Thermophysical Properties of Metakaolin Geopolymers Based on Na_2SiO_3/NaOH Ratio

摘要

In the present work, the effect of different sodium silicate-to-sodium hydroxide ratio on the physical, mechanical and thermophysical properties of metakaolin geopolymers (MkGPs) was investigated. Geopolymers were prepared by activating the metakaolin with a mixture of NaOH and sodium silicate (Na_2SiO_3). The products obtained were characterized after 28 days of ageing. The density, porosity, compressive strength, thermal conductivity (TC), thermal diffusivity and specific heat capacity were determined. In general, the Na_2SiO_3/NaOH ratio has a significant effect on the compressive strength of the MkGPs. The thermal conductivity, thermal diffusivity and specific heat of MkGps measured in this work were in the range between 0.44 to 0.92 W/mK, 0.22 to 0.44 mm~2/s and 1 to 3.7 MJ/m~3K respectively. The highest compressive strength was 32 MPa achieved with Na_2SiO_3/NaOH ratio of 1.0. This mix has the best thermophysical performance due to low thermal conductivity, low thermal diffusivity and high specific heat compared to the other alkaline activator ratios. The results showed that the geopolymer is able to be used as the thermal insulating material.