Constitutive behaviour and modelling of hybrid basalt–polypropylene fibre-reinforced concrete considering coupling effect of fibre reinforcement and mechanical damage

The uniaxial compressive stress–strain behaviour of hybrid basalt–polypropylene fibre-reinforced concrete (HBPRC) having different matrix strengths was investigated. The results showed that basalt fibre (BF) and polypropylene fibre (PF) reduce the damage degree of concrete and gradually change the concrete failure mode from shear failure to longitudinal splitting failure. BF and PF improve the critical strain and peak stress of concrete, and the improvement effect of BF is greater than that of PF. However, addition of an excessive amount of hybrid fibre reduces the peak stress of concrete. BF addition increases the elastic modulus of concrete, whereas PF addition decreases it. Addition of an appropriate amount of hybrid fibre has a positive effect on the elastic modulus of concrete. The toughness of concrete increases with the addition of BF and PF and the increase in the matrix strength. When HBPRC is destroyed, BF mainly shows tensile failure, whereas PF mainly shows pull-out failure and undergoes extrusion and torsion deformation. BF and PF mainly improve the strength and deformation performance of concrete, respectively. A constitutive model for HBPRC that considers the effects of both mechanical damage and fibre reinforcement is established.