The investigation of the effect of polypropylene fiber addition tothe static creep behaviour of bituminous mixtures

The heavy vehicles in the composition of traffic, non-foresightable axle loads and tire pressures have motivated the highway engineers to search for new pursuits. In addition to these repetitive heavy traffic loads, the great fluctuations in the climate conditions and non-counteraction of the mixture properties to the existing necessities, permanent deformations started to occur in the superstructure. Especially in our country, the addition of the overloaded vehicles into traffic stream and the occurrence of rutting, because of the hot climatic conditions, has become one of the most predominant distress parameters. Because of the above mentioned reasons, the modification of physical and chemical properties of the bituminous binders has been assimilated to ensure the desirable performance in the flexible pavements.Polypropylene (PP) is completely a native modifier and it does not have any dependence to abroad in case of technology. When viewed from this point, the modification of bituminous binders with PP is a very important step for our country?s ?economical? concerns. In this study, first of all, the physical and chemical effects of PP on bitumen were investigated. Next, the amount of ?optimum? PP that has to be added into mixture was determined. In order to determine it, first, static creep tests and Marshall tests were carried out; images of the PP added bituminous binder under fluorescence microscopy was researched. With the application of physical and mechanical tests to the Marshall specimens prepared with the optimum PP amount that was obtained at the end of these three tests, optimum bitumen content was determined and finally economical analyses were carried out. After examining the obtained results, it has been found out that the PP modification of bituminous binders has developed the physical and mechanical properties of the mixture and substantially improved the resistance to permanent deformations. Besides, the PP modification results in 30 % economy form bitumen which is very important for the costly asphalt concrete production in recent times.