CO₂ avoidance cost of fly ash geopolymer concrete

Using geopolymer concrete (GC) is a technically feasible decarbonization strategy in the cement and concrete industry shown by numerous papers. A key factor determining its commercial application is whether its cost is competitive. However, related study is scarce. In this paper, we present the analysis of GC's CO2 avoidance cost, the cost incurred to reduce one metric ton of CO2 emissions. The results show that among the 486 GC mixtures analyzed, only seven yield negative CO2 avoidance costs, while 379 are even more expensive than capturing CO2 from cement plants, which is another technically feasible decarbonization strategy and has been evaluated to have a CO2 avoidance cost of 55 USD/tCO(2) in Chinese demonstration project. Only a few GC mixtures with lower CO2 avoidance costs will be considered by the industry, and they are associated with low activator dosage and high compressive strength. To quantify this relationship, we introduce the activator index (Ai), which refers to the activator dosage (kg center dot m(-3)) required to achieve 1 MPa of compressive strength. The result shows that Ai values below certain thresholds correspond to lower CO2 avoidance costs and significant emission reductions of GC. This Ai-based criterion helps identify the optimal GC mixture that effectively reduces CO2 emissions at the lowest possible cost, thereby promoting its commercial application.