Effects of water to solid ratio on thermal conductivity of fly ash-based geopolymer paste

Thermal conductivity is one of the most important properties of material when applied as an insulating material. It referred to how much heat can be transferred inside the material. Usually, a low thermal conductivity is needed as a good insulating material. This study focuses on the effect of various water to solid ratio on the geopolymers' thermal conductivity. Six various waters to solid ratio ranging from 0.16 to 0.31 were studied. Mix design of geopolymers paste using fly ash as aluminosilicate was obtained from Paiton power station. Alkaline activator was combined with NaOH concentration of 10 M and constant Na2SiO3/NaOH ratio of 2.0. A maximum of 7 days compressive strength obtained was up to 34.12 MPa when water to solid ratio at 0.22. The thermal conductivity was varied with a temperature range from 50°C to 200°C. The average thermal conductivity of geopolymers paste ranges from 0.75 to 1.54 W/m.°C. The lowest thermal conductivity occurred when water to solid ratio was at 0.22. Based on this finding, fly ash-based geopolymer paste can be applied as an insulating material.