Accelerated microwave curing of hybrid geopolymers with nano-silica for enhanced physico-mechanical properties

This paper presents the microwave curing method as an alternative to conventional thermal curing of hybrid (fly ash-slag) geopolymer mortars (GMs) to achieve comparable performance with significantly reduced curing times. This study aimed to ascertain the impact of varying nano-silica contents (0.5%, 0.75%, and 1%) on the geopolymer matrix to identify the optimal dosage for enhancing densification and bond improvement phases. Mixture proportions were designed to achieve high mechanical and durability performances. The activator/binder (A/B) ratio was set at 0.71, the sodium silicate to sodium hydroxide ratio at 1.5, and the sand/binder (S/B) ratio at 2.5. This study considered two curing methods: thermal curing at 80 °C for 24 hours and microwave curing at 119 W for 3 minutes. The latter method produces equivalent thermal effects in a significantly shorter time. Physical properties tested after seven days included water absorption, porosity, and mechanical properties related to compressive and flexural strength. The results demonstrated that incorporating NS markedly enhanced the physical and mechanical characteristics. Moreover, microwave curing has been identified as a promising approach for producing hybrid geopolymers, offering a low-energy and high-performance alternative.