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.
Highlights
Geopolymers are novel low CO2 substitutes for ordinary Portland cement (OPC) [1]and are fabricated by reacting aluminosilicate- and/or silica-containing sources such as low-CaO Class F fly ash (FA), metakaolin (MK), and ground granulated blast furnace slag (GGBFS) with an alkaline activator solution
An increase in curing temperature resulted in the acceleration of the polymerisation reaction during curing for 24 h, there was a decrease in the rate of strength development with increasing temperature for all Ms values
A minimum of 20 wt% slag is necessary for the fabrication of low-alkali heat-cured geopolymers
Summary
Geopolymers are novel low CO2 substitutes for ordinary Portland cement (OPC) [1]. and are fabricated by reacting aluminosilicate- and/or silica-containing sources such as low-CaO Class F fly ash (FA), metakaolin (MK), and ground granulated blast furnace slag (GGBFS) with an alkaline activator solution. One of the most informative studies is by Rovnaník [15], who investigated the effect of curing temperature on the setting behaviour and compressive strengths of metakaolinbased geopolymer mortars These data, which are shown, reveal the following trends:. In a second comprehensive study, Chindaprasirt et al [16] investigated the compressive strengths of geopolymer mortars based on high-CaO Class C fly ash that were cured for 48 h at different temperatures, followed by ambient ageing to 90 days. There has not been any systematic investigation of the simultaneous effects of curing temperatures (25, 40, 60 ◦C for 24 h), silicate modulus Ms values (1.5, 1.7, 2.0), and fly ash/slag ratios (90/10, 80/20, 70/30, 60/40 wt%) on the compressive strength development (1, 7, 14, 28 days) for geopolymer mortars.
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