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Compositional evaluation of asphalt binder recycling agents
Abstract
Several experiments were performed to determine how recycling agent composition affects the high, intermediate, and low temperature properties as well as long term oxidative aging characteristics of recycled asphalt blends. Specifically, several deasphalted oil samples, commercial recycling agents and supercritical unit top fractions were separated into two distinct aromatic and saturate fractions. The aromatic and saturate fractions were then blended, in controlled amounts, with artificially aged SHRP asphalts. The long term oxidative aging characteristics of each blend were evaluated using the hardening susceptibility (HS) parameter, while Superpave TM Performance Grades were used to evaluate the high, intermediate and low temperature properties. The recycling agents consisting of saturate and asphaltene-free aromatic fractions improved the hardening susceptibility of recycled asphalt binder blends. Dilution of the aged asphalt along with the composition of the recycling agent were found to be key parameters in improving the hardening susceptibility of recycled asphalt blends. In addition, recycled asphalt blends made from saturate and asphaltene-free aromatic recycling agents possessed improved hardening susceptibility values over using a new asphalt binder. The high temperature Superpave TM Performance Grade (PG) specifications for recycled asphalt binders were found to be highly dependent on the aged asphalt. In addition, as the amount of saturates in the aromatic recycling agent increased, the upper and intermediate PG specifications decreased. The low temperature PG specifications deteriorated as the amount of aromatic recycling agent increased, and an opposite trend occurred when the saturate content of the recycling agent increased, thus indicating that the mere presence of saturates improve the low temperature PG of recycled asphalt blends. The performance grades of the recycled blends were all superior to the PG of the original asphalts and superior to using a new asphalt binder. The data indicate that although two completely different blends may have equivalent PG, and therefore similar performance properties, they can have vastly different HS values. In conclusion, a compromise must be made between performance grade and hardening susceptibility, since the data indicate that saturates improve the PG while deteriorating the HS.
Description
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Citation
Madrid, Richard Charles (1997). Compositional evaluation of asphalt binder recycling agents. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1997 -THESIS -M334.
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