Effect of the Number and Orientation of Fractures on the P-Wave Velocity Diminution: Application on the Building Stones of the Rabat Area (Morocco)

This study is focused on two types of Moroccan rocks, among the most widely used as building stones: the calcarenite of Salé (CS) and the marble of oued Akrech (MA). The two rocks, lithologically different, show a clear contrast of their P-wave velocities (Vp): 3.90 vs 5.10 km/s at dry state and 4.29 vs 5.64 km/s at saturation. The “Artificial fractures” created in the two rock types reveal that their Vp undergo diminutions which the rates vary depending of the number and the plane orientation of the fractures. In the CS, Vp shows an increasing of cumulative diminution (Dc) according to the number of fractures, but with a variable rate of unitary diminution (Du) from one fracture to the other. This defines a linear regression with a low coefficient of determination (Dc = 10.18NbFr + 10.96;r2 = 0.87). The mode of the Vp evolution would be related to the roughness of fractures surface, which itself depends upon the petrographic nature of the calcarenite (friable structure, high porosity and heterogenous composition). The MA manifested an increasing Dc with a fairly constant rate of Du from a fracture to another, giving a regression line with a high coefficient of determination (Dc = 12.17NbFr – 10.69;r2 = 0.99). This steady diminution of Vp would be related to the granoblastic texture and the monomineral composition of the marble, which engender smoother fracture surfaces. The rates of Vp diminution also depend on the orientation plane of the fractures relative to the direction of wave propagation. The fractures parallel (θ = 0°) amplify slightly the Vp, playing a significant role of “waveguide”. The fractures oriented at 45° lead to a diminution lower than those of fractures oriented at 25° and 90°. The same trend of diminution, but at variable rates, appears on the samples of the two types of stones at dry and saturated state. This can be explained by the compressive nature of P-waves, which obey the physic laws of the transmission of the constraints in the solid mediums.

Effects of Lizardite Addition on Technological Properties of Forsterite- monticellite Rich Ceramics Prepared from Natural Magnesite and Dolomite

Lizardite rich peridotite has never been used to prepare ceramic specimens,especially in Morocco.For this raison,potential use of naturally abundant lizarditic material from the Rif domain,as a supply for ceramic industry,has been evaluated.The effects of lizardite addition to magnesite and dolomite mixtures on the thermomechanical properties of the calcined ceramics were also detailed.To achieve this target,natural lizardite,magnesite and dolomite samples were collected in ultrabasic Beni Bousra massif.Those raw samples were used for the synthesis of a forsterite-monticellite rich ceramics.Both raw and sintered samples were characterized by x-ray diffraction,scanning electron microscope and fourier transform infrared.The obtained results showed that both magnesite and dolomite were mainly composed of MgCO_(3) and CaCO_(3).In contrast,lizardite sample showed high amounts of SiO_(2),MgO and Fe2O_(3).An increased amount of lizardite in the initial mixtures enhanced mechanical and dimensional properties of the prepared ceramic specimens,and subsequently,the production of ceramics with the required technological properties.Thus,the preparation of Moroccan lizardite-based ceramics is technically feasible,economically justifiable and socially desirable due to the contribution to the economic growth of the raw materials sector,especially ceramic industry.