Thermal Characterization of an Eco Conce Based on Lateritic Gravel, Millet Pods and Cement

Abstract

To simultaneously meet the need of thermal confort and living environment protection, vegetable biomass valorisation in building sector is of particular importance. In this context, the main objective of this study is to produce a lightweight composite concrete based on millet pods and lateritic gravel with a cement matrix for use in buildings to help improve thermal comfort and protect environment. To achieve this, the composite formulation with 250 kg.m-3 cement dosage and an 0.8 water to cement ratio was used to manufacture two type test specimens of (4 × 4 × 16) cm3 dimensions for porosity tests and (4 × 4 × 5) cm3 for thermal tests with a millet pod rate varying from 0 to 6% with a step of 2%. Average thermophysical characteristics of 5 tests carriesd out over 5 days, namely: Thermal conductivity, thermal diffusivity, thermal effusivity, thermal phase and damping, were experimentally measured using fluxmetric method similar to that of mini hot plate method with two Peltier elements as fluxmeters. Results obtained showed that for 0, 2, 4 and 6% millet pods dosage, thermal conductivity values obtained are respectively 1.18 W.m^-1.K^-1, 0.74 W.m^-1.K^-1, 0.63 W.m^-1.K^-1 and 0.61 W.m^-1.K^-1, i.e., a reduction of 93.44%. For same millet pod dosage, thermal effusivity values are 2157.33 J.m^-2.K^-1.s^-0.5, 1236.34 J.m^-2.K^-1.s^-0.5, 946.03 J.m^-2.K^-1.s^-0.5 and 775.04 J.m^-2.K^-1.s^-0.5, i.e., a reduction of 64.07%. On the other hand, it was observed 3.00.10^-7 m2.s^-1, 3.56.10^-7 m2.s^-1, 4.47.10^-7 m2.s^-1 and 6.25.10^-7 m2.s^-1, i.e., an increase of 108.33% for thermal diffusivity. With regard to dynamiquc thermal characteristics, it was obtained an increase from 5.43 to 13.18% for thermal damping and, from 61.00 to 84.20 min for thermal phase. Through on the one hand, thermal conductivity and effusivity decrease and on the other hand, thermal damping and phase shift increase, it is retained that characterized eco-concrete should contribute to thermal losses limitation, energiy saving and improved thermal comfort.