Cracking behaviour and constitutive modelling of hybrid fibre reinforced concrete

Cracking is a multi-level process that damages the concrete structure or cement-based material. Nowadays, multi-scale hybrid fibres can be utilized in concrete to get more resistance against cracking. In this work, the reinforcing index and constitutive modelling are studied for plain concrete, single fibre reinforced concrete, two hybrid fibres reinforced concrete and multi-scale hybrid fibres reinforced concrete having different basalt fibre contents. The reinforcing index is calculated for hybrid fibres and empirical equations between strength properties and reinforcing index are developed. Also, the constitutive models of the compressive stress-strain relationship are well established and the comparison between experimental data and different models are made. Furthermore, energies absorbed and toughness indexes are obtained for compressive and flexural properties from the stress-strain and load-deflection curves, respectively. The SEM analysis is done to study the multi-level cracking mechanism and fibre-matrix bond. The results of empirical equation showed satisfactory results of strength properties with that of experimental results. The results obtained from different mathematical model of uniaxial compressive stress-strain curve are in good agreement with experimental data. It is revealed that the optimal mechanical properties for multi-scale hybrid fibre reinforced concrete was observed with 0.8% basalt fibre content, 1% CaCO3 whisker and 0.25% steel fibre content.