Measurement and Modelling of Water Content Effects on Thermal Properties of Compressed Soil Building Blocks

Abstract

Aims: The aim of this paper was to determine the thermal conductivity and the thermal effusivity of the compressed soil building blocks as a function of their water content. Study Design: Samples with dimensions 53x40x20 mm3 were produced for experiment. Eight containers and an oven were used to determine the equilibrium moisture content. The thermal properties of samples were obtained using a symmetrical hot strip method device. Place and Duration of Study: University of Yaounde I and National Advanced School of Engineering, Laboratory of Energizing, Water and Environment, between March 2014 and October 2014. Methodology: Thereafter, sorption isotherm of this building material was determined using the gravimetric static method of saturated salt solutions at 30°C (ambient average temperature), and GAB equation was applied to discuss the results. Then, a symmetrical hot strip method device was used to measure the thermal conductivity and the thermal effusivity of these samples, with their water content varying from 0 to a maximum value of 0.139 kgw.kgdb-1.An adapted device was developed to prevent water evaporation on the lateral faces of the samples. Results:Both thermal conductivity and thermal effusivity were modelled and the experimental results were processed to evaluate these thermal properties of compressed soil building blocks.A new simplified model, based on a physical approach with assumption of an ideal shrinkage of the material during the evaporation of water, was built. Conclusion: Calculated and experimental values of thermal properties were in good agreement, with a maximum standard error of 1.671 Wm-2K -1s1/2 for thermal effusivity and of 0.024 Wm-1K-1 for thermal conductivity. The suitability of this model for other buildings material will be further studied.