Measurement and modelisation of the thermal conductivity of a wet composite porous medium: Laterite based bricks with millet waste additive

Millet waste is traditionally and empirically mixed with laterite for bricks fabrication in Sahelian countries, particularly in Senegal. The aim of this paper was to characterize the thermal conductivity of these bricks as a function of their water and millet contents. Samples having five different millet mass contents Y (from 0 to 0.122 kgmi kgla−1) with dimensions 10 × 10 × 3 cm3 were first fabricated. An original asymmetrical hot plate device was developed and modeled to measure the thermal conductivity of these samples, with their water content varying from 0 to a maximum value of 0.1 kgw kgdm−1. An adapted device was developed to prevent water evaporation on the lateral faces of the samples. A new model based on a physical approach of the repartition of air and water inside the solid structure was built. It leads to a more accurate representation than other classical models of the measured variations of the thermal conductivity with the water and millet contents.