Development of Eco-Efficient Fly Ash–Based Alkali-Activated and Geopolymer Composites with Reduced Alkaline Activator Dosage

Abstract

The eco-efficiency and economy of geopolymer composites largely depend on their alkaline activator dosage. In this study, the effect of applying a pre-setting pressure and variation of the aggregate-to-fly ash ratio on the alkaline solution dosage and mechanical strength of fly ash–based geopolymer composites was explored. It is shown that through control of the aggregate-to-ash ratio and application of pre-setting pressure, compressive strength could be increased by 102% and 86% for Class F fly ash–based geopolymer and alkali-activated Class C fly ash–based mixture, respectively. The total alkaline solution consumption could be reduced from 718 to 188 kg/m3 and from 769 to 262 kg/m3 for Class F fly ash–based geopolymer and alkali-activated Class C fly ash–based mixture, respectively. The proposed method reduced the alkaline solution consumption per compressive strength (6.2 kg·m−3·MPa−1) by up to 85% compared to that of the reference manually consolidated control geopolymer. The findings demonstrate that fly ash–based geopolymers could be made more sustainable and eco-efficient through tailored production techniques.