STRUCTURAL ANALYSIS OF COLD IN-PLACE RECYCLED ASPHALT MIXTURES, WITH ADDED GLASS FIBRE

The main purpose of this paper is to perform a structural analysis of cold in-place recycled asphalt mixtures, with added cement and foamed bitumen, as well as dispersed glass fibre waste. The employed methodology was carried out on specimens extracted from asphalt mixtures recycled in-place on two separate road sectors in Romania. The structural analysis of the recycled mixture was performed using both a stereo microscope and a scanning electron microscope. The study revealed both general and detailed bonding characteristics of the fibre-mixture interface, as well as glass fibre dispersion and coating deficiencies, which play a significant role in the behaviour of the recycled material. Laboratory tests have shown that a Gaussian-type of variation is obtained for the Marshall stability values, as the glass fibre waste content ranges between 1.5 % and 5.0 %. As asphalt mixtures reinforced with glass fibre have a complex microstructure, the filament dispersion factor and the bundle efficiency factor were studied. These factors are based on geometrical and bonding features of the recycled material with added glass fibre, describing the microscopic structure of the recycled asphalt mixture. The use of dispersed glass fibre waste to reinforce recycled asphalt mixtures improves the mechanical properties of road structures and delays the generation of micro-cracks in the recycled material, through their reinforcing function. Given the need to reduce the negative effects of glass fibre waste on the environment, as well as the production of asphalt, the dispersed reinforcement of recycled road structures presents technical, economic and environmental advantages.