A New Laboratory Test to Evaluate the Shear Resistance at the Interface of Thin Bonded Overlays

The effectiveness of thin bonded overlays depends upon the adhesion level at the interface with the existing concrete pavement. It appears that shrinkage, particularly at the very early ages (18-24 hours), is mainly responsible for delamination, i.e. separation between old pavement and overlay. The present paper discusses the results of a large number of laboratory tests performed within the ASTRA (Ancona Shear Testing Research and Analysis) program to: define a test to evaluate the interface shear resistance of thin bonded overlays in absence of normal stresses, thus simulating more closely the stress conditions caused by shrinkage; evaluate the role played by some parameters, such as primer type, curing time, surface roughness of the supporting concrete pavement on the interface shear strength.