Analysis of Direct Functionalization of Nanosilica with APTES for Application in Cementitious Composites

Abstract

Functionalized nanosilica is the product resulting from the surface treatment of nanosilica (NS) through the coupling of various functional groups on its surface, in order to reduce the negative effects related to its dispersion and high reactivity. The application of NSF in cementitious pastes can promote the development of a denser matrix, increasing the gain in strength and durability. This article has the objective of discussing the effects of direct functionalization of NS) with aminosilane from a colloidal NS and reagent 3 -aminopropyltriethoxysilane (APTES), without using any chemical solvent. A first reaction was prepared with the reagents 4 mL of APTES, 100 mL of dichloromethane (H2CCl2) and 60 mL, forming NSF4. An alternative reaction process was developed, removing dichloromethane and without using any other solvent, forming NSF4WD. Some techniques were used to evaluate the efficiency of the reactions: pH, solids content, DLS, Zeta potential, XRD, TGA and FTIR. Portland cement pastes and mortars were produced to evaluate the effect of NS produced by the two different functionalization processes on hydration kinetics, porosity and compressive strength (at 1, 3, 7 and 28 days). The results showed that the use of dichloromethane in the functionalization process does not present significant contributions, since NSF4WD presented similar results to NSF4. It is concluded that the direct alternative method proved to be effective in grafting APTES onto the NS surface, in addition to meet the principles of Green Chemistry by not using toxic solvents, minimizing negative impacts on the environment and optimizing the functionalization process.