Pavement Evaluation and Rehabilitation Design Methodology Currently Used on Low-Volume Roads in Southern Africa

A pavement evaluation and rehabilitation design methodology is currently employed in southern Africa on relatively light pavement structures used for low-volume roads. The pavements normally consist of natural gravel materials in most layers and thin bituminous surfacings. When nearing the end of their design lives, they exhibit distresses ranging from minor deformation through aging of the surface to structural cracking and potholes. Rehabilitation options normally involve light stone seals or other inexpensive and cost-effective treatments. The phases of investigation for pavement evaluation and rehabilitation designs start with desk study to establish the history of the road and its past performance from pavement management system outputs. Detailed visual evaluations are then conducted of road features and extent of various forms of distress. These data are presented followed by a decision-making process to select areas for more detailed testing. All the information is used to determine the causes of distress and likely rehabilitation alternatives. Further destructive and nondestructive testing is carried out to predict performance of rehabilitation designs and equivalent annual cost comparisons. Rehabilitation design is also done with use of the dynamic cone penetrometer. Decision criteria are set for use of tests undertaken in the assessments, and test results are evaluated. This procedure normally results in a wide range of rehabilitation options, from application of a diluted emulsion as a surface rejuvenator to more extensive patching and resealing to major rehabilitation and overlays. This process effectively produces cost-effective solutions that maximize limited budgets. It is essential that the road authority be prepared to share the risks of the low-cost options with the designer. In this way benefits of low-cost solutions are realized, whereas, in a limited number of instances, premature distress may have to be repaired under routine maintenance.