Alkali-Activated Paste Based on Biomass Ash

The increasing demand for sustainable alternatives in civil construction has spurred the development of cementitious materials with reduced environmental impact. In this context, alkali-activated materials have emerged as a promising solution, enabling the partial replacement of Portland cement with industrial by-products, such as biomass ash and fly ash. This paper investigates the use of biomass ash from the ceramic industry (CBA) and the cellulose industry (PBA), in binary mixtures with fly ash (FA), in the production of alkaline-activated cementitious pastes. Mini-slump, setting time, compressive strength, water absorption and scanning electron microscopy (SEM) tests were performed. CBA with a high calcium content (86.23%), showed greater reactivity and better mechanical performance in the pastes. In contrast, PBA, characterized by a high silica content (65.9%) and a low calcium content (6.54%), exhibiting higher compressive strength (30,66 MPa), but lower workability indices. The results demonstrate that these ashes are viable alternatives to Portland cement, contributing to sustainability and the circular economy by reusing industrial waste. However, the variability in ash properties requires strict control to ensure consistency and optimization of composites.