Citation :

Iynthezhuthon Krishnamoorthy, Ganapathy Subramanian L. R, "Thermal Evolution and Comparative Stability of Metakaolin-Based Geopolymer Matrices for High-Temperature Composite Applications," International Journal of Civil Engineering, vol. 13, no. 6, pp. 351-365, 2026. Crossref, https://doi.org/10.14445/23488352/IJCE-V13I6P124

Abstract

Metakaolin-based geopolymers are being considered for applications requiring thermal resistance and structural stability at elevated temperatures. However, multiple formulations have been reported for comparative thermal evaluation studies; comparing formulations prepared under controlled activator conditions remains relatively limited. In this present study, twelve metakaolin-based geopolymer matrices were prepared by varying sodium hydroxide concentration, sodium silicate-to-hydroxide ratio, and precursor composition. Based on prior FTIR, XRD, and SEM characterization, six matrix formulations (C, D, E, F, G, and I) were selected for further detailed thermal investigation. Thermogravimetric Analysis (TGA–DTG) and Differential Scanning Calorimetry (DSC) were conducted over a temperature range of 30 °C to 1000 °C under an inert gas atmosphere to estimate mass-loss behaviour, thermal transitions, and structural stability of all the matrices. All the matrices exhibited thermal decomposition at various stages related to moisture release, dehydroxylation, and structural transformation due to high temperatures. Thermal analysis was observed among the six formulations. Sample I showed the lowest mass loss and the highest residual Mass (87.96%), representing greater thermal stability when compared to other samples. In comparison, Sample C exhibited higher mass loss and a highly reactive amorphous aluminosilicate network, which was identified through previous structural analyses. Based on TGA–DTG and DSC results, the overall thermal performance of the six geopolymer matrices was established as I > D > E > G > F > C. The findings show that the alkaline activator and precursor composition mixture strongly affect the thermal behaviour and microstructural development of the geopolymer matrix during heating. This study offers a simple method for evaluating thermal stability of geopolymer matrices and supports the selection of suitable matrices for the future development of fibre-reinforced geopolymer composites.

Keywords

Metakaolin-based geopolymers, Thermal stability, Thermogravimetric analysis (Tga–Dtg), Differential Scanning Calorimetry (Dsc), Alkali activation, High-temperature performance.

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