Investigation of the bonding properties of bitumen using a novel modified binder bond strength test

The binder bond strength (BBS) test can directly quantify the bonding of bitumen-stone joints. However, the index "bond strength" used in this method cannot provide a clear distinction when evaluating the performance of various bitumen, and some results do not correspond to the field feedback related to the bonding performance. This study introduces a novel modified BBS test using the universal testing machine (UTM). The results of the standard BBS test and the BBS-UTM test on six unmodified bitumens and a styrene-butadiene-styrene modified bitumen (SBSMB) are compared, with the Cantabro loss test to validate the accuracy of the BBS-UTM test. The results show that the "bond energy" can be considered the critical indicator for characterising the bonding performance of different binders. The force-displacement curve in the BBS-UTM test is analysed and provides a mechanistic explanation for the mechanical response of bitumen during pull-off. The four-component test is conducted to link the bitumen composition characteristics to its bonding performance. It is found that bitumen adhesion is correlated to the content of asphaltenes. A higher saturates content shows more contribution of tenacity in the total bond energy, and an excessively high ratio of asphaltenes to resins may result in low bond energy.