Effect of corundum sand proportion on strength properties geopolymer mortar based on fly ash

The main objective of this study is to investigate the possibility of replacing the traditional construction aggregate, river sand, with corundum material and to evaluate the effect of the proportion of corundum sand on the strength properties of fly ash based geopolymer mortar. Electrocorundum (white) and fly ash from a thermal power plant in Skawina were used to make the samples. Different fractions of electrocorundum were used to prepare the geopolymer mass. A geopolymer based on fly ash and river sand was used as reference material. The results showed that the average compressive strength of fly ash and alumina-based materials increased (results ranging from 25.9 to 47.0 MPa) compared to the reference samples (20.7 MPa). The flexural strength results showed a weakening of the strength properties of the electrocorundum and fly ash-based samples (results ranging from 6.1 to 4.8 MPa) compared to the reference sample (7.0 MPa). Only the geopolymer, which in its composition contained a mixture of electrocorundum with several grain gradations, showed an increase in flexural strength (7.3 MPa), compared to the reference sample. Additionally, surface topography analysis of the geopolymer samples was performed by scanning electron microscopy. The whole tests carried out on the above types of material indicate that it can be used as a substitute for sand in geopolymer mortars.