Abstract

This study assesses the mechanical performance of metakaolin-based geopolymers reinforced with refractory aluminosilicate particles and fibers, after exposure to elevated temperatures. Compressive strength, shrinkage and flexural strength data reveal that the inclusion of refractory particles, both with and without additional refractory fibers, promotes improved post-exposure compressive and flexural strengths compared with samples without reinforcement. Specimens exposed to temperatures between 600 °C and 1000 °C exhibited reduced shrinkage with the inclusion of higher contents of particles and fibers, while retaining good mechanical strength. This behavior is attributed to the cracking control achieved in these materials, which contributes to the enhancement of their volumetric stability through the combined effect of a strong interaction between reinforcing particles and the matrix leading to crack deflection, and the potential densification of the matrix–fiber interface at increased exposure temperatures, rising the stiffness of the final composite. These results indicate that metakaolin-based geopolymer composites, if designed with the correct compatibility between matrix and filler characteristics, can act as an inexpensive castable composite refractory.