Design procedure for thin fiber reinforced concrete overlay on asphalt pavement

The use of thin synthetic fiber reinforced concrete (SFRC) overlay for resurfacing deteriorated asphalt pavements started in early 1990's and has seen rapid growth in recent years. It involves placing very thin concrete slabs (50 to 100 mm thick) on old asphalt pavement to form bonded (or partially bonded) composite pavements and has been generally referred to as ultra-thin whitetopping (UTW). The reduction of thickness is justified by the use of high quality concrete with relatively high strength, shorter joint spacing and bond between the concrete and existing asphalt pavement. Under the sponsorship of the Portland Cement Association (PCA), this paper presents the development of a mechanistic design procedure for UTW pavements, which included extensive field load testing and theoretical analysis of UTW behavior using finite element models. In this design procedure, two types of pavement failure were considered, portland cement concrete fatigue under corner loading and asphalt concrete fatigue under joint loading. Temperature induced stresses and strains were also included in the design. The design procedure is viewed as the first generation design method. It will be refined as more field data (especially long-term performance data) become available.