Étude de la formulation et des propriétés mécaniques et thermiques du béton de balles de riz

Abstract : Everyone agrees today that human activities significantly affect the climate of the planet. The construction sector is one of the main contributors to this situation as it is the largest energy consumer and the second largest CO2 emitter in the world. It is therefore important to build eco-friendly buildings, which consume little energy and emit less greenhouse gases throughout their life cycle. The present study is then integrated into a general problem of development of innovative building materials with reduced environmental impact. We propose to use the rice husk as a vegetable aggregate in a cementitious matrix. The objective of the work is to propose a method for the mix design of concretes based on plant aggregates and to study the mechanical and thermal behavior of rice husk concrete. Setting tests on pure cement paste formulated with water resulting from the infusion of the rice husk showed that these aggregates had no inhibiting effect on the setting of the cement. To confirm this hypothesis, a chemical analysis of the rice husk was carried out and the results showed that the extractable ratio of rice husks is almost zero, unlike other plant aggregates such as hemp and wood. The proposed formulation method consists in determining the packing density of the plant skeleton for a given method of implementation and then in proportioning the binder paste which will occupy the residual intergranular pore volume. The paste is consisted of the binder, the effective water, the possible additions and admixture, and trapped air and/or entrained air. For a given volume of air (and additions), the quantities of cement and effective water are then adjusted to achieve the targeted performances, based on the law of Féret. However, for this type of concrete, the large volume of entrained air also depends on the quantity of cement and water present in the mixture, the intensity of the mixing and the casting mode. A model describing the volume of residual air was then calibrated from tests carried out with the components of the concrete that it is desired to manufacture. Finally, the problem of formulation is solved by using a numerical optimization module. In order to validate the model, the method for the mix design was applied to five samples with a target resistance of 0.5; 1; 2; 4 and 8 MPa. The performances obtained are quite similar to those targeted. In addition, it has been observed that the preservation mode of the specimens has a significant influence on the mechanical strength of the material. Indeed, a cure in desiccation condition can reduce the mechanical resistances up to 60%. The best resistances obtained were observed on the specimens preserved at 95 % RH. Measurements of thermal conductivity have shown that rice husk concrete is a very good alternative to more conventional systems in terms of thermal insulation. The average value of the thermal conductivity of the rice husk concrete varies depending on the binder dosage between 0.070 W/(m.K) and 0.171 W/(m.K). The evolution of the thermal conductivity as a function of the density and the cement dosage is linear
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Theses
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http://docnum.univ-lorraine.fr/ulprive/DDOC_T_2017_0232_CHABI.pdf
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https://hal.univ-lorraine.fr/tel-01907795
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Submitted on : Monday, October 29, 2018 - 3:01:54 PM
Last modification on : Wednesday, January 23, 2019 - 9:58:16 AM

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  • HAL Id : tel-01907795, version 1

Citation

Edem Chabi. Étude de la formulation et des propriétés mécaniques et thermiques du béton de balles de riz. Science des matériaux [cond-mat.mtrl-sci]. Université de Lorraine; Université d'Abomey-Calavi (Bénin), 2017. Français. ⟨NNT : 2017LORR0232⟩. ⟨tel-01907795⟩

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