Technoeconomic Study of Alkali-Activated Slag Concrete with a Focus on Strength, CO2 Emission, and Material Cost

Abstract

The present research evaluates the technoeconomic performance of alkali-activated slag (AAS) concrete in comparison with ordinary portland cement (OPC) concrete. Seventy-five AAS mixtures with a wide range of mixture proportions are produced, moist-cured, and tested for their workability (slump or slump flow) and compressive strength. The relative CO2 emission and material cost of the mixtures are also analyzed in comparison with OPC concrete. Regression analyses are carried out to model the mixtures’ consistency and compressive strength and relate them to the governing factors [i.e., (Na+K)/Si, Ca/Si, and (H2O/Solids)vol.]. The extent of the effects and the interactions of such factors on the strength and slump of AAS concrete is quantitatively determined. A multiresponse optimization method with the aim of maximizing the strength for a targeted slump range while minimizing the relative cost and CO2 emission is introduced, and the mixture proportions yielding such conditions are identified. The results suggest that at molar ratios (Na+K)/Si=0.55, Ca/Si=1.01, and volume ratio (H2O/Solids)vol.=1.0, workable AAS mixtures (slump=90 mm) could be produced with strength values exceeding twice the amount and CO2 emissions half that of OPC concrete while maintaining the material cost increase below 40%.