Adding Hydrated Lime in a Material Made of Clayey Soil and Fibres: Formulation and Effects on Thermo-Mechanical Properties

Abstract

In this study, we have focused our investigations on effect of adding hydrated lime on a locally made composite material, based on clayey earth (soil) and Hibiscus sabdariffa fibres, for envelope (walls) in the building. Prior to sample’s formulation, we selected an appropriate mineral (soil) material based on criteria as: plasticizer power for good workability, dense coarse particles to withstand loads and finally porous structure to take advantage of air insulating character. We then formulated, following a mixing process by shearing and compaction by vibration that we recommend, two composite materials (A), (B) which contain respectively 1% Fibres plus 1% lime, 1% Fibres plus 3% lime. We determined thermal properties by the mean of KD2 Pro thermal analyzer, compression strength accordingly to the standard NF P 18-406, porosity following volumetric and gravimetric methods and pH of soil-hydrated lime solution. As results, up to 5% of hydrated lime, the measured pH is inferior to 12: mineralization of vegetal fibres is highly unlikely. Moreover, we observe that the addition of hydrated lime resulted in a reduction in the number of cracks and their depths; Samples (A) and (B) have a rather compact appearance than the case 1% Fibres without lime (material (C)). Furthermore, with lime stabilization, the insulating potential is improved while the thermal inertia has been deteriorated compared to material (C). However, compressive strength decreases with lime, which could be due to the presence of fibres that would inhibit the hardening of the lime. At last, with 3.39% ± 3.07% MPa, 2.27% ± 11.30% MPa for samples (A), (B) respectively, the minimum required by CRATerre-EAG (guide of CDI, 1996) for construction of envelope (walls) of single storey (ground floor) buildings is met.