Effect of CO2 exposure on the mechanical strength of geopolymer-stabilized sandy soils

This is the final version. Available on open access from Elsevier via the DOI in this recordIn recent years, there has been growing interest in developing methods for mitigating greenhouse effect, as greenhouse gas emissions continue to contribute to global temperature rise. On the other hand, investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely conducted. However, the effect of CO2 exposure on the mechanical properties of geopolymer-stabilized soils is rarely reported. In this context, the effect of CO2 exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was investigated. Several factors were concerned, for example the binder content, relative density, CO2 pressure, curing condition, curing time, and carbonate content. The results showed that the compressive strength of the stabilized sandy soil specimens with 20% volcanic ash increased from 3 MPa to 11 MPa. It was also observed that 100 kPa CO2 pressure was the optimal pressure for strength development among the other pressures. The mechanical strength showed a direct relationship with binder content and carbonate content. Additionally, in the ambient curing (AC) condition, the mechanical strength and carbonate content increased with the curing time. However, the required water for carbonation evaporated after 7 d of oven curing (OC) condition and as a result, the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured samples. Moreover, the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate.MatSoil CompanyEuropean Union Horizon 202

Effect of CO2 exposure on the mechanical strength of geopolymer-stabilized sandy soils

In recent years, there has been growing interest in developing methods for mitigating greenhouse effect, as greenhouse gas emissions continue to contribute to global temperature rise. On the other hand, investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely conducted. However, the effect of CO2 exposure on the mechanical properties of geopolymer-stabilized soils is rarely reported. In this context, the effect of CO2 exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was investigated. Several factors were concerned, for example the binder content, relative density, CO2 pressure, curing condition, curing time, and carbonate content. The results showed that the compressive strength of the stabilized sandy soil specimens with 20% volcanic ash increased from 3 MPa to 11 MPa. It was also observed that 100 kPa CO2 pressure was the optimal pressure for strength development among the other pressures. The mechanical strength showed a direct relationship with binder content and carbonate content. Additionally, in the ambient curing (AC) condition, the mechanical strength and carbonate content increased with the curing time. However, the required water for carbonation evaporated after 7 d of oven curing (OC) condition and as a result, the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured samples. Moreover, the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate

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