Recommendation of RILEM TC 280-CBE: test method to assess the bonding of microsurfacing mixtures using the shear bond testing (SBT) apparatus

Microsurfacings are widely recognized as a valid solution for reducing the consumption of energy and raw materials in the construction and maintenance of road surfaces. They require specifically formulated mixtures, designed to compensate for the variability of the substrate and to ensure a durable bond at the interface of the newly applied layer. In fact, the surface texture of the support has a strong effect on the bonding behaviour, as it influences the interlocking and adhesion at the interface. Insufficient interlayer bonding can lead to slippage and to partial or complete delamination of layers. This can impair the functionality of the pavement, as large cracks and potholes can occur. Although several methods for assessing the mechanical performance of microsurfacings are included in the main international standards, there is a lack of standardised guidelines for assessing their bond strength. This recommendation proposes a testing procedure to assess the interlayer bond strength of microsurfacing mixtures using a common shear testing device. In addition to the results of the shear strength, the surface of the substrate can be characterised with regard to its texture using a simple laboratory method.