Thermal Performance of Metakaolin-Based Geopolymers: Volume Stability and Residual Mechanical Properties

Abstract

This chapter describes how a series of metakaolin (MK)-based geopolymer specimens measuring 50 mm cubes with different Si/Al ratios were prepared and exposed to different heating profiles in an electric furnace. The crumbling of cement paste into small pieces while geopolymer specimens retained satisfactory compressive strengths points towards the potential of geopolymers to perform soundly as a fire resistant material and also the need to impart sufficient volume stability and strengths when subjected to high temperatures. On exposure to elevated temperatures, geopolymers either retain their amorphous condition or transform to a crystalline microstructure in an experiment. The general agreement based on previous research is that geopolymers possess a stable inorganic framework subject to elevated temperatures unlike OPC which suffers breakdown of its hydration products. The dissolution of fumed silica into sodium hydroxide solution was done to obtain a clear solution. Solutions were stored for about 24 hours before use to allow them to cool down to room temperature and to achieve equilibrium.