A 100% waste-based alkali-activated material by using olive-stone biomass ash (OBA) and blast furnace slag (BFS)

This study presents the use of olive-stone biomass ash (OBA) as an alkali source in alkali-activated materials (AAM) based on blast furnace slag (BFS). The OBA was physically and chemically characterized. It presented high K2O and CaO contents, and yielded high alkalinity in water medium. The newly designed OBA + BFS mixes (a 100% waste-based AAM) reached a compressive strength of 30 MPa after 7 days of curing at 65 °C, which was higher than for BFS activated with KOH solution. Thermogravimetric studies showed the formation of C-S-H/(C,K)-A-S-H gels and hydrotalcite. The OBA presented excellent performance as a component in AAM and a good valorisation was achieved.