Fly ash based alkali-activated materials cured under ambient conditions

Abstract

The disposal of fly ash into landfills is quickly becoming a cause of environmental concern. At the same time the construction industry urgently needs sustainable materials with reduced environmental impact. Alkali-activated materials can utilise fly ash as a source material to produce low carbon cements that can perform on par with Portland cement. However, fly ash alkali-activated materials require elevated temperature curing and has cost plus environmental implications due to the use of strong alkaline solutions. The aim of this study was to develop novel one-part fly ash alkali-activated cements for ambient applications. Unclassified fly ash was blended with silica fume and low environmental impact cost-effective activators, calcium hydroxide and sodium carbonate, to produce the novel cements. Cured at ambient conditions, the developed novel one-part fly ash alkali-activated cements gained compressive strength up to 11.0 and 44.2 MPa at 3 and 28 days respectively. Statistical analysis and microstructural investigations revealed that sodium carbonate and calcium hydroxide concentrations were the main factors that positively affected the strength development. The cation exchange reaction between calcium hydroxide and sodium carbonate was the key element in microstructural development of the cements