Structural Performance of Ultra-Thin Whitetopping on Illinois Roadways and Parking Lots
A performance evaluation of ultra-thin whitetopping (UTW) pavements in Illinois was undertaken in 2012–2014 to evaluate current design procedures and to determine design life criteria for future projects. The two main components of this evaluation were (1) visual distress surveys of 20 existing UTW projects across the state to document and quantify distresses and (2) falling weight deflectometer (FWD) testing of eight of these UTW projects to evaluate structural performance.
The findings of the surveys are detailed in this report. Deflection data collected during FWD testing were used to directly calculate load transfer efficiency and assess joint performance, but there was no existing method to assess the in situ structural properties of UTW pavements. To better characterize structural performance, a backcalculation procedure for UTW pavements was derived and applied to the deflection data obtained from FWD testing. The backcalculated effective concrete thickness quantifies the load carrying capacity of the UTW pavement, variation of the structural capacity as a function of distance along the roadway, and potentially the condition of the concrete–asphalt bond interface and the underlying asphalt concrete layer.
The findings of the visual distress surveys and the FWD data analysis largely agreed with each other and were studied to help provide a greater understanding of factors that affect UTW performance. From this analysis, a number of conclusions and recommendations were made regarding UTW pavement design and construction.
Authors: Daniel King and Jeffery Roesler