Effect of elevated temperature on mechanical properties of ceramic brick and metakaolin waste-based geopolymer mortar

The exponential growth of the construction industry has resulted in a corresponding increase in CO2 emissions, driven by rising demand for concrete and other materials. Consequently, there is a growing demand for sustainable building materials, including alkali-activated materials. From a safety perspective, alkali-activated material systems demonstrate superior fire durability characteristics compared to conventional concrete systems. This study examines the reaction of geopolymer mortar systems to elevated temperatures and the extent to which mechanical properties are influenced. The geopolymer compositions are comprised of two precursors: ceramic brick and metakaolin waste. There has been an increasing substitution of ceramic brick waste with waste metakaolin, with replacement ratios spanning a range from 20 % to 100 %. The alkaline activator comprised sodium hydroxide (NaOH) in a water-based solution; dosage based on the Na2O/Al2O3 ratio (1.00-1.04). The geopolymer system was investigated through the use of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) for the purposes of mineralogy and microstructural analysis. The residual compressive strength of geopolymer mortar specimens was determined following exposure to temperatures of 300, 600, and 900 degrees C. The findings indicate that the selected precursor materials are appropriate to produce temperature-resistant geopolymer mortar, as all compositions remained a strength of over 50 % and exhibited no spalling effect following a 900 degrees C treatment. Additionally, an impressive increase in compressive strength was observed when the precursor was solely ceramic brick waste, with a 101.8 % enhancement due to secondary geopolymerization, which induces a sintering effect leading to a more compact geopolymer microstructure.