Alkali-activated cements utilising fly ash can be a low-carbon alternative to Portland cement. However, fly ash alkaliactivated
cements require curing at elevated temperature and have cost plus environmental implications owing to the
use of strong alkali solutions. Unclassified fly ash, silica fume, calcium hydroxide and sodium carbonate were used to
develop novel one-part fly ash alkali-activated cements. When cured at ambient conditions, the cements gained
compressive strength up to 11.0 and 44.2 MPa at 3 and 28 days, respectively. Microstructural investigations revealed
that cation exchange reaction between the activators was the key element in the development of the microstructure
and strength of the cements. The novel fly ash alkali-activated cements have at least 50% lower impact on global
warming than highly blended Portland cements.