Heat release and thermal conductivity of expanded-clay concrete for 3D printer

The subject of research is expanded-clay concrete with additives of ground granulated blast-furnace slag, silica fume, superplasticizer admixture and air-entraining admixture for 3D printing. The heat release of concrete and thermal conductivity of concrete are investigated depending on the concrete composition (cement, water cement ratio, expanded-clay), additives (slag, silica fume) and admixtures (superplasticizer, air-entraining agent). The thermal conductivity of concrete depends primarily on the expanded clay gravel content and depends less on the cement content. If both factors increase, the thermal conductivity decreases. This is due to the replacement of dense sand grains with a more porous cement paste. The influence of air-entraining admixture on the thermal conductivity of expanded-clay concrete was not detected due to the high scattering of the experimental points. It was confirmed that the cement content and water cement ratio have an impact on the integral value of the heat release per unit mass of cement (q = Q/C). This value decreases with increasing cement content. The reason for this is that the total heat generated by concrete Q, with constant W/C and other equal conditions, increases linearly with increasing the cement content. The air-entraining admixture increases the heat generation by concrete. This is due to the chemical interaction between the admixture and cement hydration products with the formation of thermodynamically more stable compounds.