Mechanical properties of steel microfiber reinforced cement pastes and mortars

An experimental study was carried out to assess the mechanical properties of high-performance pastes and mortars reinforced with steel microfibers. Two series of mixtures were made with three microfiber contents (0, 2.5, and 5% of the paste volume), three sand-to-binder ratios (S/B = 0, 1, and 2); and three sand gradings. In the first series, 21 mixtures were batched under vacuum to avoid air entrainment. In the second series, 10 additional mixtures were batched with and without a defoaming admixture. After 14 days of curing, compressive tests and third-point loading flexural tests were carried out on paste and mortar specimens. Tensile tests were also carried out after a 3-month curing period. The results obtained indicate that the batching of mixtures under vacuum and the use of a defoaming admixture were found to be two efficient ways to significantly lower the air content in microfiber reinforced mortars. They also reveal that the addition of microfibers significantly improves the mechanical properties of the cement pastes but provides only little improvement for the mortars.