Modelling of the thermal conductivity of the lightweight concrete on the coarse aggregate
The article presents a detailed analysis of the mathematical models for the determination of the thermal conductivity of two-phase systems. Such systems include lightweight concrete, in which large filler is considered as the dispersed phase in the sand cement matrix. The complexity of the calculation of thermal conductivity of such systems consists in the chaotic distribution of heat-insulating materials (large filler) in the volume of concrete. The calculation results have allowed to receive the regression equation of thermal conductivity of lightweight concrete and to quantify the impact of cement-sand mortar, large filler on the effective thermal conductivity of lightweight concrete. Examined some calculation models determining the thermodynamic characteristics of the material as the complex structure, and on the basis of the model of an «elementary cell». According to the results of theoretical calculations it was found that the determination of the material thermal conductivity of the complex structure is enough to reduce complex configuration of the material to «elementary cell». Such calculation method significantly allows to simplify the solution to a problem of definition of thermal conductivity of light concrete with chaotically distributed large filler of the various form.