Thermogravimetric assessment of network reticulation in metakaolin-based geopolymers incorporating Cr-rich industrial waste

This study proposes thermogravimetric analysis as a quantitative method to assess the degree of network reticulation in metakaolin-based geopolymers incorporating Cr-rich hazardous waste. The degree of polycondensation is assessed through mass loss associated with dehydroxylation (350–650 °C), directly linked to residual ≡Si/Al–OH groups. Increasing waste content (up to 30 wt%) leads to an 86.96% increase in dehydroxylation mass loss relative to the waste-free reference, indicating a less reticulated network and an 87% decrease in compressive strength. FT-IR analysis, supported by peak deconvolution, shows a shift of the Si–O–T band toward higher wavenumbers, a decrease in the Si–O–T/Si–O–Na + area ratio, and an increase in the Si–OH band area, consistent with a structure enriched in non-bridging oxygen. The agreement between TG/DTA, FT-IR, OH - titration, ionic conductivity, and mechanical performance demonstrates that TG/DTA provides a simple and quantitative descriptor of geopolymer reticulation and stability.