| Experimental measurements and numerical analyses were performed to investigate the early age behavior of bonded concrete overlays. Drying shrinkage, relative humidity, and thermal changes inside the overlay concrete were measured to define shrinkage and thermal gradients. Tensile bond strength was measured by a modified split tensile test and used for failure criterion in numerical modeling. Physical laboratory tests were performed to measure crack-mouth opening displacements (CMOD) and debonding length (DL) in bonded overlays. Swelling in substrate concrete was observed and found to be dependent upon w/c ratio.; Numerical analysis and classical elasticity analysis were performed to evaluate the stress distribution and strain field. A two-dimensional finite element was used to compute CMOD and DL, and results were in agreement with physical experimental measurements. From the analysis, it was found that greater overlay thickness increases stress at the top surface and interface of the overlay. A three-dimensional finite element analysis and physical laboratory measurement showed that debonding initiates at the corner of the interface and propagates into the inside and the middle of the interface. The classical elasticity solution confirmed the importance of substrate restraint. The results of this study provide recommendations for field practice.; A design guide was developed to predict cracking tendency in bonded concrete overlay at early age. The design guide, implemented as an EXCEL spreadsheet, is a practical tool for pavement engineers. The design guide calculates surface stresses and interfacial debonding stress due to shrinkage and thermal changes at early age. An engineer can use the design guide to study the interaction of material properties, environmental conditions, structural restraints, and overlay geometry. |
