Durability of high volume fly ash binders

Abstract

Fly ash (FA), a by-product from thermal power plants, has been used for decades as Portland cement replacement material. Recently, additional efforts have been made by scientist and engineers worldwide with an aim to increase, as much as possible, content of FA in a binder, thus reduce negative environmental and economic impacts of the power and cement production. Furthermore, extensive work is being done on evaluating properties of the new binders, with a goal to ensure their wider use. This work analyzes durability of the high volume FA binders (HVFA, ≥ 50 mass% of FA in a binder). In order to increase FA content and improve properties of the HVFA binders, FA was mechanically activated and a chemical activator was used for the binder synthesis. Freeze-thaw, carbonation and sulfate attack resistance of the binders were analyzed. It was found that the freeze-thaw resistance of the HVFA binder was in accordance with the standard requirements. Carbonation depth after 56 days of testing of the HVFA binder was 7.3–8.1 mm, and an increase in the compressive strength of the mortar was observed. Studying of the sulfate attack on the HVFA binder showed that the resistance of the FA based binder was good, and even superior to the performance of the Portland composite cement CEM II 42.5N, tested under the same conditions and used for comparison. The obtained results indicated that the HVFA binders can be used for applications where moderate compressive strength and good durability of the binder is needed.