Mix design optimization and environmental impact assessment of low-carbon materials containing alkali-activated slag and high CaO fly ash

This study aimed to analyze the sustainability and engineering properties of low-carbon materials (LCMs) using alkali-activated slag (AAS) and high CaO fly ash (HCFA), and to derive their expected effects on the optimal binder weight range. Towards this end, experiments were conducted by setting the W/B ratio of liquid B to three different levels (100, 120, and 140%) and the replacement ratio at 50, 60, and 70%. The results showed that as the binder weight increases, the geltime of ordinary Portland cement (OPC) and LCMs decreases, but the homogel strength tends to increase. In addition, it was found that as the binder weight increases by 100 kg/m³, the global warming potential (GWP) of OPC and LCMs shows a tendency to increase by 53.3 and 25.4 kg CO₂ eq/m³, respectively. The optimal binder weight ranges of OPC and LCMs that satisfy both the target geltime (20–50 s) and the target homogel strength (2 MPa or higher, at 7 days) were found to be 227.7–470.4 and 182.9–432.3 kg/m³, respectively. The analysis also revealed that the GWP for each were 127.7–256.9 and 52.8–116.0 kg CO₂ eq/m³, respectively. Therefore, it is expected that when the optimal binder weight range is applied to replace OPC with an LCM in the actual field, the GWP will be reduced by 74.9–140.9 kg CO₂ eq/m³.