New use of sugar cane straw ash in alkali-activated materials: A silica source for the preparation of the alkaline activator

Alkali silicates, expensive and highly pollutant chemical reagents, are required to produce the alkaline activator for high-performance alkali-activated materials. This study presents a new silica source for producing the alkaline activator, sugar cane straw ash (SCSA). An activating suspension was prepared with SCSA and NaOH by means of a thermal bottle. The ash reacting time inside the thermal bottle (τ) was assessed from 0 to 48 h, and the SCSA amount in suspension, represented by the SiO2/Na2O ratio (ε), was analysed from 0 to 1.82. Compressive strengths were obtained from blast-furnace slag-based mortars that were cured for three days at 65 °C, with the optimal mortars produced when τ = 24 h and ε = 1.46. Comparison of these new SCSA systems with two common silica sources, sodium silicate chemical reagent and rice husk ash, revealed that SCSA yielded lower results than the former and similar results to the latter silica source.