Abstract

Abstract Geopolymer is a family of alkali-activated materials that served as an alternative Portland cement. In this study, geopolymer was synthesized by using fly ash, sodium hydroxide (NaOH) solution and sodium silicate (Na2SiO3). Aluminium powder was used to create the bubble for lightweight concrete production. The compressive strength, bulk density and water absorption were tested. Thermal conductivity was also investigated. First, the effect of NaOH concentration on properties of geopolymer lightweight concrete was investigated. NaOH concentration at 7.5, 10 and 12.5 M and liquid to ash ratio (L/A ratio) at 0.5 were designed. Bulk densities in the range of 633 to 763 kg/m3 and water absorptions in the range of 22 to 31 % were also obtained. The maximum of compressive strengths at 1.7 MPa and the minimum thermal conductivity at 0.31 W/m.K were obtained. Second, the effect of Na2SiO3 to NaOH ratio at 1, 1.5 and 2 on properties of geopolymer lightweight concrete was investigated. The maximum of compressive strengths at 4.4 MPa and the maximum bulk density at 1,428 kg/m3 were obtained. Water absorptions in the range of 16 to 18 % and thermal conductivity in the range of 0.15 to 0.3 W/m.K were also obtained. The results showed that the used of NaOH incorporated with Na2SiO3 increase the compressive strength and bulk density of geopolymer lightweight concrete, while water absorption and thermal conductivity had decreased.

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