Effect of curing temperature on the development of hard structure of metakaolin-based geopolymer

The properties of metakaolin-based geopolymer are directly impacted not only by the specific surface and composition of initial metakaolin and the type, composition and relative amount of alkali activator used but they also depend on the conditions during the initial period of geopolymerization reaction. This study aimed to analyze the effect of curing temperature (10, 20, 40, 60 and 80 °C) and time on the compressive and flexural strengths, pore distribution and microstructure of alkali activated metakaolin material. The results have shown that the treatment of fresh mixture at elevated temperatures accelerates the strengths development but the 28 days mechanical properties are deteriorated in comparison with results obtained for mixtures that were treated at an ambient or slightly decreased temperature. The influence of curing temperature on microstructure of geopolymer matrix was verified in terms of pore distribution studied by means of mercury intrusion porosimetry. The study revealed a tendency to increase pore size and cumulative pore volume with rising temperature, which is reflected in mechanical properties. It has been also shown the possibility of monitoring the geopolymerization reaction by means of Infrared Spectroscopy.