Experimental Analysis of Bond Strength between Bituminous Paving Layers in Laboratory Settings

The purpose of this research is to evaluate the bond strength between various combinations of bituminous layers in a laboratory setting. The bond between these layers is critical for the overall performance of pavement under traffic stresses. Bituminous tack coatings are widely used to improve interlayer adherence. This study examines two layer combinations: bituminous concrete (BC) on dense bituminous macadam (DBM) and semi-dense bituminous concrete (SDBC) on BM. A variety of tack coat materials are employed, including bitumen, Cationic Rapid Setting with low viscosity (CRS-1), and Cationic Medium Setting with high viscosity (CMS-2) emulsions. Bond strength is tested on cylindrical specimens at typical service temperatures (25°C, 30°C, 35°C, and 40°C) and various tack coat application rates. The testing procedure follows the standard Marshall Procedure, where the tack coat is applied, and the top layer is suitably covered in the same mould. The bond strength between layers is then evaluated using a specially designed attachment known as the "bond strength device," which is connected to the loading frame of the Modified Marshall Testing Apparatus. The results indicate that interlayer bond strength is influenced by test temperature, with a reduction observed as temperature increases. The type of tack coat and the specific layer combination also affect binding strength. The required amount of tack coat varies depending on the tack coat type and layer combination. Overall, this study provides insights into improving the bond between bituminous layers in pavements, thereby enhancing their performance and durability under traffic-induced stresses. Keywords: Interlayer bond strength, Tack coat, Bituminous layer combination, Bond strength device.