The synergistic mechanism of hydration regulation and carbonation curing on the carbon sequestration and impermeability enhancement of cementitious materials

Abstract

Carbonation curing, as a novel curing method, gradually plays an important role in the reduction of carbon emissions and the improvement of durability for cementitious materials. This study considers the intervention of carbonation at different ages of hydration and investigates the synergistic effect of nano-titanium dioxide (NT) regulating cement hydration and 20% CO2 carbonation curing on the enhancement of carbon sequestration and durability performance of cement mortar. The results show that early-age carbonation curing and the addition of NT increase the unit area carbon sequestration of cement mortar at the age of 28 days by 242.75% (0.41 kg/m2); meanwhile, some micro-nano-sized calcite crystals and NT jointly play a nucleation and filling role during hydration, optimizing the pore structure. As a result, the unit area capillary water absorption coefficient and gas permeability coefficient decrease by 70.55% and 91.89%, respectively, inhibiting the continuous diffusion of CO2 and achieving controlled surface carbonation. Based on the pore characteristics of the carbonated surface, this study also proposes a “Sieve filter” structure hypothesis model, which suggests a negative correlation between pore structure and surface depth under the synergistic mechanism. This can provide innovative ideas for the cement industry to enhance the durability performance of reinforced concrete prefabricated components using carbon sequestration technology.