Investigating accelerated carbonation for alkali activated slag stabilized sandy soil

Portland cement as a commonly used material in soil stabilization projects, releases considerable amounts of CO2 into the atmosphere, highlighting the need to use green binders such as ground granulated blast furnace slag as a substitute for cement. On the other side, extensive research is being conducted on accelerated carbonation treatment to decrease the industry’s carbon footprint. Carbonation transforms CO2 into carbonate minerals. This study investigates the influence of accelerated carbonation on the unconfined compressive strength (UCS) of soil stabilized with alkali-activated slag under ambient and oven curing conditions. Effects of curing time, binder content, relative density, and carbonation pressure (100, 200, and 300 kPa) were also studied. Furthermore, a calcimeter test was conducted to determine the amount of carbonate generated, which reflects CO2 sequestration in soil. The results showed that the carbonated samples achieved higher strength than the non-carbonated samples. However, a slight decrease in UCS was observed with the increase in CO2 pressure. The generated carbonate content directly correlated with the UCS of the samples, which explained the higher strength of carbonated samples. Also, the ambient curing condition was more favorable for the samples stabilized with GGBS, which can be attributed to the supply of required moisture. Results from XRD, SEM, and FTIR indicated that the strength development was due mainly to the formation of carbonation products (CaCO3), which facilitated the densification of solidified materials.