Multi-scale composite models for the effective thermal conductivity of PCM-concrete

•An analytical model was developed to predict the effective thermal conductivity of concrete with phase change materials.•Multi-phase, multi-scale internal structural models were combined with generalized self-consistent model.•The model unveiled that the configuration of the internal structure for the PCM phase is very important.•The PCM phase must be considered as a thin shell matrix in the model for predicting the effective thermal conductivity.•Physically, the PCM can effectively block the heat flow and thus reduce the thermal conductivity. Encapsulated phase change materials (PCMs) were used in concrete to improve thermal properties of the concrete, called PCM-concrete. This paper presents the predictions of the effective thermal conductivity of PCM-concrete using different composite models, such as the parallel, the series models, Maxwell model and Generalized Self-Consistent (GSC) model. Multi-phase, multi-scale internal structural models were developed and combined with GSC model to predict the effective thermal conductivity of PCM-concrete. It was found that the configuration of the internal structure for the PCM phase is very important. The PCM phase needs to be considered as a matrix (a thin shell), which can effectively block the heat flow and thus reduce the thermal conductivity of PCM-concrete. The GSC model with the suggested internal structure model can predict the effective thermal conductivity of PCM-concrete. The prediction agreed with test data quite well, and the prediction is within the upper and lower bounds.