Water content dependence of the porosity, density and thermal capacity of 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 porosity, the density and the thermal capacities of these bricks as a function of their water and millet contents. Samples having five different millet mass contents Y   (from 0 to 0.122kgmikgla-1) with dimensions 10 × 10 × 3 cm3 were first fabricated. A pycnometer suited to the samples dimensions was constructed and calibrated. Then, it was used to measure the porosity of the five dried samples. An asymmetrical hot plate device was used to measure the thermal capacity of these samples with their water content varying from 0 to a maximum value of 0.1kgdmkgw-1. An adapted device was developed to prevent water evaporation on the lateral faces of the samples. Both density and thermal capacity were modeled and the experimental results were processed to evaluate separately the density and the thermal capacity of laterite and of millet. The models enabling the estimation of the density and of the thermal capacity of the samples as a function of the millet and water contents was found to be in good agreement with the experimental results.

► Earth based bricks with millet additive are used for building in Senegal.
► Thermophysical properties are measured for different water and millet contents.
► Porosity is measured with a Helium pycnometer.
► Thermal capacity is measured with a hot plate method developed for wet materials.
► Density and thermal capacity are well represented by the proposed models.