Development and thermomechanical characterization of bio-based construction materials made from industrial cotton waste

Résumé

The building sector represents around a third of global energy consumption and greenhouse gas emissions, largely due to architectural design, building envelopes and the materials used. This situation highlights the need for sustainable solutions to limit its environmental impact. At the same time, the cotton industry in Benin is booming, generating significant by-products that are still under-utilised and represent an ecological threat. This research aims to recover these wastes in order to develop bio-based building materials that can help reduce the energy consumption of buildings. The main objective is to evaluate the physical, mechanical and thermal properties of concrete incorporating fibers from cotton ginning, to determine their suitability for different applications. The experimental approach is based on the characterisation of the by-products (water content, absorption, density, calorific value), followed by the design of concrete mixes using the Dreux-Gorisse method, with incorporation rates ranging from 0.1% to 0.8% by mass (BF-00 to BF-08). The results reveal a gradual decrease in the density of fresh concrete, from 2.181 t/m³ (BF-00) to 1.963 t/m³ (BF-08), confirming their lightness. The Abrams cone slump indicates reduced workability, decreasing from 70.33 mm to 64.33 mm. In terms of mechanical properties, compressive strength decreased from 14.131 MPa to 7.025 MPa, with a significant reduction above 0.2% fibre content. However, tensile and flexural strengths reach their best values between 0.2% and 0.4%, or 1.55 MPa and 3.753 MPa respectively. On a thermal point of view, adding fibers really improves performance. The thermal conductivity decreases from 1.022 W/m.K to 0.448 W/m.K and the thermal diffusivity from 5.647×10-7 m²/s to 2.191×10-7 m²/s, confirming the suitability of these lightweight concretes for insulation. Formulations BF-00 to BF-02 are suitable for load-bearing walls, BF-04 to BF-06 for non-load-bearing walls and infill elements, while BF-08 offers the best performance for insulation. In short, the incorporation of cotton by-products is a highly promising approach to the development of building materials with low environmental impact. However, further studies on durability and behavior in real conditions are needed to confirm their potential in sustainable construction.

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