Common surface defects in asphalt road pavements and unexpected causes

Correct interpretation of the cause or causes of defects and deterioration of road pavements is important for the selection of the most appropriate maintenance or repair strategies and for the design of new pavements. However, identifying the cause of pavement defects is not as simple as merely looking for aspects of specifications that have not been fully met. The cause of failures is often attributed to a number of factors, one of which, if absent, would not necessarily result in any defects. This paper describes and analyses three case studies where three different mechanisms have caused the deterioration of both asphalt concrete and double chip sealed surfacings. The first mechanism is the peculiar formation of potholes below certain structures and trees, which can result in large-scale ravelling and potholing on certain road categories. The second mechanism is an unusual cause of the flushing of bitumen on both types of surfacing. The third mechanism results in the formation of potholes at roundabouts in tropical countries. The paper concludes by recommending the appropriate maintenance measures for the cause of each defect and appropriate designs to minimise the likelihood of their occurrence.