Performance Evaluation of a Trunk-A Road in North Central Nigeria

Pavement maintenance and rehabilitation have been neglected in Nigeria for a very long time and has resulted to maintenance backlog. Design agencies in Nigeria still use California Bearing Ratio (CBR), even though the method is outdated. An introduction of Dynamic Cone Penetration Test (DCPT) was pertinent, even though the method is relatively old in some developed countries, it has not gain much prominence in Nigeria. A flexible pavement, constructed from Bida to Mokwa,, Nigeria, was Rehabilitated after 22 years of construction. This was done by placement of stone base course in one section and lateritic base course in the other. The stretch of the road was then overlaid with asphalt surfacing. Before commencement of the rehabilitation, DCPT tests were conducted on the road to evaluate performance of the pavement base and subgrade. Two years after the rehabilitation, an evaluation was carried out at five selected positions (two at crushed stone base and three at lateritic base) to evaluate the performance of the two base courses. The evaluation was carried out by coring the asphalt concrete and DCPT test below the hole created by corer to indirectly estimate the in-situ CBR of the base and subgrade courses. The results from both the stone base and lateritic base sections satisfy the minimum specifications based on standard. The study also showed that pavement failure along the road is not as a result of the materials used in the base course, but as a result of the excessive axle loads experienced by the road.