Load Transfer and Joint performance in Whitetopping Pavements

Concrete Overlay

Abstract

Whitetopping is an effective means of extending the service life of bituminous pavements which are in need of rehabilitation. Concrete overlays are placed over deteriorated bituminous pavements with lesser thicknesses in the range of 100 to 200 mm. Joints are formed by saw-cutting the slab upto 1/3^rd the depth and cracks are developed below it to form aggregate interlocked joints. Thus, the load is transferred through the interlocking action of the aggregate particles across these cracks. This paper investigates the performance of these aggregate interlocked joints in Whitetopping due to the effects of various parameters. A three-dimensional finite element model of whitetopping has been developed for this purpose and the influence of several parameters on load transfer is investigated. Results indicate that load transfer efficiency of joint increases with increase in overlay thickness. However, the effect of the stiffness of existing bituminous layer on load transfer is more prominent for thinner concrete overlay due to the composite action. In case of different interface conditions, it is found that for lower overlay thickness, the stiffness contribution of bituminous layer is higher for bonded interface condition than for an unbonded one. Joint width and joint roughness significantly influence the load transfer behaviour. A narrow and rough joint increases considerably the load transfer efficiency and the performance of joint. Finally, an equation has been proposed to estimate the load transfer efficiency of aggregate interlocked joints considering various infleuencing factors.