Development of durable class F fly ash based geopolymer concretes

Abstract

The production of Portland Cement (PC) has been shown to be responsible for 5-8% of global CO2 emissions. This has led to class F fly ash based geopolymer concrete being developed as a substiture for PC concrete for to reduce these global CO2 emissions. However, research has shown that each fly ash has unique characteristics and requires a specific mix design for each fly ash. This is can occupy a significant amount of time. Furthermore, before the mix can be adopted for commercial application it requires the long-term durability to be established. This gap is one of the primary limitations delaying the adoption of geopolymer concrete. While each fly ash is unique, they do have common characteristics which can be utilized to optimise the mix design process. Geopolymers are also known to have good durability characteristics, in particular for acid and sulphate exposure. This paper reports the mix design optimisation process for six class F fly ashes from Australia, Sri Lanka and Indonesia. The strength properties and durability performance of the optimised mixes is reported including the compressive strength development, chloride and carbonation resistance together with performance when exposed to sulphate and acidic media for the Indonesian fly ash, including to a simulated peat soil designed to replicate the conditions experienced in Indonesia.