Laboratory evaluation of SMA mixtures containing different additives

For many years, rutting in asphalt mixtures has been identified as one of the most critical types of distresses. To overcome this problem, Stone Matrix Asphalt (SMA) as a type of rut resistant asphalt mixture has emerged since 1970s. The use of different additives such as fibers or polymers seems to be essential in these mixtures to reduce the amount of binder drain down as the main problem of using this type of asphalt concrete. In this research, two types of additives such as Regular additives (styrene-butadiene-styrene and mineral fiber) and a Compound additive (Rheofalt® wkr-2) were used to improve the SMA mixture performance and decrease the binder drain down. Binder properties tests and mixture performance tests including Marshall test, Indirect Tensile Strength (ITS), moisture susceptibility and dynamic creep tests were performed to evaluate the performance properties of these mixtures. The results indicated that Rheofalt® wkr-2 had a positive effect on binder properties and SMA mixture performance. And as such, the effect of 10% of it was more considerable compared with other dosages. There was no need of using additional additive to reduce binder drain down when using Rheofalt® wkr-2 as a modifier. The effect of Rheofalt® wkr-2 was more than SBS and mineral fiber in terms of moisture sensitivity; however, SBS was more capable of improving Marshall and rutting properties of SMA mixtures than other additives. Based on the statistical analysis, it could be concluded that there are significant correlations between Marshall, indirect tensile strength and creep performance of SMA mixtures.© 2011 Asian Network for Scientific Information.