Retarding crack reflection using bitumen-rubber seals and overlays – historic overview of CSIR Research

Abstract

Crack reflection on roads with cemented layers is a significant problem world-wide and can lead to premature failure. Innovative road materials such as bitumen-rubbers possess the potential to successfully retard crack reflection, thereby minimizing damage to roads from water ingress. The research work conducted on bitumen-rubbers in conjunction with the knowledge generated on the retardation of crack reflection has led to several developments and innovations for the road industry. One such innovation is the development of the Crack Activity Meter (CAM), a device capable of measuring horizontal and vertical crack movements simultaneously. The CAM has been successfully used in conjunction with the Heavy Vehicle Simulator (HVS) during several accelerated pavement tests of road sections containing bitumen-rubber materials. Results from various laboratory investigations in conjunction with these field tests spans over decades of research into aspects such as crack movement monitoring, fatigue testing of bitumen-rubber asphalt and their performance under varying environmental and loading conditions. This paper provides a historic overview of the research conducted at the CSIR relating to the use of bitumen-rubber materials to successfully retard crack reflection. The paper additionally discusses the initial history, developments and early laboratory work conducted on the performance of bitumen-rubber materials in South Africa. Finally the paper identifies gaps in research in line with current day trends and developments that may be explored further for new methods of improving the successful retardation of crack reflection.