Physico-Mechanical Characterization of Clay and Laterite Bricks Stabilized or Not with Cement

This study focuses on the valuation and optimization of local materials to meet the challenge of sustainable development. Faced with climate change and the preservation of the environment, research into eco-materials is necessary to reduce the energy bill while ensuring comfort and safety. The objective is to make a comparative characterization of the physico-mechanical properties of compressed earth bricks made from local materials: clay, laterite and sand. These are, on the one hand, bricks made from clay and laterite, reinforced with a percentage of sand varying between 20% and 30% in steps of 5%., were made. On the other hand, these same mixtures stabilized with 5% cement (CEM II-32.5) are also used to produce bricks. A characterization of the raw materials was made before studying the physico-mechanical properties of the bricks themselves. This involved evaluating the water absorbency and compressive strength of stabilized and unstabilized bricks. The results show that the absorptivity of stabilized clay bricks is acceptable up to 25% sand because it is less than the 15% maximum value set by Cameroonian standard NC-104: 2002-06. However, that of stabilized laterite bricks is higher than the maximum value set by the standard. The compressive strengths, for clay bricks stabilized with 5% cement and for laterite bricks with 0% sand added, are all greater than 2 MPa and therefore are acceptable. In addition, clay bricks with 20% sand and stabilized with 5% cement are recommended because they have the most optimal physico-mechanical properties.

Geotechnical Behavior of Eastern Senegal Rock Mass Slopes by Geomechanical Classifications and Applications

In Senegal, rock mechanic studies began in last four years and were a very new engineering domain. So, the first stage is to characterize geological materials. It is on this way that this work is done. This paper analyzes geomechanical parameters of sandstones of Dindifélo and basalt of Bafoundou belonging to the Proterozoic rocks domain of eastern Senegal. By Rock Mass Rating (RMR) and Geological Strength Index (GSI), sandstones of the Dindifello Cliff show fair to poor characteristics while basalts of the hills of Bafoundou are fair quality. In addition to the qualities of rock mass, Young moduli, uniaxial compressive strengths and tensile strength of rock mass are also defined using Rock Quality Designation (RQD) GSI, RMR. Hoek-Brown parameters m and a, depend both on the fracturation and the content fine in the rock. Values of mechanical parameters are different when deduced from RMR, GSI and from intact rock laboratory test. Those differences are due to variables taken account. The variation depends also on the quality of the rock. Statistical analysis shows possible unstabilities which depend on rock mass parameters but with acceptable probability of failure. Probability of failure is the highest when deducing from Mohr criterion than from Hoek-Brown criterion.

Influence of Mechanical Properties of Concrete and Soil on Solicitations of Mat Foundation

This work studies the influence of mechanical and geometrical characteristics of the concrete and the soil on the stresses in a mat foundation. In this study, the soil-structure interaction is modeled by two parameters, the modulus of subgrade vertical reaction (k) and the modulus of subgrade horizontal reaction (2T). These two parameters are dependent on the geometrical and mechanical characteristics of the system. Results of this study show a sensitivity of solicitations to variations of geometrical and mechanical characteristics of the model. Although solicitations in the plate are sensitive to mechanical properties of concrete, these solicitations are strongly influenced by the mechanical and geometrical characteristics of the soil mass. However, it should be noted that the influence of Eb is denoted in the center of the plate whereas the Es feels almost in the same manner over the entire extent of the plate. This study also shows that for the same load cases, the values of the torsion moment and shear stress are not significant those of bending moments and normal stresses, respectively.

Metallurgical Analysis of Brake Blocks

This study focuses on the characterization of train brake blocks. The brake blocks are an essential organ of train speed control system to ensure comfort and safety to passengers and crew. However, poor quality soles can cause a premature wear of the wheels whose consequences are on the one hand, a damaged brake function, and also high repair costs. Samples were carried out on 3 different batches of brake blocks. Their metallurgical characterization consisted of a study of the hardness and microstructural analysis (microstructures and chemical analyzes) of the different samples. The results show that the hardness of some soles is greater than that of the wheel, mainly associated with a cementite microstructure. This can lead to a premature wear of the wheels at the expense of brake blocks.