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Evaluation of Composite Pavement Unbonded Overlays: Phase III (TR-478, HR-1093, Proj. 2)

Scarified pavement with bars in place along edge

Stapled No. 4 bars that tie the widening unit to the thin overlay


Principal investigators:

Student researcher:

Project status


Start date: 09/25/01
End date: 08/31/06


Report: Evaluation of Composite Pavement Unbonded Overlays: Phase III (TR-478, HR-1093, Proj. 2) (2 mb pdf) August 2006

Tech transfer summary: Thin Unbonded Overlay Performance on Composite Pavement ( pdf) Aug 2006



About the research

Abstract: In recent years, thin whitetopping has evolved as a viable rehabilitation technique for deteriorated asphalt cement concrete (ACC) pavements. Numerous projects have been constructed and tested, allowing researchers to identify the important elements contributing to the projects? successes. These elements include surface preparation, overlay thickness, synthetic fiber reinforcement usage, joint spacing, and joint sealing. Although the main factors affecting thin whitetopping performance have been identified by previous research, questions still existed as to the optimum design incorporating these variables. The objective of this research is to investigate the interaction between these variables over time.

Laboratory testing and field testing were conducted to achieve the research objectives. Laboratory testing involved shear testing of the bond between the portland cement concrete (PCC) overlay and the ACC surface. Field testing involved falling weight deflectometer deflection responses, measurement of joint faulting and joint opening, and visual distress surveys on the 9.6-mile project. The project was located on Iowa Highway 13 extending north from the city of Manchester, Iowa, to Iowa Highway 3 in Delaware County. Variables investigated include ACC surface preparation, PCC thickness, slab size, synthetic fiber reinforcement usage, and joint spacing.

This report documents the planning, construction, and performance of each variable in the time period from summer 2002 through spring 2006. The project has performed well with only minor distress identification since its construction.