Mechanical Properties of High-Strength Concrete Reinforced with Hybrid Basalt–Polypropylene Fibers under Dynamic Compression and Split Tension

Abstract

Fiber reinforcement has been widely used to improve the performance of concrete under different types of loading. Among various types of fibers, a combination of fiber types, namely hybrid fibers, has been shown to be more effective due to the combined features of different types of fibers. However, the dynamic performance of hybrid fiber-reinforced concrete (FRC) has been rarely studied. Recently, a new type of hybrid, consisting of 1% low Young’s modulus macro polypropylene (PP) fibers and 0.1% high Young’s modulus micro basalt fibers, has been proposed, showing improved static mechanical properties compared with traditional FRC. In this study, the dynamic compressive and splitting tensile properties of this new basalt-macro PP hybrid FRC with varying fiber volume dosages were investigated by using split the Hopkinson pressure bar (SHPB). Experimental results showed that the basalt–macro polypropylene hybrid FRC exhibits superior impact resistance compared with plain concrete under both dynamic compression and splitting tension. The hybrid FRC showed less crack initiation and propagation, a ductile failure pattern, and smaller crack opening displacement. The sensitivity of the concrete to strain rate was found to be more significant for 1% hybrid FRC under dynamic compression and 2% hybrid FRC under dynamic splitting tensile tests. Based on the test results, empirical formulas were derived to describe the dynamic increase factor (DIF) versus strain rate for both dynamic compressive and tensile strength of hybrid FRC.