Investigating the effect of AC overlays, reinforced with Geogrid and modified by sasobit on rehabilitation of Reflective cracking

In this paper, it has been attempted to evaluate the performance of asphalt overlays which were reinforced with geogrid, modified by sasobit and combination of them on rehabilitation of reflective cracking. The laboratory tests under dynamic loading in bending mode were conducted to investigate reflective cracking retardation compared to reference samples. The results illustrated that in a certain range of variables, temperature variations and sasobit percentages are the most effective parameters for fatigue life and other responses. The other effective variable was the type of interlayer in asphalt slabs. Furthermore, it has been found that the combination samples (modified by sasobit ,reinforced with geogrid and a 3cm sand asphalt layer) (1SP.G.SA & 2SP.G.SA) had a better performance such as improving fatigue life and reducing crack propagation in all loading and temperature conditions compared to reference samples. Based on the image processing results, it has been determined that the process and shape of crack growth, varies greatly in different temperatures. Generally, at low temperatures (20 °C) and frequencies the cracks grow from bottom to top and the width of them get smaller. However, with increase the temperature and loading frequency the top down cracks are also observed, due to the reduced resistance of the asphalt resulting from the reduction of adhesion and the fastening between the aggregate and bitumen.