Influences of additives on the properties of geopolymer matrix composites (GMCS) for high-temperature applications (1150 °C)

Abstract

In this study, the influence of different additives on a geopolymer matrix composite (GMC) was explored as an alternative to a ceramic matrix composite (CMC) for thermostructural applications. Different GMCs using an N610 textile (10 × 10 cm2) and various additives (SrCO3, BaCO3, BaSO4, MgO and Al2O3 and mullite-rich powder) were cured under 6 MPa at 120 °C for 2 h. The mechanical, microstructural and structural data of the composites were compared with those of the geopolymer matrix after thermal treatment at 1150 °C. The results showed that the addition of alkali-earth barium carbonate or sulfate to the geopolymer matrix facilitated the formation of alkali-earth aluminosilicate crystalline phases and a higher viscous flow apparition temperature (990 °C), which did not enhance its mechanical properties (50 MPa) due to poor impregnation of the textile. Refractory additives such as MgO and Al2O3 in the geopolymer matrix support fiber impregnation with a low-viscous-flow apparition temperature (865 °C) and the formation of crystalline phases such as forsterite, spinel and sapphirine, which act as reinforcements, allowing a flexural strength up to 80 MPa. The addition of a refractory compound, such as mullite, leads to better embedding of fibers and a flexural strength reaching 100 MPa. To conclude, mixing the geopolymer matrix with refractory compounds results in a successful thermo-structural geopolymer composite.

Keywords

• Geopolymer
• N610
• Composite
• Temperature
• Solid-state reaction