Improvement of properties of architectural mortars prepared with 100% recycled glass by CO₂curing

Previous studies have well demonstrated that recycled glass (RG) can be incorporated into cementitious materials to replace 100% river sand as fine aggregates. However, this replacement was found to incur adverse effects on the mechanical properties of the cement mortar. In this study, CO ₂ curing was employed to ameliorate these drawbacks. The effect of CO ₂ curing on both of the mechanical properties and microstructure of the RG incorporated cement mortar was studied by a series of laboratory tests. The results showed that replacement of river sand by 100% RG led to a 37% decrease in compressive strength and a 32% reduction in flexural strength of the mortar samples under conventional curing. Whereas, CO ₂ curing of these samples significantly enhanced both the compressive and flexural strength, with a more pronounced improvement on the former. Such improvements were further reflected by a decrease in both the water absorption and porosity, and by an enhancement of the microstructure. This is attributed to the fact that compared with the mortar samples prepared with 100% river sand, those prepared with 100% RG had a more porous structure due to the smooth surface of RG and thus a poor bonding between the RG and the cement paste. However, such a porous structure encouraged CO ₂ gas to penetrate and diffuse more easily into the cementitious matrix, resulting in a higher degree of CO ₂ curing.