The Impact Performance Experimental Study Of Steel And PVA Hybrid Fiber Reinforced Cementitious Composites

FRCCs (Fiber Reinforced Cementitious Composites) are the combination of hardened cement mortar as a matrix and discontinuous short-fiber or continuous long-fiber as a reinforcing material of a composite material. Current research in Fiber Reinforced Cementitious Composites is mainly concentrated on the mechanical properties under static loads, but research on its performance in high-speed dynamic loading is less, however, civil engineering structures in the earthquake, explosion, impact and other high-speed dynamic load often suffer devastating damage. So the dynamic mechanical properties of the structure materials gradually become the research hot spot in this area. View of this, the steel fiber of high elastic modulus and the PVA fiber of relatively low elastic modulus were chosen to mix together in this paper. Through adding single-doped or mixed fibers, fiber-reinforced cement-based composites of different sets mix were prepared, and flexural test, compression test, the four-point bending test, falling weight impact test and high-speed impact testing were used to study the mechanical properties of the above-mentioned fiber-reinforced cement-based composites. This research purposeis to achieve high strength and high ductility of structural materials.The first focus of this thesis is the quasi-static mechanical properties of the steel-PVA hybrid fiber reinforced cementitious composites ((Hybrid Fiber Reinforced Cementitious Composites) and the steel fiber reinforced cementitious composites(Steel Fiber Reinforced Cementitious Composites). The results of compression strength, flexural strength and four-point bending test showed that:in order to obtain the steady state cracks in the HFRCCs, the volumecontent of PVA should be higher than that of steel fiber, and the mix ratio with 1% Steel+1.5% PVA demonstrates better results; The increasing fiber content will improve the strength of steel fiber reinforced cementitious composites. But when the volume content of steel fiber is too high, the strength of SFRCCs exists an inflection point; The strength of SFRCCs is improved when water-cement ratio is lowered; If replacing some fly ash with large number of silica fume, the ductility of SFRCCs will improve further, but the overall flexural strength will declined.The second focus of this thesis is the low-speed or high-speed impact performance of PVA fibers, steel-PVA hybrid fiber and steel fiber. The drop hammer low-speed impact test results indicated that the flexural impact performance of steel-PVA hybrid fiber, in particular of the mix of 1.5% PVA+1% Steel is superior to the single-doped PVA fibers and steel fibers;The Hopkinsonv pressure Bar (SHPB) high-speed impact test results found that the impact performance of steel fiber reinforced cementitious composites is better than single-doped PVA fiber or hybrid fiber; When the steel fiber volume content is 4%, the highest index of toughness of SFRCCs will be obtained with the addition of silica fume.