Control of carbonation mechanism in Portland Cement paste using synthetic carbon-capture aluminosilicates

In this research, synthetic aluminosilicate nanoparticles in the form of engineered synthetic aluminosilicates (ESA) were added to a cement paste to create a more controlled environment for carbonation and subsequent hydration reactions. To date, early-age CO2 curing of Portland cement pastes has been shown to reduce the later-age performance due to the decalcification of hydration products and starvation of water by early-age carbonation. However, in this study, it was demonstrated that it is possible to control the carbonation and subsequent hydration reactions through the addition of ESA. Two types of synthetic aluminosilicates were synthesised using organosilanes, tetraethoxysilane (TEOS), and functionalised organosilane, 3-aminopropyltriethoxysilane (APTES). The two aluminosilicates behaved slightly differently, confirming the possibility of altering the carbonation and subsequent hydration reactions. The research demonstrates that tailored nanoparticles enhance carbonate formation by preventing decalcification of the hydration product. The ESA took part in pozzolanic reactions which resulted in no starvation of water on carbonation and led to improved performance at a later age when compared to the samples without ESA. Furthermore, decalcification of portlandite was not observed on the addition of ESA. The carbonation reaction mechanisms on the addition of these ESAs were postulated, and the possibility of increase in carbon uptake without affecting the mechanical performance at later ages were shown.