Mineralogical, Chemical, Geotechnical and Mechanical Investigations of Bafang Lateritic Fine Soils Formed on Basalts (West-Cameroon) for Road Embankment Purpose

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.