The Effect of Nano-TiO2 and Nano-Al2O3 on Mechanical, Microstructure Properties and High-Temperature Resistance of Geopolymer Mortars

Considering the environmental implications of CO2 gas emitted during cement manufacture, alternative binders are still examined for sustainability reasons. Many binder materials are being used to create geopolymers instead of cement-based composites. In this study, metakaolin and slag were used to produce geopolymer mortar. In addition, metakaolin and slag-based geopolymer mortar (MSGM) specimens were produced and cured at ambient temperature. Also, nano-doped-MSGM samples were generated through the incorporation of nano-TiO2 and nano-Al2O3 at the rates of 0, 1, and 2% of the total weight of the binder materials to investigate the impact of nanomaterials on the high-temperature resistance and mechanical features of MSGM samples. For this purpose, compressive strength, bending strength, water absorption, microscopic visual evaluation, weight loss measurements, ultrasonic pulse velocity (UPV), and microstructural analyses were implemented on the MSGM specimens with and without nanomaterials before and after the exposure to high-temperature effects. As a result, MSGM samples with nano-TiO2 and nano-Al2O3 were more compact and had fewer micro-fractures at high temperatures than nano-free samples. Also, the compressive and flexural strength of nano-doped samples relative to the nano-free samples subjected to high temperatures increased up to 32.57 and 28.45%, respectively.