Mechanistic Modeling of Unbonded Concrete Overlays
Principal Investigator:
Roberto Ballarini, Professor, Civil Engineering
Project Summary:
An unbonded concrete overlay (UBCO) is a portland cement concrete (PCC) pavement slab that is separated from an existing PCC slab by a separation layer, which is usually a thin layer of asphalt concrete. UBCOs have been used since 1916 to rehabilitate PCC pavements, and the design of UBCOs for highway projects has always mirrored the design of UBCOs for aircraft pavements. This practice results in a very conservative design for UBCO in highway applications and prevents UBCO from being a more cost-effective rehabilitation solution. Among existing UBCO designs is the procedure developed by the Minnesota Department of Transportation (Mn/DOT). The goal of this research is to develop mechanistic models for cracking in the existing PCC of an UBCO and to review existing UBCO designs in order to 1) better understand rehabilitated pavement systems that use UBCO and 2) better design the properties (thickness, composition) of a planned UBCO. Both of these improvements would provide Mn/DOT with a rational basis for revising its UBCO procedures. As it stands, UBCO constructed by Mn/DOT may be excessively thick (typically around 11 inches) given the exceptional quality of Mn/DOT PCC and the nature of the application (highways, not airfields). This research may allow Mn/DOT the opportunity to "thin up" its UBCO design and thereby reduce construction costs.
Sponsor:
Project Details:
- Start date: 06/2009
- Project Status: Active
- Research Area: Infrastructure
- Topics: None