Effect of different mixture parameters on the setting time of fly ash/rice husk ash-based geopolymer mortar

¹ Department of Engineering Sciences, University of the Free State, South Africa
² Department of Civil Engineering, Nelson Mandela University, South Africa

^* Corresponding author: naghizadeha@ufs.ac.za

Abstract

The present study investigated the effects of different mixture parameters on the setting time of fly ash/rice husk ash – based geopolymer mortars. Mortar mixtures were prepared using fly ash and rice husk ash as the raw material, activated using a blended alkali activator solution consisting of sodium hydroxide (SH) and sodium silicate (SS). The concentration of SH was varied from 10M to 14M, while the SS/SH ratio was varied to 1.0, 1.5 or 2.0. The ratio of alkali activator solution to binder (A/B) was also varied from 0.45 to 0.55. Fresh mortar mixtures were subjected to setting time measurement at curing temperatures of 80 °C. Cubes of 50 mm size were also prepared and subjected to compressive strength testing at different ages. Results showed that increases in both parameters comprising SS/SH ratio and SH concentration resulted in reduction of setting time, while rise in A/B ratio led to increase in setting time of mortars.