Determining the optimum amount of recycled asphalt pavement (RAP) in warm stone matrix asphalt using dynamic creep test

Abstract

This research is conducted to investigate the use of a laboratory experiment to evaluate the influence of changes in the percentage of recycled asphalt pavement (RAP) content on rutting resistance as measured by the flow number test achieved by three-stage model and the minimum rate of total permanent deformation. In this research, only one aggregate gradation with NMAS of 19 mm, one virgin binder (AC 60–70), and one RAP material source at six levels of content (0, 10, 20, 30, 40 and 50%) have been selected to prepare the stone matrix asphalt (SMA) mixtures. Furthermore, two warm mix asphalt additives including zycotherm and sasobit have been used in manufacturing (SMA) samples to carry out dynamic creep test in two levels of stress rate (300 kPa and 650 kpa), and Topcel additive fibers have been used to prevent draindown of these types of asphalt mixtures. Then, computerized programming has been developed to obtain regression coefficient parameters of the equations in three-stage models by Matlab software. Also, the correlations have been found between flow number achieved by the three-stage model and minimum rate of total permanent deformation. The result has indicated that there are good correlations between the two methods. Also, the results of the dynamic creep test to measure the flow number in 650 kPa stress level showed that by adding RAP to control SMA specimen, the FN content increases. Moreover by adding Zycotherm to samples manufactured by SMA specimen containing the RAP, the FN content increases by increasing RAP up to 40%. Also by adding sasobit to samples manufactured by SMA specimen containing the RAP and Zycotherm, the FN content increases by increasing RAP up to 30%. The highest amount of flow number (FN) relates to a specimen containing both zycotherm and sasobit and 30% RAP.