New Approach to Recycling Asphalt Shingles in Hot-Mix Asphalt
Publication: Journal of Materials in Civil Engineering
Volume 24, Issue 11
Abstract
The objective of this study is to introduce a new approach to recycling asphalt shingles in asphalt paving construction in which recycled asphalt shingles (RAS) are ground to ultrafine particle sizes and blended with asphalt binder through a wet process. In the proposed wet process, the ground recycled material is blended with the binder at a high temperature prior to mixing with the aggregates. Two unmodified binders that are classified as PG 64-22 and PG 52-28 were blended with two contrasting sources of RAS at a modification content ranging from 10–40% by weight of the binder. The use of RAS modification through the proposed wet process was successful in the laboratory. Based on the results of the experimental program, the use of RAS modification through the proposed wet process would generally improve or not influence the high temperature grade of the binder, but it may reduce the low temperature grade of the binder. As demonstrated in this study, an optimum shingle content may be identified that will improve the high temperature grade without influencing the low temperature grade of the binder. Using confocal laser-scanning microscopy (CLSM), wax crystals ranging from 4–8 μm in size were successfully detected. However, wax crystals were not detected in the RAS-modified binder, which may indicate that the wax molecules are absorbed by the RAS material. Results of high-pressure gel permeation chromatography (HP-GPC) showed that the proposed wet method of modification produced a slight increase in the high molecular weight (HMW) () content in the prepared blends at higher RAS contents, suggesting that a fraction of the RAS binder contributes to the blend properties.
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Acknowledgments
This research was funded through the National Science Foundation (Grant No. CMMI-1030184). The authors would like to acknowledge the assistance of M. Vaughn, S. Robins, S. Cooper, and M. Brown of Louisiana State University and W. Gueho of LTRC.
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© 2012 American Society of Civil Engineers.
History
Received: Oct 19, 2011
Accepted: Mar 19, 2012
Published online: Mar 21, 2012
Published in print: Nov 1, 2012
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