Investigation of the microstructure of Portland cement pastes with functionalized nanosilica with different contents of shrinkage-reducing additive

This research aims to verify the effect of NS functionalization with different mass ratios of shrinkage reducing additive (SRA) in cementitious composites. Four functionalized nanosilicas were produced, one with amine groups (NSFA) and three with different mass ratios of SRA/NSFA (5 %, 10 % and 15 %), named NSFArr. The properties of six different pastes were investigated, one produced only with Portland cement CP V-ARI and five replacing 1 % of Portland cement by NS and the mentioned functionalized nanosilicas. The compressive strength at 2, 7 and 28 days of hydration, the amount of CH and C-S-H through the XRD, TGA and FTIR techniques, as well as the porosity at 28 days of hydration through mercury intrusion porosimetry (MIP) were evaluated. The functionalization of NSFArr with different amounts of SRA caused a change in the hydration kinetics of the pastes, which impacted the mechanical performance and porous structure of the pastes. It was possible to observe an increase in the mechanical performance of the pastes with NSFArr at 28 days compared to the paste with NS, making this material promising for use in high-performance concretes.