Integrated Life Cycle Environmental Impact and Mechanical Durability-Related Assessment of Sustainable Pozzolanic Mortars

Abstract

The cement industry is a major contributor to global energy consumption and greenhouse gas emissions, motivating the development of sustainable cementitious materials through partial cement substitution. This study investigates the combined mechanical, durability-related, and environmental performance of mortars incorporating a 20% replacement of Portland cement by volume with different natural and waste-derived mineral additions, including natural pozzolan, brick waste, glass powder, recycled concrete powder, and calcined clay as pozzolanic or potentially reactive supplementary materials, while silica sand was used as an inert mineral filler. Mechanical performance was evaluated through compressive strength, while durability-related behavior was assessed using water absorption by immersion at 28 days. In parallel, a Life Cycle Assessment (LCA) was conducted to quantify the environmental impacts associated with climate change, acidification, eutrophication, photochemical oxidant formation, material resource depletion, and non-renewable energy consumption. The results show that mortars incorporating natural pozzolan and brick waste achieved compressive strengths comparable to the reference mortar, while maintaining low water absorption values, indicating effective microstructural densification. Glass powder also provided acceptable mechanical and durability-related performances, whereas silica sand, recycled concrete powder, and calcined clay exhibited reduced strength and increased absorption due to dilution effects, inherited porosity, or delayed pozzolanic activity. From an environmental perspective, all cement-substituted mortars demonstrated significant reductions across all assessed LCA impact categories, with decreases typically ranging from 15% to 20% relative to the reference mix. The most pronounced environmental benefits were observed for mortars incorporating waste-derived materials, particularly brick waste. Overall, the combined mechanical and environmental assessment demonstrates that a 20% cement substitution using supplementary materials can substantially reduce the environmental footprint of mortars without compromising essential engineering properties.