The following recommendations are based on the chapter III of a State of the Art review conducted by the Task Group 2 of the RILEM Technical Committee 241-MCD ''Mechanisms of cracking and debonding in asphalt and composite pavements'' (Petit et al in Mechanisms of cracking and debonding in asphalt and composite pavements. Chapter III of the State-of-the-Art report of the RILEM technical committee 241-MCD series, vol 28. Springer, New York, pp 103-154. ISBN 978-3-319-76848-9 2018). The recommendations mostly concern "pure" fracture mode test methods that are currently used worldwide and even standardized, while mixed mode test methods developed by few research teams have not received full attention. This paper intends to give guidance for the application and characterization of interlayer bond testing, looking at the appropriate test methods and the importance of influencing parameters.

No abstract

No abstract

An effective and durable bond between the various constituent layers is an absolute prerequisite for the durability of a road pavement. To ensure the adhesion between successive road construction layers, cationic bitumen emulsions are the most frequently used type of tack coats. Several tests are currently available to evaluate the bonding performance between layers based on different loading modes (shear, torque and tensile) They vary in regard of test devices, test temperature, loading mode as well as sample geometry and preparation and hence they lead to different results. In this context, the European standardisation committee CEN TC227/WG1/TG2 "Test methods for bituminous mixtures" has developed a prestandard prEN12697-48 "Bituminous mixtures-Test methods for hot mix asphalt-Part 48: Interlayer Bonding" for the determination of interlayer bond strength where three main normative test methods are considered: tensile adhesion test (TAT), shear bond test (SBT), torque bond test (TBT). A site test method to evaluate the tensile bond strength making use of a practical clamping device and used for many years in Quebec, called layer adhesion measuring instrument (LAMI), was recently included in the prestandard. This article gives an overview of the different methods and discusses the results of a study in the laboratory (SBT, TAT) and on site (LAMI) in which these pre-normative interlayer adhesion tests were used. The study leads to recommendations for the methods described in prEN 12697-48 and shows the differences between the methods. The ultimate aim of this study is to come to recommendations for improving the adhesion performance of multilayer pavements and to propose values for minimum interlayer bond strength to be achieved on site.

No abstract