Influence of TiO2 nanoparticles (wt%) onto the physical and mechanical properties of the TiO2-geopolymer paste

Abstract

The TiO2-geopolymer paste had been prepared by dry-mixing of the fly ash with various concentration (wt%) of TiO2 nanoparticles (2.5%, 5.0%, 10.0% and 15.0%). Those powder mixtures were then mixed with the alkali activator with the ratio of 2.5 and were cured at room temperature for 28 and 640 days. The phase and chemical bonding analysis revealed that the incorporation of TiO2 nanoparticles did not create any additional phase or functional group, but only physical interaction might have occurred in between the TiO2 and geopolymer matrix. However, the physical properties were depending on the TiO2 nanoparticles content where setting time of the geopolymer can be shortened by the addition of certain amount of TiO2 nanoparticles (up to 5.0 wt%). The water absorption also increased as a function of TiO2 content, due to the formation of the micro cracks as a result from the agglomeration of TiO2 nanoparticles. The compressive strength reaches its maximum value, 85.9 MPa with 5.0 wt% of TiO2 nanoparticles. Beyond 5wt%, the strength decreased almost half of the maximum value, where agglomeration becomes a main factor. While for 640 days of ageing, sample with 15.0 wt% shows triple increment from 30.6 MPa to 95.3 MPa.