Effect of rejuvenating agents on stone matrix asphalt mixtures incorporating RAP

Abstract

Economic and environmental considerations have encouraged the incorporation of Reclaimed Asphalt Pavement (RAP) in the new asphalt mixtures. The Stone Mastic Asphalt (SMA) mixture is a gap-graded mixture, which performs better than the conventional dense-graded mixtures. To incorporate RAP into SMA mixtures certain setbacks are to be mitigated. RAP consists of aged binder, which is aged due to oxidation. Because of ageing process, this binder will have a higher stiffness than that of the virgin binder. A rejuvenator is included to decrease the stiffness and that permits high RAP content. In this study, Waste Engine Oil (WEO) and Waste Grease (WG) are used as rejuvenators. The RAP content is varied at four levels (10, 20, 30 and 40% by weight of the aggregate) and at each level rejuvenator’s dosage is varied at 0, 3, 6 and 9% (by weight of the asphalt). Overall, 29 SMA mixture combinations are considered and laboratory-scale performances are studied. The statistical analysis such as three-way Analysis of Variance (ANOVA) test and main effect plot are performed to evaluate the significance of the three independent variables (i.e. RAP content, rejuvenator type and dosages) on the response variables (i.e. optimum binder content, Marshall quotient, retained Marshall stability and tensile strength ratio). From the results, it is concluded that 40% RAP content SMA mixtures can be produced without compromising the stone-on-stone contact, volumetric properties and moisture resistance. The statistical analysis points out that the WEO performed better than the WG. Overall, it is determined that 30% RAP with 6% WEO is superior SMA mixture with better performance.