Effect of Pore Morphology on the Thermal Conductivity of Geopolymer Foam

Geopolymers are considered an alternative to conventional cement recently. The use of fly ash and blast furnace slag in geopolymer, which are waste products considered as an environmentally friendly product due to the solution to the storage of wastes also. Geopolymer concrete production is also reported to be 44-64% less than the cement that causes the most CO2 emissions. CO2 emissions are reduced due to the minimum processed natural minerals and industrial waste products used in the geopolymer system. For this reason, this study comes to the fore in terms of the evaluation of wastes. Production of porous geopolymers is potential in use in many industrial applications such as filtering, thermal insulation, light structural material, and catalysis. By controlling the pore type, pore size distribution, pore connectivity, and shape of porosities, potential usages are differentiated. In this study, closed porosity geopolymer foams were produced by the geopolymerization technique with the help of hydrogen peroxide and calcium stearate (CaS) as a surfactant. The thermal conductivity, density, and strength values was correlated with the changing pore size distribution depending on the amount of surfactant and foaming agent. In this study, porous geopolymers with density values 450-500 kg/m3, 0.069 W/mK thermal conductivity, and 2.1 MPa strength value was reached. The reduction in pore sizes due to CaS increase was analyzed. However, we did not observe a decrease in thermal conductivity values due to the reduction of the pore size. Exciting results for CaS content on thermal conductivity were reported.