Effect of Colloidal Nano-Silica on the Mechanical and Durability Performances of Mortar

Abstract

s. The mechanical and durability properties of cement mortars with colloidal nanosilica (CNS) were investigated experimentally. Reference mortar with a low water-to-cement ratio of 0.30 was used in this study. The influence of CNS was evaluated by adding 0.5, 1.0, 1.5 and 2.0% of CNS by weight of cement. CNS was first stirred in the mixing water for 2 minutes before added to cement and sand. Superplasticizer was used to maintain the same flowability. Results showed that the compressive strength consistently increases with higher dosage of CNS at all the curing ages, due to both hydration acceleration and pozzolanic reaction. With the increase in CNS, the migration coefficient and water sorptivity consistently decreased; with 2% of CNS, the migration coefficient and water sorptivity were reduced by 45% and 30% respectively in comparison with the reference mortar. The improved durability could be explained by the reduction and refinement in the porosity, which can be attributed to nanofiller effect and pozzolanic reaction of nanosilica. Furthermore, the addition of CNS could reduce the drying shrinkage by densifying the microstructure in the cement paste, which has not been reported previously.