Alkali-activated mortars for sustainable construction material: effects of binder-to-aggregate ratio and curing conditions

Valorisation and reuse of industrial wastes has become a worldwide compelling topic to improve the sustainability of processes and materials. This paper discusses an alternative way to recycle the biomass fly ash, generated by the kraft pulp industry, to manufacture novel geopolymeric mortars intended for applications in construction. Biomass fly ash was used as a raw material, in partial substitution of the commonly used metakaolin, natural siliceous sand as aggregate. The followed manufacture process is highly simple and reproducible. Various proportions binder to aggregate were tested to study the effect on the final mortars properties. The mortars mechanical resistance was also studied in relation to the temperature and duration of curing in order to define the best condition to gain the maximum mechanical resistance. Also submersed curing was tested. Moreover, the mechanical performance was investigated under the effect of natural ageing. The investigations indicate that the novel mortars can be used as structural material in construction and represent an efficient solution to reduce the environmental footprint associated with waste disposal in light of the circular economy.