A Novel Clinker-Free Binary Paste with Biomass Fly Ash and Slag

Biomass fly ash is one of the primary by-products in the biomass energy industry. Lack of proper management has resulted in the direct disposal and landfilling of biomass fly ash, resulting in secondary pollution. Owing to its high alkalinity and sulfate content, it is possible to use biomass fly ash as a solid activator to react with aluminosilicates-rich precursors. In this paper, we formulate a binary binder that contains 50% of biomass fly ash and 50% of slag by weight, without including cement clinker or chemical. The main hydration products of the binary binder are ettringite and C-A-S-H gels. The pastes exhibited a moderate compressive strength of 27.3 MPa with a water to binder ratio (W/B) of 0.4 at 28 days. The strength can be further improved to 45.8 MPa at 28 days, by reducing the w/s ratio to 0.25 with superplasticizers. The formulation of a clinker-free binder with a high proportion of biomass fly ash can be a sustainable strategy for biomass fly ash valorization.