Influence of structural and thermophysical parameters of insulating aggregates on the effective thermal conductivity of lightweight concrete

International audience; Understanding how structural features influence effective thermal conductivity is an essential step towards the optimization of heterogeneous materials. Generally, thermal conductivity models link the internal structure to the effective thermal conductivity, with the volume fraction as the only parameter that takes into account the internal structure. Yet, the real internal structures of materials are often too complex to be accurately characterized by the volume fraction only. In this study, the influence of three parameters - the particle size, volume fraction, and thermal conductivity ratio of the constituents - on the effective thermal conductivity of concrete is evaluated. Two-point correlation and lineal path functions are used to characterize the internal structure generated by the Random Sequential Addition (RSA) model. A finite element model is developed to evaluate the effective thermal conductivity of concrete. The results demonstrate that the internal structure of concrete is dependent on the volume fraction of the inclusions, and also of the particle size. However, for volume fractions less than 20%, the effective thermal conductivity is dependent only of the volume fraction and thermal conductivity ratio of the constituents.