Performance enhancement of silica fume blended mortars using bio-functionalized nano-silica

Abstract

This work explores a naturally occurring bio-molecule, tannic acid (TA) to functionalize the colloidal nano-silica (NS) for better performance in the silica fume (SF) blended mortars. The functionalization process is achieved via mixing the colloidal NS with TA solution for 5 min. The introduction of well-dispersed nano-silica can improve the particle packing of silica fume blended mortars with better gradation. As a result, both mechanical properties and durability of produced mortars can be significantly enhanced. To this end, an experimental program was carried out to evaluate the effects of TA functionalization, including hydration kinetics, workability, setting time, compressive strength, pore structure, and nanomechanical properties. Testing results show that functionalizing with TA leads to up to 15% increase in the workability of silica fume blended mortars and more than 12% reduction of the porosity of pastes. These improvements are due to the filler effect of the nano-silica particles and higher packing density of hydration products induced by TA functionalization. As a result, the average elastic modulus and packing density of the major hydration product, calcium silicate hydrate (C-S-H) are increased by 8.15% and 2.68%, respectively, and the compressive strengths of the mortars at 28d is improved up to 34.97%.