基体间的界面粘结性能产生显著影响。在此研究背景下，本文针对两类混凝土展开性能评价：分别为常规强度混凝土与高强度混凝土，每组均设置未掺纤维、按体积掺量1%掺入钢纤维（steel fiber）以及按体积掺量1%掺入大尺寸聚合物纤维（macro-polymeric fiber）的试验工况。为此，本文通过抗压强度试验、巴塞罗那试验、棱柱体抗弯试验以及板件冲切试验，对混凝土硬化状态下的力学性能进行了测试与表征。对经统计分析的试验结果进行梳理后可见，胶凝基体的改变会对混凝土的韧性与残余强度产生显著影响。最终研究表明，随着胶凝基体的变化，两种纤维在韧性表现上呈现出等效性。