Agro-Waste Ash as an Alkaline Activator for Zero-Portland Cement Mortars

Alkali-activated binders (AAB) are known for their reduced global warming potential compared to traditional portland cement-based binders. However, their adoption has been hindered by practical challenges such as high cost and causticity of activators, which limits their use in the field. This study explores an approach using biomass ash derived from agricultural waste, such as almond shells and hulls, as an activator to replace chemicals. Preliminary results indicate that AAB mortars activated with almond shells reach compressive strength comparable to carbonate-activated control and 30-40% higher than hydroxide-activated mortar. Paver blocks and concrete were prepared with compressive cylinder strengths over 30 MPa. Challenges with these materials largely revolve around reducing dry shrinkage, setting time. The findings can be extended to other agro-waste products with high potassium or sodium content in their ashes, diverting more ashes from landfills and promoting a circular economy.