Elaboration, caractérisation physique et hygrothermique de composite Bio-sourcés dédiés à des applications d’enveloppe des bâtiments.

Abstract

This thesis work focuses on the thermal performance of biosourced materials of plant origin with the aim of using them as thermal insulation in buildings. We have studied their use, particularly in subtropical climates. The research was conducted on wheat straw fibers. Where Wheat straw fibers were used in bulk, that is to say without chemical binder. The objective is to provide a simpler application with little processing of raw products in order to make insulation accessible to people with extremely low incomes who live in makeshift or basic housing. The plant resource used in our work is considered waste, and the recovery of this renewable material is free in Algeria. We were able to see the physico-chemical and morphological characteristics of the fibers thanks to the characterization procedures used in the experiments we carried out. In this research work, the high cellulose content of wheat straw gives it a high absorption capacity. Where Chemical analysis using the FTIR method revealed that cellulose, hemicellulose and lignin make up the fiber of wheat straw. The amorphous nature of hemicellulose and lignin was discovered by X-ray diffraction. According to observations made with a scanning electron microscope (SEM), the fibers are cylindrical and have an irregular shape with a few threads, cells and pores which allow them to adhere well to the plaster. Composites constructed from wheat straw fibers cannot be processed at temperatures above 220°C. Thermal conductivity is one of the most important characteristics of materials used in building walls. There is a decrease in thermal conductivity as the wheat straw content increases. It decreases rapidly as the proportion of wheat straw increases, until it reaches 0.324 W/m.K for 15% wheat straw, and the percentage decrease is 20.6%. in general, cause a reduction in density and the formation of porosity in the samples. The time difference of a wall with various configurations is influenced by the thermophysical parameters of the material, the thickness and the orientation of the wall. There is an inverse relationship between time lag and that of thermal energy and thermal diffusion. Increasing the proportion of wheat straw in the plaster samples resulted in an increase in thermal resistance as well as an increased time lag. Plaster containing 15% wheat straw has good thermal performance and better performance in terms of energy saving. The compound of plaster and wheat straw has low thermal conductivity and energy savings of 20.6% compared to pure plaster. This is due to the proportion of natural fibers incorporated into the compound. Although the results are important and the model obtained from the envelopment of new materials in this research, further research still needs to be done for more specific characteristics based on this research. Here are the recommendations for future work : In terms of perspective, we want to encourage the production of vegetable fiber panels because they are more environmentally friendly than conventional insulating materials. This will help reduce or even completely eliminate the use of synthetic items. In order to apply plant fiber panels directly on the walls of buildings, we will have to envelop a process for their manufacture that does not require chemical binders. 1. Develop a research program with the same experimental test that can be carried out and wrapped using different natural fibers 2. To develop an investigation on the effect of fiber on the thermal response, the cyclic loading of composite materials. General Conclusion and perspectives 3. Study simulation models to predict mechanical properties and cracks with the finite element method. 4. Apply the results of research conducted on building materials products.