SHEAR BOND STRENGTH OF FA-PC GEOPOYLMER UNDER DIFFERENT SAND TO BINDER RATIOS AND SODIUM HYDROXIDE CONCENTRATIONS

This paper presents the effects of sand to binder (S/B) ratio and sodium hydroxide (NaOH) concentration on setting time, compressive strength, and shear bond strength of fly ash (FA)-Portland cement (PC) geopolymer binder. Geopolymer binder is manufactured from FA and PC at the ratio of 90:10 by weight of binder. The liquid alkali solution used in this study are sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solutions. The Na2SiO3/NaOH ratio of 2.0, liquid alkali solution/binder ratio of 0.60, and curing at ambient temperature are fixed in all mixes. The differences in NaOH concentrations of 5, 10 and 15M and S/B ratios of 1.00, 1.25 and 1.50 has been investigated. Test results show that the differences of NaOH concentration and S/B ratio has an effect on setting time, compressive strength and shear bond strength of FA-PC geopolymer mortar. The setting time of mortars are obviously decreased with increasing of S/B ratio whereas the setting time of mortars are obviously increased with increasing of NaOH concentration. The compressive and shear bond strengths of mortars increase as increasing of both S/B ratio and NaOH concentration up to a threshold limit. The highest slant shear strength between Portland cement concrete substrate and FA-PC geopolymer mortar is found in the mortar with 1.25 S/B ratio and 10M NaOH concentration which gives 24.1 MPa.