Abstract:Fibre reinforced concrete possesses more excellent properties of cracking resistance, reinforcing strength and toughness than plain concrete, hence can fulfill more requirements in the modern concrete constructions. In the current paper, the twisted ultra-high molecular weight polyethylene (UHMWPE) fibre of high strength, high elastic modulus as well as low density was employed as the reinforcement, the quasi-static mechanical properties of a new type of fibre concrete (FRC) were experimentally investigated. The C70 high strength concretes with four different fiber volume fractions (FVF) were developed by improving the process of preparation, then the splitting tensile tests, cubic uniaxial compression tests as well as the prism axial compression tests of the FRC were conducted, respectively, to investigate the effect of the FVF on quasi-static strengths and deformation behaviors of the FRC. The comparisons between the mechanical properties of current studied UHMWPE FRC and concrete reinforced by general UHMWPE fibre without treatment as well as the Polypropylene fibre have been performed. The results show that the fibre dispersed more evenly using this improved mixing method which promoted the workability of FRC. The integrity of concrete was maintained and fall-out of fragments was avoided due to the added UHMWPE fibre. The splitting tensile strength, increasing from 47.2% to 78.6% with the fiber content from 0.3% to 1.0% compared with the plain concrete, was significantly improved by the twisted UHMWPE fibre. However, the compressive strength of the concrete was not significantly enhanced by the UHMWPE fibre, while the improvement of the residual compressive strength was remarkable. Both the peak compressive strain and Poisson’s ratio increased with the increase of the FVF, whereas the elastic modulus had an opposite variation trend. The compressive toughness index ηc15.5 of FRC was 1.40~2.53 times of that of the plain concrete. Twisted UHMWPE fibre has improved the splitting tensile strength of concrete more significantly than the other two types of fibres, and enhanced the uniaxial compressive strength to a certain degree.