Development of low-alkali, fly ash/slag geopolymers: Predictive strength modelling and analyses of impact of curing temperatures

Abstract

The present work analyses the effects of curing temperature (25, 40, 60◦C for 24 h), silicate modulus Ms value (1.5, 1.7, 2.0), and slag content (10, 20, 30, 40 wt%) on the compressive strength development (1, 7, 14, 28 days) of low-alkali geopolymer mortars with matrices from fly ash and blast furnace slag. These data were used to generate predictive models for 28-day compressive strength as a function of curing temperature and slag content. While the dominant variable for the 1-day compressive strength was the curing temperature, the slag content was dominant for the 28-day compressive strength. The ratio of the 1-day and 28-day compressive strengths as a function of curing temperature, Ms value, and slag content allows prediction of the maximal possible curing temperature and shows cold-weather casting to present an obstacle to setting. These data also allow prediction of the 28-day compressive strength using only the 1-day compressive strength.