Dielectric properties and temperature profile of fly ash-based geopolymer mortar

In this paper, the fresh properties, dielectric properties and temperature profile of fly ash-based geopolymer mortars are investigated to observe the effect of mixture proportions and time after mixing. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were used as the activators. The results of fresh properties revealed that the added water could improve the workability of geopolymer mortar. It is also found that the initial and final setting times of all the geopolymer mortars are less than those of cement mortars. For the dielectric properties and surface temperature, mortars were measured during a 24-hours geopolymerisation period at room temperature. The obtained results show that dielectric properties and surface temperature of geopolymer mortars tended to decrease with increasing time after mixing. And the geopolymer mortars had the highest value of dielectric properties and surface temperature at right after mixing. In addition, the dielectric properties (εr' and εr″) of the specimens with more liquid constituents were also higher. In particular, this work shows that it is possible to cure the fly ash-based geopolymer mortars with microwave energy depending on the mixture proportion and time after mixing.