California bearing ratio of an unsaturated deformable pavement material along drying and wetting paths

This article presents the results of a careful laboratory programme aimed to examine the influence of initial dry density, moisture content, degree of saturation, and matrix suction on the California bearing ratio (CBR) of a pavement material along drying and wetting paths. To this end, the CBR value of a sand–kaolin mixture was measured in a range of initial void ratios and initial water contents along drying and wetting portions of the soil–water characteristic curve (SWCC). Wetting CBR tests were performed on the soil samples that were compacted and wetted to different dry densities and water contents. For drying tests, soil samples were prepared identically to the soil samples used in wetting tests, but after the compaction, they were desaturated by using the air-drying technique. The general trends observed are discussed and are compared in relation to some available data in the literature. Additionally, the experimental data appeared to show a distinction in the response of CBR along drying and wetting paths. The hysteretic detected response of CBR was discussed with relation to the hysteretic nature of the SWCC.