How environmentally sustainable are fibre reinforced alkali-activated concretes?

Abstract

Alkali-activated concretes have been receiving increasingly attention as they are identified to be key components towards achieving sustainable construction in future. A detailed comparative environmental assessment study of different mix-designs of fibre reinforced alkali-activated concretes (FRAAC), conventional concrete (CC) and steel fibre reinforced conventional concrete (SFRCC), was conducted using Life cycle assessment (LCA) methodology. LCA study was conducted to determine the environmental performance of the different FRAACs when compared to CC and SFRCC, and also to identify the most important contributing factors to their environmental burdens. Results from the contribution analysis conducted indicated that sodium silicate solution was the major contributing material in the different FRAACs mix-designs. This is because, in addition to the high amount of energy required in the production of sodium silicate solution, high quantities of the solution is required in the development of the alkali-activated concretes. Furthermore, sensitivity analysis conducted indicated that there is a high variability in the environmental assessment results when different life cycle inventory (LCI) data sources of sodium silicate solution are used. Thus, amount of constituents and source of LCI data used, can hugely influence the overall results of the LCA study. As a result, constituent materials required in the development of FRAACs (especially ones which result in higher environmental burdens in FRAACs e.g. sodium silicate) should be cautiously utilised. Alternatively, they can be substituted with materials of lower environmental impacts where applicable, while ensuring the mechanical properties of the alkali-activated concretes are not compromised upon.