Reactivity and Performance of Alkali-Activated Yallourn Brown Coal Ash

An investigation has been conducted to identify the reaction mechanism and compressive strength of geopolymer made from brown coal fly ash from two locations at Yallourn power station in Australia. The Yallourn–1 (Y1) ash has completed the storage period within the pond, whereas Yallourn–2 (Y2) ash has been stored in the pond for a short period of time. Compressive strength of Y1 geopolymer increased from 12.63 MPa (1.83 ksi) at 7 days to 13.62 MPa (1.98 ksi) at 28 days and 15.90 MPa (2.31 ksi) by 90 days, whereas Y2 achieved 13.26 MPa (1.92 ksi) at 7 days but reduced in strength to 8.55 MPa (1.24 ksi) by 28 days, followed by an increase in strength to 14.00 MPa (2.03 ksi) by 90 days. The low strengths observed is attributed to the low of alumina content of the Yallourn ash, coupled with the higher unburnt carbon content.