Reﬁning laboratory procedure for artiﬁcial RAP: A comparative study Benjamin F. Bowers, Baoshan Huang ⇑ , Xiang Shu Department of Civil and Environmental Engineering, University of Tennessee – Knoxville, 325 John D. Tickle Building, Knoxville, TN 37996, USA highlights  Different lab procedures of making artiﬁcial reclaimed asphalt pavement (RAP) are evaluated.  Staged extraction method is implemented to evaluate in binder layered system of artiﬁcial RAP.  FTIR was used to study staged extraction layers.  The uniformity of asphalt binder layers around artiﬁcial RAP was evaluated.  Optimum lab procedure of making artiﬁcial RAP was recommended. article info Article history: Received 12 July 2013 Received in revised form 6 October 2013 Accepted 2 November 2013 Available online 8 December 2013 Keywords: Artiﬁcial RAP Laboratory aged RAP Reclaimed asphalt pavement Fourier Transform Infrared Spectroscopy FTIR Staged extraction abstract Laboratory aged, ‘‘Artiﬁcial RAP’’ is often used in controlled experiments in order to simulate the perfor- mance of paving mixtures containing RAP. Many different methods have been used to generate artiﬁcial RAP and they often modify the American Association of State Highway and Transportation Ofﬁcials (AASHTO) R30 speciﬁcation for oven aging gyratory compaction cylinders. Two modiﬁed AASHTO R30 methods were evaluated at 85 °C and 115 °C, as well as an artiﬁcial RAP created using PAV aged asphalt that had undergone one or two PAV cycles at 100 °C and short term aging. A staged extraction procedure using trichloroethylene solvent was used to evaluate a four layered binder system around the aggregate. Each layer was studied with Fourier Transform Infrared Spectroscopy (FTIR) and an aging index is com- puted for comparison. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The use of reclaimed asphalt pavement (RAP) in pavement mix- tures is of high priority to the asphalt paving industry due to its many sustainable and economic implications. Research is often conducted in a laboratory setting to evaluate the effectiveness of RAP within the pavement mixture. There are many factors that play into the performance of the RAP within the mixture that are being studied in controlled settings. Some fundamental research requires extremely sensitive testing techniques such as Fourier Transform Infrared Spectroscopy (FTIR), while others rely heavily on traditional macro-performance testing such as tensile strength ratio (TSR) or outputs of the Asphalt Mixture Performance Tester (AMPT). Though the scope of applicable tests for RAP in new mix- tures is large, there is often a need for a controlled RAP to evaluate the test results. Much of the RAP milled from roads around the United States and worldwide is of an unknown origin. This may pose a problem in some controlled experimental designs because of the potential variability of the RAP binder when removed from the stockpile which may lead to differences in performance. Thus, in some cases it is necessary to create an ‘‘artiﬁcial RAP’’, or a RAP with known properties, using traditional laboratory aging techniques. Many credible research studies have relied on artiﬁcial RAP, sometimes alternatively named ‘‘laboratory produced RAP’’, as a controlled variable within the study. However many of these studies rely on different methods of creating the artiﬁcial RAP. In general, a mod- iﬁcation of AASHTO R30 ‘‘Standard Practice for Mixture Condition- ing of Hot Mix Asphalt’’ is used where the long term aging process is performed on a loose mixture rather than a compacted specimen is common. The objective of this research paper is to use a sensitive chemical testing technique, FTIR, to evaluate the current practice of artiﬁcial RAP creation along with a secondary methodology which relies primarily on the traditional binder aging techniques of the Rolling Thin Film Oven (RTFO) and the Pressure Aging Vessel 0950-0618/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2013.11.003 ⇑ Corresponding author. Address: Department of Civil and Environmental Engi- neering, University of Tennessee - Knoxville, 325 John D. Tickle Building, Knoxville, TN 37996, USA. Tel.: +1 (865) 974 7713; fax: +1 (865) 974 2669. E-mail addresses: bbowers4@utk.edu (B.F. Bowers), bhuang@utk.edu (B. Huang), xshu@utk.edu (X. Shu). Construction and Building Materials 52 (2014) 385–390 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat