Effect of coffee husk ash as alkaline activator in one-part alkali-activated binder

Coffee husk ash (CHA) was utilized as the alkaline activator with blast-furnace slag (BFS) as the solid precursor to produce a one-part alkali-activated binder (OP-AAB). CHA was prepared in the laboratory to achieve the best alkaline activator properties. The ash was physicochemically characterized. Physical/mechanical properties of mortars and microstructural analysis of pastes were performed to evaluate CHA influence in OP-AAB. Results showed that CHA presented high K2O content (as potassium carbonate), adequate solubility, and pH. Mortars' compressive strength revealed that CHA-based samples achieved over 40 MPa after 28 days. Microstructural studies showed that CHA completely reacted with BFS and generated a dense structure of (K,C)-A-S-H reaction product.