Triaxial mechanical behaviour of hybrid basalt–polypropylene fibre-reinforced concrete: The effect of micro-fibres at multi scale levels

The triaxial mechanical properties of hybrid basalt–polypropylene fibre-reinforced concrete (HBPRC) were investigated in detail. The different effects of micro-basalt fibre (BF) and micro-polypropylene fibre (PF) on the triaxial properties of concrete were revealed. The strength criterion for HBPRC was established. The results showed that the hydrostatic behaviour, volumetric strain, peak deviatoric stress, elastic modulus, and Poisson’s ratio of HBPRC are affected by not only the confining pressure but also the BF and PF. The confining pressure gradually changes the failure mode of HBPRC from split failure to shear failure and extrusion plastic flow failure. The BF and PF mainly improve the strength and deformation performance of concrete, respectively. A nonlinear Mohr–Coulomb (M–C) strength criterion for HBPRC, which takes into account the fibre effect, is established. The calculated results performed using the proposed criterion agree well with the experimental results.