The current practice in the construction of jointed plain concrete pavements (JPCP) in India is to lay paving quality concrete (PQC) over roller compacted concrete designated as dry lean concrete (DLC). A plastic sheet of thickness 125 microns is placed as a bond-breaking layer at the interface of DLC and PQC. By placing the PQC layer directly over fresh lean concrete (LC), the two layers get bonded without any extra bond breaking layer and also there can be a considerable reduction in thickness of the PQC, Reducing the PQC layer thickness decreases the amount of aggregates used, helping in the preserving of quality aggregates which are rapidly depleting. Pavements, where the PQC is laid directly over LC, can be designated as a two lift concrete pavement. Joints have to be provided with deep saw cut to avoid random cracking. The LC can be made up of recycled concrete or marginal aggregates to obtain a sustainable pavement. However, readymade analytical solutions are not available for computation of stresses in two lift bonded concrete layers for pavement design. The paper presents a three-dimensional finite element solution for stresses in bonded concrete pavements. Stresses in both the layers are presented to arrive at an optimum thickness combination so that both the layers are safe during the design life. Stress computation is done for the conditions of simultaneous application of temperature gradients and axle loads. The cracking of LC layer due to high flexural stresses at the bottom is found to be the critical factor in the design of two-lift concrete pavement.
Contributors: Swarna, S. T., Reddy, M. A., & Pandey, B. B.