A Unique Pavement Rehabilitation Treatment for 6th Avenue SE Calgary - Concrete Overlay

摘要

Maintenance and rehabilitation strategies are critical components of a pavement management system. Effective rehabilitation improves the pavement performance and prolongs the service life of an existing pavement. Strategies for rehabilitation of flexible pavements in Calgary traditionally included mill and overlay or reconstruction. Less common is partial depth in-place recycling and full depth in-place recycling. While the selection of the optimal rehabilitation strategy can be straightforward when the distress is confined to the upper layers, much more complex and expensive repairs are required when the surface problems are related to structural deficiencies in the base or subgrade. Westbound 6th Avenue SE in Calgary between 3rd Street and Macleod Trail is a four-lane roadway (one-way direction) that experienced moderate severity transverse cracking, extreme rutting and ravelling. Most of the distress was noted in the right most bus lane and at the bus stop. A coring program to determine the pavement layer thickness and a FWD survey to determine the back-calculated modulus of the subgrade (Mr) formed the basis for the selection of a rehabilitation strategy. A bonded concrete overlay was selected as a cost-effective methodology while assuring an extended service life. Detailed materials and construction specifications were developed for the project. The initial construction was carried out in September 2010 and was not successful due to the contractor's inexperience. Investigation of the project indicated that the bond between the concrete overlay and asphalt surface was not achieved, the thickness of overlay varied, the concrete used was not suitable for the application and the control joints were not correctly installed. The re-construction commenced in May 2013 over a long weekend. Within 48 hours, the existing concrete overlay was removed, pre-overlay repairs were conducted, surfaces were cleaned to provide a good bond with concrete, and, the overlay was placed followed by curing compound application and control joints construction. Post-construction inspection indicated no major reflective cracking and a good quality surfacing for the bus lane. This rehabilitation project confirms that bonded concrete overlays provide an alternate solution to flexible pavement rehabilitation particularly for high volume heavy traffic sections with frequent stops and take-offs. The construction experience from this project also emphasized the need for well-defined specifications, experienced contractors and a quality management program during the pre-construction, construction and post-construction activities. This paper discusses all the above activities and the challenges with the construction in detail.