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APPENDIX B: EXTRACTION AND recommended to use n-Propyl bromide due to its short RECOVERY PROCEDURES AT TFHRC shelf life and there may be product-specific prob- ASPHALT LABORATORIES lems with polymer modified asphalts and polyphos- phoric acid (PPA) modified asphalts. TCE with 15% There are three standard methods related to extrac- ethanol has been shown to be a superior solvent for tion and recovery of asphalt binders from asphalt removing most of the asphalt binder from aggregate1; mixtures: however, this is not so much a concern as is the con- 1. AASHTO T 164-06/ASTM D2172-01, cern for maintaining the bulk binder properties. Standard Method of Test for Quantitative Extraction Unfortunately, the effects of TCE on the chemistry of Asphalt Binder from Hot-Mix Asphalt (HMA) of the recovered binder are not understood. Further, 2. ASTM D 5404-97, Standard Practice for it has been shown that TCE solvent produces higher Recovery of Asphalt from Solution using the Rotary (i.e., stiffer)3 and hardened2 recovered binders. Evaporator Finally, TCE and related solvents were phased out 3. AASHTO T 319-03, Standard Method of for environmental reasons.3 Test for Quantitative Extraction and Recovery of Due to the nature of research, other solvents Asphalt Binder from Asphalt Mixtures may be used on a case-by-case basis for specialized extractions. For example, tetrahydrofuran (THF) may For extraction and recovery of asphalt binders, a be necessary for use with some polymer-modified combination of AASHTO T 164 and ASTM D 5404 binders or rubber-modified binders. THF should or AASHTO T 319 may be used. In AASHTO T 164, not be used on a regular basis (i.e., substituted for centrifuge extraction (Method A) is preferred to the toluene) and must be used with care due to its high reflux (Method B) because it minimizes heat hard- flammability. PPA-modified asphalt binders should ening of the asphalt binder. For routine extraction be extracted by other solvents (other than lab-grade and recovery of asphalt binders, it is recom- TCE and n-Propyl bromide, toluene, toluene/ethanol, mended to use AASHTO T 319 since this method and THF) that do not contain stabilizers that react was designed to minimize solvent hardening of the with the acid in the binder.4 binder, provide complete removal of the solvent, and more completely extract the asphalt binder from the aggregate. Several different solvents may be used such as n-Propyl bromide; trichloroethylene 1Cipione, C.A., R.R. Davison, B.L. Burr, C.J. Glover, and J.A. (TCE), reagent grade; or toluene, reagent grade. There Bullin. Evaluation of Solvents for Extraction of Residual is large variability associated with determining recov- Asphalt from Aggregates. Transportation Research Record: ered binder properties; however, the type of solvent Journal of the Transportation Research Board, No. 1323, used between TCE, toluene, and n-Propyl bromide Transportation Research Board of the National Academies, does not produce statistically significant differences Washington, D.C., 1991, pp. 4752. 2Abu-Elgheit, M.A., M.J. Ijam. Change in Consistency and in the results for Superpave Binder Tests. Composition of Trichloroethylene- and Trichloroethane-Treated For routine extraction and recovery of asphalt Asphalts (Annotation). Talanta, Vol. 29, pp. 11314, 1982. binders, Turner Fairbank laboratories will use 3Stroup-Gardiner, M., J.W. Nelson. Use of Normal Propyl Bro- toluene, reagent grade, as the solvent and, accord- mide Solvents for Extraction and Recovery of Asphalt Cements. ing to AASHTO T 319, after the third wash NCAT Report 00-06, November 2000. toluene, reagent grade, combined with ethanol, 4Important Note When Recovering Binders Containing PPA. absolute, in proportions of 85% toluene and 15% The Asphalt Institute. ethanol will be used. Ethanol is typically added to Technical_Focus_Areas/Important_Note_Recovering_Binders remove more asphalt from the aggregate. It is not _Containing_PPA.pdf. Accessed on October 20, 2009. B-1

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Transportation Research Board 500 Fifth Street, NW Washington, DC 20001 ISBN 978-0-309-21386-8 90000 Subscriber Categories: Highways Materials 9 780309 213868 These digests are issued in order to increase awareness of research results emanating from projects in the Cooperative Research Programs (CRP). Persons wanting to pursue the project subject matter in greater depth should contact the CRP Staff, Transportation Research Board of the National Academies, 500 Fifth Street, NW, Washington, DC 20001. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, or Transit Development Corporation endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP.