Early properties of concrete with alkali-activated fly ash as partial cement replacement

Cement manufacture is one of the reasons for society's increasing carbon dioxide footprint. The development of a sustainable construction material is therefore needed to replace Portland cement fully or partially in building construction applications. Geopolymer concrete is a sustainable cementitious material, which is claimed to reduce carbon dioxide emissions and utilise waste materials such as fly ash, metakaolin and blast-furnace slag. Fly-ash-based geopolymer concrete with an activating solution of a mixture of silica fume, sodium hydroxide and water was investigated. Four Portland cement replacement weight ratios (0%, 5%, 10% and 15% by weight of fly ash) were studied. The effects of the Portland cement replacement on the early geopolymerisation process, compressive strength, modulus of elasticity and Poisson's ratio were investigated. Acoustic emission monitoring results showed that the early geopolymerisation process was enhanced when Portland cement replacement was increased. The compressive strength and modulus of elasticity were significantly increased when the Portland cement ratio increased, while Poisson's ratio was adversely affected.