The Influence of Mixing Conditions on the Macro-Scale Homogeneity of Asphalt Mixtures Blended with Reclaimed Asphalt Pavement (RAP)

Abstract

The homogeneity of asphalt mixtures blended with reclaimed asphalt pavement (RAP) is affected by many factors. Due to the complicated compositions of recycled asphalt mixtures, the inhomogeneity issue might cause insufficient mechanical properties of asphalt mixtures, even though a design method was appropriately adopted. Therefore, it is of great significance to study the influence of mixing conditions on the homogeneity of asphalt mixtures blended with RAP materials. This study focused on the macro-scale homogeneity of produced asphalt mixtures. Specifically, asphalt mixtures incorporated with 40% RAP content were produced in a laboratory using different mixing times and mixing temperatures. A multi-direction indirect tensile stiffness modulus (ITSM) test was proposed to quantify the homogeneity of produced samples. In addition, the digital image processing (DIP) method was used to identify the distribution of aggregates and RAP binder. The results indicated that the influence of mixing time on the macro-homogeneity of asphalt mixtures indicated that a longer mixing time was favorable for the material dispersion. The influence of mixing temperature mainly rested on two perspectives. One was that the temperature variation induced the change of binder viscosity. The other was that the temperature influences the diffusion process between RAP binder and new bitumen, which further affected the mechanical performance of produced asphalt mixtures.

An Analysis of Reclaimed Asphalt Pavement from a Single Source—Case Study: A Secondary Road in Romania

“…These aspects are analyzed individually in other scientific papers, while this study presents a comprehensive analysis of all above-mentioned aspects, which is a particularity of the applied methodology. RAP material performances are highlighted in previous researches/studies for both types of origin source, namely unique source or single project site [1][2][3][4][5], as well as multiple sources or project sites [6][7][8][9][10][11][12] collected using milling or other techniques or produced in laboratory after applying long-term aging techniques [13]. Thus, RAP obtained from unique or multiple sources presents significant inhomogeneity and is prepared with pre-processing techniques such as screening, sieving, crushing, storing separately according to its gradation stockpiles [14,15], or even mixing and storing in hybrid RAP stockpiles [16] suitable for further use in a new asphalt mixture.…”

Effect of Fractured Aggregate Particles on Linear Stress Ratio of Aggregate and Resilience Properties of Asphalt Mixes—A Way Forward for Sustainable Pavements

“…MR is considerably affected by the loading type, loading time (vehicle speed) and mix type [49,50]. MR of asphalt mixes was significantly improved by using coarse aggregates with more irregular morphologies at 25 • C [51]. Good correlation between MR and the maximum aggregate size can be observed when aggregates having maximum size of 3/8, 1/2, 3/4, 1 and 1.5 inches are used [52].…”