Effect of moisture-induced disintegration on the thermal conductivity of aggregated clays

Clay particles typically bond together to form aggregates, resulting in a double-porosity structure. As water content increases, coarse aggregates may disintegrate into finer clay particles. However, both the disintegration process and the double-porosity structure are rarely considered in existing thermal conductivity models. In this study, the thermal conductivity of aggregated clays is analyzed using homogenization theory and the disturbed state concept (DSC). A reference model is first developed to describe the thermal conductivity of dry aggregated soils, incorporating a structural parameter to account for the effect of inter-aggregate pores. This model is expressed as a function of the thermal conductivities of air and clay particles within a homogenization framework. To capture the effects of saturation and aggregate disintegration, a disturbance factor is introduced. Based on the DSC, a new model is proposed that integrates the combined effects of inter-aggregate porosity and aggregate disintegration. A simplified version of this model is derived by assuming complete aggregate disintegration at full saturation, requiring only three parameters for practical application. The disintegration process is validated through mercury intrusion porosimetry (MIP) tests, which reveal that the disturbance factor follows an inverse S-shaped trend with respect to the inter-aggregate pore ratio. Validation of the proposed model using both experimental results and data from the literature demonstrates its effectiveness in predicting the thermal conductivity of various types of aggregated clays across a wide range of saturation levels.