Cracked permeability of hybrid-fibre-reinforced concrete Available to Purchase

The addition of fibre to concrete is a well-known technique for delaying the origination and propagation of micro-cracks in concrete upon loading. The permeation properties of concrete elements stressed either due to their own self-weight or upon loading cause micro-cracks to open up easily. This results in the easy intrusion of harmful chemical agents such as chlorides and sulfates and potentially disrupts the concrete integrity. The present study was aimed at adding two different fibre types (hybrid fibres) to concrete at different volume fraction (V_f) to improve the synergistic interaction of fibres at different cracking scales. The synergy of the hybrid fibres was evaluated in terms of the permeability resistance of different fibre concretes stressed at different load levels. The permeability test was carried out using the Germann water permeability method on concrete cubes subjected to uniaxial compressive stress wherein water is forced to enter under constant pressure. The coefficient of permeability (C_cp) of various hybrid fibre concretes containing metallic and non-metallic fibres was investigated systematically. The test results in this study showed that the coefficient of permeability decreased for all hybrid fibre concretes. However, the decrease was significant at higher non-metallic fibre (0·38% V_f) and lower steel fibre content (0·12% V_f). A good synergy of fibres was also observed for fibre combinations having shorter and low modulus fibres in comparison with the high modulus and longer length of steel fibres. Among all hybrid combinations, steel–glass fibre concrete showed a considerable reduction in coefficient of permeability of up to 62·47%, as the glass fibres were efficient in bridging the micro-cracks at low stress levels. The reduction in permeability of hybrid fibre concretes could be due to shorter lengths and large fibre availability at the crack front, which can significantly delay the crack nucleation and subsequent propagation.