Experimental study of mechanical properties of double-helix BFRP fiber reinforced concrete at high strain rates

Abstract

Fibers made of basalt fiber reinforced polymer (BFRP) have been used to reinforce concrete material. BFRP fiber with double-helix geometry was recently proposed, with demonstrated superior bond-slip behavior between fiber and concrete matrix hence improved reinforcing effects on concrete materials. To further examine the contribution of double-helix BFRP fibers to the impact resistance of concrete material, this study carries out laboratory tests to investigate the static and dynamic properties of BFRP fiber reinforced concrete (BFRC) under compression and tension loadings. The investigation on the influence of volume fraction of double-helix BFRP fibers on the mechanical properties of concrete under quasi-static loads is firstly presented. It is found that increasing BFRP fiber volume fraction up to 1.5% leads to improved compressive strength, splitting tensile strength and flexural performance of BFRC. The toughness of BFRC with 1.5% fiber volume fraction is 3.8 times that of plain concrete at the deflection of 3 mm and the uniaxial compressive strength and splitting tensile strength are increased by 10.7% and 16.2%, respectively. Furthermore, the dynamic mechanical properties of BFRC with 1.5% fiber volume fraction were investigated by compressive, spitting tensile and spall tests using split Hopkinson pressure bar test systems. Test results reveal that the addition of double-helix BFRP fibers enhances the strain rate sensitivity of concrete in terms of strength, ductility and energy absorption capacities, and the rate sensitivity is more significant with the increase of strain rate. Based on the test results, empirical formulas of DIF-strain rate relations for compressive and tensile strengths of BFRC are proposed.