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

Abstract

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 weightof 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 curingat ambient temperature are fixed in all mixes. The differences in NaOH concentrations of 5, 10 and 15M andS/B ratios of 1.00, 1.25 and 1.50 has been investigated. Test results show that the differences of NaOHconcentration and S/B ratio has an effect on setting time, compressive strength and shear bond strength ofFA-PC geopolymer mortar. The setting time of mortars are obviously decreased with increasing of S/B ratiowhereas 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 NaOHconcentration up to a threshold limit. The highest slant shear strength between Portland cement concretesubstrate and FA-PC geopolymer mortar is found in the mortar with 1.25 S/B ratio and 10M NaOHconcentration which gives 24.1 MPa.