A novel TiO₂/Epoxy resin composited geopolymer with great durability in wetting-drying and phosphoric acid solution

A novel hybrid structured TiO₂/Epoxy resin has been prepared by a simple in-situ synthetic method, which was used to enhance alkali-activated slag/fly ash (AASF)geopolymer paste for the first time. The study examined the durability performance of the paste by exposing specimens to two aggressive conditions, including wetting-drying cycles and continuous immersions in phosphoric acid solutions for 90 days. Visual appearances, physical, mechanical properties and microstructures of samples were analysed. Besides, degradation kinetics were monitored by measuring degradation depths. The results indicate that TiO₂/Epoxy resin composite is able to improve the microstructures and limit the propagation of cracks. It is assumed that the hydroxyl groups of the epoxy resin and the bonded water in the aluminosilicate gel may form hydrogen bonds which make the binder matrix dense and homogeneous. The matrix thus intrinsically has a better fracture behavior with the existence of organic-based TiO₂/Epoxy resin compared to the inorganic-based aluminosilicate crosslinked networks. The study also revealed that compared to the AASF without the composite addition, TiO₂/Epoxy resin composited AASF exhibited a lower degradation kinetic regardless of exposure conditions. Therefore, a new direction is developed and recommended to use TiO₂/Epoxy resin to improve the durability of AASF geopolymer regarding aggressive exposure environments. In addition, the manufacturing of TiO₂/Epoxy resin composited AASF binder is relatively simple, cost-effective and eco-friendly with low carbon footprint.