A pilot study of instrumented unbonded concrete overlay in Toronto

Unbonded concrete overlays provide structural rehabilitation and can be cost effective when the existing pavements are highly distressed and/or removal of existing pavement layers is not desirable. This paper describes a pilot study, which involves a three way partnership between the University of Waterloo, the Cement Association of Canada and the City of Toronto, to evaluate and document the performance of the first instrumented unbonded concrete overlay in Canada. The rehabilitation area is located at a heavily-trafficked intersection on Bloor Street and Aukland Road in the City of Toronto. The large volumes of bus traffic from the nearby subway station caused significant damage to the pavement structure. The rehabilitation design was composed of placing an unbonded concrete overlay on Bloor Street and replacing the section on Aukland Road with full depth exposed concrete. Twelve strain gauges are embedded in the concrete layer and they are strategically located along the wheel paths of the buses. The sensors are being monitored to assess long-term performance of the concrete overlay and the full depth concrete subjected to traffic and climatic loads. This paper outlines the design parameters, site conditions, and material properties of the overlay. The construction and full-scale instrumentation of this project are described, followed by preliminary analyses of up-to-date performance records.