A comparative study on the laboratory and field CBR values of granular sub-base material for pavement construction

California Bearing Ratio (CBR) test is a measurement of resistance to penetration for evaluating the strength of material used in the subgrade, subbase and base layers. In the present investigation, CBR of granular subbase materials (GSB) were tested for pavement evaluation during construction at Bagjola Bridge approaches near Rajarhat, New Town under Housing Directorate, Government of West Bengal. In this study, laboratory CBR was performed on Jhama metal and stone aggregate material collected from Salt Lake and airport end sites, respectively. Besides, field CBR test as per IS:2720 (Part 31) and dynamic cone penetration tests were performed on same material bed at both ends. In this paper, comparison between CBR values, i.e., field and laboratory under different conditions, including density and moisture content, were investigated.