Effects of fibre hybridization on multiple cracking potential of cement-based composites under flexural loading

The effects of individual and combined additions of polypropylene (PP) and polyvinyl-alcohol (PVA) fibres (PP/PVA fibre ratios: 3/0%, 2/1%, 1.5/1.5%, 1/2% and 0/3%) on the flexural behaviour of cement-based composites have been investigated. For this purpose, matrices at different strength grades have been used. The binder composition of high strength matrix (MI) was solely cement and 50% of cement was replaced with fly ash to prepare a comparatively low strength matrix (MII). Thirty prismatic samples are subjected to four-point flexural loading after 28 days of standard curing. The load–mid-span deflection curves have been plotted and simultaneously cracking patterns of composites have been photographed at definite deflection values. First cracking and flexural strength, deflection and relative toughness values have been determined for all samples.Test results showed that the effects of PP and PVA fibres on load–deflection curves of cement-based composites are significantly different. Matrix strength is found as the dominant factor determining the flexural performance of fibre reinforced composites. Hybrid usage of PP and PVA fibres caused no significant improvement on flexural strength, relative toughness values and multiple cracking performances of composites.

► PP and PVA fibres affected the load–deflection curves in different manners.
► Increase in PP/PVA fibre ratio improved the ductility of composites.
► Hybrid fibre usage caused no synergistic flexural strength improvement.
► Matrix strength is the dominant factor determining flexural performance.