Experimental Investigation on the Mix Proportion of Fiber-Reinforced Ultrahigh-Strength Grouting Material

Abstract

Concrete tends to develop cracks once damaged, and wide cracks specifically would affect the whole structure negatively. When used for repairing wide cracks, traditional cement-based grouting materials could no longer meet the demand for tensile strength. The paper aims to develop a high-performance grouting material for crack repair and further investigate its fluidity, and compressive strength, flexural strength, and splitting tensile strength after hardening. Based on the design of ultrahigh-performance concrete (UHPC), this grouting material consists of cement, sand, water, superplasticizer, expansion agent, silica fume, fly ash, and flat copper-plated steel fiber. The initial fluidity and 30-min fluidity of the grouting material decreased with the addition of fly ash, silica fume, and flat copper-plated steel fiber, among which the silica fume had the greatest influence on the fluidity, followed by fly ash and steel fiber. The optimal content of flat copper-plated steel fiber, fly ash, and silica fume was 2%, 10%, and 15%, respectively. Furthermore, the prediction model of compressive strength of grouting material was established. It indicated that cement grade, water-cement ratio, curing age, silica fume, fly ash, and flat copper-plated steel fiber and can be used for the mix proportion design of grouting materials.