Alternative binder systems: Cumulative assessment of environmental and functional parameters

Abstract

The construction industry's impact on environmental policy represents a major challenge for upcoming decades with a particular focus on the reduction of Portland cement use. The use of alkali-activated materials (AAMs) is being accepted as a viable pathway for a sustainable future of the construction industry thanks to the utilization of various waste materials. This study critically compares the functional and environmental performance of alternative AAMs with an emphasis on different processing requirements. Specifically, the effects of ready-to-use precursors (waste brick powder-WBP, granulated blast furnace slag-GBFS, clay freshwater sediments (CFS) requiring calcination, energy-intensive alkaline activators, and biomass fly ash as a partial cement replacement are studied by Life cycle assessment analysis. The analysis reveals the differences in the form of saved emissions for all analyzed strength classes (20 MPa, 30 MPa, and 40 MPa). The cumulative environmental score is reduced by 26 % in the 20 MPa strength grade, and by 29 % for the 30 MPa and 40 MPa grades in comparison with AAMs based on CFS precursors and blended cement with BFA. The results indicate that AAMs cannot be deemed a universal solution in terms of reduced environmental impact, due to the use of alkaline activators. Based on sensitivity analysis, AAMs may provide a more favorable material than Portland cement or even blended cement, but when using precursors that are difficult to process and inappropriate mix design, they can pose a higher burden than conventional cement-based binders.