The Effect of Polypropylene Modification on Marshall Stability and Flow

ABSTRACT: Asphalt concrete pavements because of their low initial cost are being preferred over portland cement concrete pavements. This advantage can be minimized if the mix design is not suitable for the road class and traffic composition. In North Cyprus use of unmodified asphalt cement in mix design causes unnecessary road maintenance on road section where traffic volume is high. In addition to extra cost of these repairs, the traffic disruptions also take place. The main surface distress types which cause these maintenance and disruption are rutting and fatigue cracking. For solving these problems different studies have been carried out, ranged from changing gradation to adding polymers and fibers to asphalt mixture. In this study, polypropylene additive was selected as fiber additive because of low-cost situation and having good correlation with asphalt pavement according to various studies. Two type of polypropylene (PP) additive in length (6 & 12 mm) were selected, 6mm long PP was used at three different percentages (0.1%, 0.2%, and 0.3%) in asphalt concrete mixture with 3.5, 4.0, 4.5, 5.0 and 5.5% percent of asphalt by weight of total mix. 0.5% of 6 mm long PP and 0.3, 0.5% of 12 mm long PP were added to optimum percent of asphalt, to see the difference in asphalt characteristics. Asphalt specimens were made by Superpave Gyratory Compactor (SGC), and analyzed by both Marshall Analysis and Superpave Analysis and finally tested by Marshall Stability apparatus. Adding polypropylene increased Marshall Stability (26%), and decreased Flow (38%). This increase in the percentage of air void is important for hot regions where bleeding and flushing are common. Keywords: Polypropylene fibers, Rutting, Marshall Stability and Flow. ……………………………………………………………………………………………………………………………………………………………………………………………………………………