Physical and Mechanical Characterization of Unbound Granular Material (UGM) Used as Road Base Layers in Côte d'Ivoire

The aim of this study was to determine the physical and mechanical properties of Unbound Granular Material (UGM) used in road construction in Côte d'Ivoire. From each of the fifteen quarries surveyed, ten samples of gravel were taken and subjected to standardized tests covering cleanliness, bulk density, mechanical strength, grain size and bearing capacity. The results show that the mass of methylene blue (MB) varies from 0.06 to 0.10 g/100g, the apparent density (DA) from 1.44 to 1.77 t/m3, the mechanical strength indices expressed by the tests. Los Angeles and Micro-Deval tests, range from 16% to 34% and from 4.67% to 10.33% respectively. Bearing capacity is also satisfactory, with CBR values ranging from 68% to 87%. Principal component analysis (PCA) was used to distinguish five material classes. Class 1 comprises gravels with high mechanical strength and high dry density. Class 2, represented by samples from the ABSI quarry in Abidjan, has the best bearing capacity, with an average CBR of 87%. Class 3, associated with the GASI quarry in Gabiadji, is characterized by a high fines content, reaching a maximum fines content (AG) of 5.35%, and increased sensitivity to water. Class 4 corresponds to the ATAM quarry in Abidjan, which offers excellent wear resistance, with a minimum Los Angeles index of 16%. Finally, class 5 includes three quarries in Abidjan (ABIC, ATAB, ATSO) and one in Aboisso (ABOC). The gravels from these quarries have high optimum water contents, reaching values of 6.25%, and relatively low dry densities, ranging from 2.30 to 2.36 t/m3.