Investigation of the Effect of Nano-Silica on the Compressive and Flexural Strength of Cement Mortar Reinforced with Polypropylene Fibers

Mortar is suitable for utilizing in compressed parts such as columns and arches due to its considerable compressive strength. However, despite this advantage, the relatively low tensile strength and brittleness of the mortar limit its use for components that are under tensile loads. Using fibers and nano-particles can be a way to reduce these problems. In this research work, various fiber reinforced and nano-engineered cement mortars have been successfully prepared through the addition of nanosilica into plain and fiber reinforced mortars. In this way, effects of nano-SiO2 on the mechanical properties of cement mortars with polypropylene fibers and also without it have been evaluated. Polypropylene fibers were used in lengths of 6-18 mm and aspect ratios of 300-900. The effect of fibers in two different percentages of 0.1% and 0.2%, and the influence of nano-silica in various percentages of 1, 2, 3, 4 and 5% on mortars with a water-to-binder weight ratio of 0.485 were evaluated and compared. A total of 108 cubic mortar samples with a dimension of 5×5×5 cm3 and 108 rectangular cubic samples with a dimension of 16×4×4 cm3 were made according to ASTM standards, and compressive and flexural strength tests were carried out on samples at the ages of 7 and 28 days. The results of the experiments indicated a significant enhancement in the mechanical properties of the prepared mortars, as the values of 7-day and 28-day compressive strength of the sample containing 0.1% fiber and 3% nano-SiO2 were increased by 51% and 61%, respectively, compared to the control sample. Besides, the values of 7-day and 28-day flexural strength of the sample containing 0.2% fiber and 3% nano-SiO2 were increased by 48% and 55%, respectively, compared to the control sample. A noticeable increase in mechanical properties indicated the suitable performance of this type of mortar.