Self-Healing Glass/Metakaolin-Based Geopolymer Composite Exposed to Molten Sodium Chloride and Potassium Chloride

Abstract

Geopolymers (GP) are a class of X-ray amorphous, nanoporous, nanoparticulate materials that can be mixed, poured, and cured under ambient conditions. Typically, geopolymers are made using a Group 1 (G1) alkali activator such as sodium or potassium metasilicate and an aluminosilicate precursor. An analogous material to GPs is ordinary Portland cement because of the similarities in processing, however, the resulting microstructure is more similar to that of a glass. Geopolymers are more thermally stable than OPC and can therefore be used in a variety of thermal energy storage systems, as energy storage is an increasing global concern. In this study, potassium metakaolin-based geopolymer composites containing glass particles and alumina platelets were manufactured, heated in air, and exposed to molten sodium chloride or potassium chloride under an air atmosphere. Results showed the formation of an amorphous self-healing geopolymer composite (ASH-G) that could contain molten G1 chlorides for over 200 h without signs of macro or microscopic chemical degradation. The filling of cracks by glass particles in the composite after heating to 850 °C makes this material self-healing. It was found that the morphology of ASH-G composites was more affected by temperature and duration than contact with corrosive molten chlorides in air. Future works include investigating the effect of molten salt on mechanical properties during initial heating, after prolonged heating, and the material compatibility with other molten Group 1 chloride eutectics.

Analytical Review of Geopolymer Concrete: Retrospective and Current Issues

“…Although the above methods for creating self-healing materials are applicable to both conventional concrete and geopolymer concretes, the latter are known for significantly higher resistance to high temperatures, which opens up additional possibilities. Thus, researchers [ 211 ] proposed adding glass particles and aluminum oxide plates to a geopolymer mixture based on metakaolin. As a result, when the hardened geopolymer composite was exposed to a temperature of 850 °C, the cracks were filled with glass particles.…”

“…Results of research on self-healing technologies applicable to geopolymer concrete[202,203,[206][207][208][209][210][211].…”