No abstract

The present paper treats the relationship between geotechnical parameters and the mineralogical compositions, in order to understand the behavior of the Bafang lateritic fine soils and their efficient use as road embankment materials on the other hand. Thus, the field campaigns have permitted to distinguish two facies of Bafang lateritic fine soils: reddish and yellowish facies. The X-ray diffraction (XRD), the thermo-gravimetry analysis (TGA) and the X-ray fluorescence (XRF) have revealed that the reddish facies contents: kaolinite (53.34% -48.29%); hematite (16.62% - 17.40 %); gibbsite (8.26 % - 16.54%), ilmenite (7.6 % -7.98%), quartz (1.92 % - 4.65 %), illite (2.65% - 1.99 %) and accessories minerals as florencite (1.45%); montmorillonite (0.90 %) and plagioclase (0.69 %); while the yellowish facies is composed of : 65.1 % kaolinite, 11.2 % gibbsite, 9.64 % goethite, 7.02 % quartz, 3.23 % ilmenite and 2.08 % of illite. Their Silica/sexquioxide ratios correspond to those of moderate laterite. The geotechnical and mechanical characteristics have shown that the reddish and yellowish facies are respectively silty clay and sandy silt. They are plastic to very high plastic and moderately clayey to clayey materials. Moreover, they are medium swelling to high swelling. The IBR values more than 40% and the soaked CBR values prove that these materials belong to the S4 bearing capacity class. The minimum values of UCS and Rt are respectively 1.7 MPa and 0.17 MPa. Then, the results of geotechnical and mechanical properties combining to those of XRD, TGA and XRF have demonstrated that the fine lateritic soils with low silica/sexquioxide ratios values (less than 1.6) are suitable for road embankment.

Widikum and its surroundings (North-West Cameroon) are covered with basalts, granites and gneisses. Construction companies use these rocks extensively and indiscriminately for structural loading, pavements, wall cladding as cobblestone and masonry stones. The suitability of these rocks and their petrographic (outcrops mode, structure, color, mineralogical composition and crystals size), physical and geomechanical (specific density, bulk density, Los Angeles abrasion test, and Aggregates crushing test) properties evaluation becomes important for their aforementioned applications. The aim of this study is to characterize on the petrographic and geomechanical level, basalts, granites and gneisses of the locality of Widikum and its surroundings for their use as construction materials. Concerning the petrographical point, granites and gneisses are rich in quartz, feldspar, plagioclase, biotite, amphibole and accessory minerals like opaque minerals and zircon. On the other hand, basalts are ferro-magnesians rich in olivine, pyroxene and opaque minerals. Plagioclase is also a main constituent mineral of this geological formation. On the physical and geomechanical properties, despite their extension on the field, granites have satisfactory density; but, they are least resistant according to the Los Angeles abrasion values. However, basalts are one of the geological formations which are the least extended on the field. They are most dense with the satisfactory to excellent Los Angeles abrasion values. Concerning the gneissic formation, its density and Los Angeles abrasion values are satisfactory. Generally, the aggregates crushing values of studied geological formations attest that they are satisfactory to excellent apart from those of coarse grainy granites. In view of the foregoing, basalts have the best geomechanical qualities and could be used as constituent of construction materials.