Paper and Presentation by John Figueroa and Jennifer Kemp from ASCP 4th Concrete Pavements Conference 2017
This paper describes the unbonded concrete overlay design option prepared for the rehabilitation of the Marulan bypass plain concrete pavement. The unbonded concrete overlay thickness design is based on the application of the fracture mechanics model developed by the University of Minnesota.
The Marulan bypass pavement is part of the Hume Highway between Sydney and Melbourne and it was constructed in 1987. It consists of 7 km of dual carriageway highway in both the southbound and northbound directions and each direction carries around 3,000 heavy vehicles per day. The existing pavement is failing at a rate of 2-3% per year and does not have the structural capacity to sustain future growth of heavy vehicle traffic and increasing axle masses for the route.
The pavement design method used in this concept design is an improvement of the current Austroads procedure which is not capable of quantifying the loads required to initiate and propagate reflective cracks in concrete pavements. The model determines the load capacity of a new pavement designed to the current Austroads thickness design procedure, and then determines the thickness and material properties for the unbonded concrete overlay that will yield the same load capacity.
The overlay thickness analysis suggests that increasing the thickness of the asphalt interlayer and increasing the strength of the concrete overlay are effective ways of improving the load-carrying capacity of the pavement. The design outcome is a relatively thin precast concrete solution that is capable to resist reflective cracking.
Precast concrete slabs can be produced under environmentally controlled conditions, which can result in pavements with improved durability, better engineering properties and thinner solutions.