IFB 19-112 NM - DTD - Research Study on Bond Strength in Concrete Overlays of Asphalt

Background – Successful thin concrete overlays of asphalt pavement rely heavily on the bond between the concrete and asphalt layers. Stresses and strains at the bottom of the concrete layer increase with the loss of bond that may cause premature failure of the concrete overlay. The current CDOT model assumes a 10 percent loss in bond strength due to a partial bonding condition. Based on this assumption, the tensile stress in the bottom of the concrete layer was determined to be fifty one (51) percent higher than that of a fully bonded slab system. The strain transfer from the concrete slab to the asphalt layer due to the actual bond strength should be evaluated to validate our current model.
This study has the following objectives: 1) evaluate the loss of bonding strength in thin (4 to 7 inches) concrete overlays of asphalt; 2) evaluate the stress transfer in the bottom of concrete overlays of asphalt; 3)            validate current CDOT white topping models to analyze the effect of bond interface on load induced concrete stresses; and 4) evaluate the need to refine CDOT white topping pavement design model for bonded concrete over asphalt based on field performance data.
It is expected that the results of this study will lead to the successful revision of CDOT’s bonded concrete overlay of asphalt design procedures to provide a higher level of confidence when considering this rehabilitation technique and to reduce the required thickness of the overlay as appropriate.  CDOT is seeking the insights of proposers on how best to achieve the objectives of the research. The proposal shall describe a research effort that can be accomplished realistically within the constraints of available funds and contract time and shall include a breakdown of all costs on a task-by-task basis.