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.
ABSTRACT:Cracking of masonry and plastering mortars of clay brick wall was a major problem in the hot climate area. The problem was the worst for the wall made of lightweight blocks. In this research, masonry and plastering mortars made from Portland cement, fly ash, expanded perlite, mortar plasticizer, and sand were tested. The testing program included the determination of water demand, setting time, water retention, compressive strength, splitting tensile strength, density, and elastic modulus. For the masonry mortar, the mixes with high calcium fly ash with or without plasticizer could be used with required properties and reduced cost. The mix of expanded perlite gave water retention over the required 70%. The mix containing fly ash and 0.2% plasticizer gave water retention slightly less than 70%. It was recommended that the mix with expanded perlite should be used for indoor plastering and the mix with fly ash and plasticizer should be used for outdoor plastering.
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