Effects of randomly distributed discrete short PVA fibers on impact strength of cement based composite

The aim of this research is to investigate the performance of randomly distributed polyvinyl alcohol (PVA) fibers of 6 mm length in cementitious composite. Based on total weight, three fiber contents (0.5%, 1% and 1.5%) by weight of cement were evaluated for their effect on static and dynamic mechanical properties of hardened mixtures. Providing a basis for comparison, control specimens were cast without fly ash. For all mixtures, water to cement ratio kept constant (0.45) and the maximum aggregate size was taken 4.75 mm. Poly carboxylate super plasticizer also used,1.5% by weight of cement to keep flow ability of the mix. All casted experiments demolded after 24 hours and cured in saturated lime water for 28 days and tested at the day of 35. By carrying out basic mechanical tests, it was observed that presence of PVA fibers slightly decrease the compressive strength but increase the flexural strength of cementitious composite. Major influence was observed in tensile and impact behavior. The absorbed impact energy provided by the mechanisms of matrix cracking, PVA fiber/matrix interface debonding and fiber rupture. The SEM analysis showed that the introduced PVA fiber acted as bridge across the crack, which improved the load-transfer efficiency and reduce the spalling of fragments. The experimental result showed that the addition of PVA fibers at 1.5% by weight of cement is the optimal improvement in the flexural, tensile and impact resistance of experiments.