Quantitative Assessment of Alkali-Activated Materials: Environmental Impact and Property Assessments

Abstract

This study compares greenhouse gas (GHG) emissions, embodied energy, and air pollutant emissions of alkali-activated mortars and conventional portland cement (PC)-based mortars. Alkali-activated materials (AAMs) do not require the use of PC to offer cementitious properties; these materials can valorize industrial waste streams and noncementitious natural resources. In this work, several AAMs containing blast-furnace slag and natural pozzolans were examined. Comparisons were drawn both based on the production on 1 m3 of material and based on ratios of GHG emissions to mortar strength. To facilitate robust assessments, mechanical and material properties were determined. GHG emissions, embodied energy, and nitrogen oxides (NOx), sulfur oxides (SOx), carbon monoxide (CO), and lead (Pb) emissions for the alkali-activated mortars were lower than their conventional counterparts. However, the AAMs exhibited higher volatile organic compound (VOC) and particulate matter 10 microns or smaller (PM10) emissions. When ratios of GHG emissions to strength were examined, results indicated that the lower environmental impacts of AAMs could be desirable relative to PC mortars, even when the AAMs displayed lower mechanical strength. These findings suggest that, depending on application, AAMs could contribute to environmental impact-mitigation strategies.