Case study of construction quality control monitoring and strength evaluation of a lateritic pavement using the dynamic cone penetrometer

In this study, the quality and strength of unstabilized lateritic pavement layers of a 14 km single carriageway road under construction in Minna, Nigeria were measured and monitored by the Dynamic Cone Penetrometer (DCP) test in conjunction with standard laboratory testing of bulk and cored samples taken from designated sections. Atterberg’s limit tests revealed high liquid limits as well as plasticity index values at some sections in the sub-base layer. The dynamic cone penetrometer index (DCPI) values for the subgrade layer ranged from 3 mm/blow to 10 mm/blow whereas, DCPI values for the sub-base layer were observed to remain within a range of 5 mm/blow to 16 mm/blow. It was also found that good correlation similar to those developed by other researchers exists between CBR and DCPI values. However, comparison between the correlations by Transport Research Laboratory (TRL) and the one developed in this study showed that for both subgrade and sub-base layers, the new equation predicts slightly lower CBR than the TRL model. From the laboratory evaluation of soil samples, the subgrade CBR values ranged from 27 to 74% which qualify as good to excellent subgrade materials whereas the sub-base CBR varied from 15 to 50% and are rated as poor to good sub-base.