Deflections of Lateritic Gravel and Stone Base Pavements of low volume Tea roads in Kenya.

Abstract

Results are described from a testing program of a tea road on the slopes of the Aberdares where tea is the main cash crop. The 5.5-m-wide low-volume road has been carrying the equivalent of about 7,000 standard axles per year. Two experimental sections were identified on the road, one of which contained a lateritic gravel base and the other a stone base. The experimental sections were subjected to a detailed pavement condition survey to identify types and extent of distress features such as potholes, crazing, and edge failure after more than 10 years of service. In situ field tests were carried out on the subgrade, subbase, and base materials to determine in situ field density and moisture. The dynamic cone penetrometer and Clegg impact hammer were used to establish the in situ California Bearing Ratio (CBR) values. In addition, pavement deflections and radius of deflected profile were measured using the Benkleman deflection beam. The results of the studies indicate that the experimental sections are still performing well after about 16 years of service. The deflection values obtained were below 1 mm, and the radius of curvature of the deflected profile was greater than 150 m. The pavement condition surveys tended to show that stone-based sections (standard construction) were marginally more distressed than the lateritic gravel-based sections (substandard construction). The study indicates that low-volume roads can be constructed using substandard materials such as lateritic gravels, for which the cost of the road is about two-thirds that of conventional road materials that meet specifications.