Sensitivity of the Flexural Performance of Glass and Synthetic FRC to Fibre Dosage and Water/Cement Ratio

A comparative analysis of the flexural performance of FRC mixes with either glass or synthetic fibers is presented in this paper. The data used for such analysis were obtained from an experimental programme which comprised 42 notched prismatic specimens, produced and tested to EN 14651 at the age of 28 days. Different fibre dosages up to 15 kg/m3 were considered in two series of mixes with water/cement ratios of 0.26 and 0.39, which yielded average compressive strength values of 65 MPa and 50 MPa respectively. A direct correlation between fibre content and residual flexural strength was confirmed. However, statistically significant differences were observed between the two fibre types considered. FRC mixes with glass fibre contents up to 5 kg/m3 failed immediately after the first crack and showed no residual flexural strength. In general, specimens reinforced with synthetic fibres showed better levels of residual flexural strength and toughness than their glass fibre counterparts. The ratio between the residual flexural strength and the limit of proportionality provides a good illustration of such observations: it was 61% on average for FRC mixes with synthetic fibers at 10 kg/m3, whilst it was only 33% for FRC mixes with the same amount of glass fibers.