The aim of this investigation was to analyze the adherence between two layers of bituminous mixture when a geosynthetic material is placed between them. A new monotonic test procedure was developed that enables the evaluation of the influence of the binder type and content, and the typology of the geosynthetic material used. The validity of the procedure was demonstrated using dynamic tests. The results confirmed that highest adherence between layers is obtained through geogrids, with optimal residual binder content of 0.30 kg/m(2). In contrast, the tests with geotextiles were found to be less sensitive to binder content, with lower shear resistance for higher contents of binder. (C) 2009 Elsevier Ltd. All rights reserved.