Improvement of properties of architectural mortars prepared with 100% recycled glass by CO2 curing

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, CO2 curing was employed to ameliorate these drawbacks. The effect of CO2 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, CO2 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 CO2 gas to penetrate and diffuse more easily into the cementitious matrix, resulting in a higher degree of CO2 curing.