Investigation of low- and high-temperature properties of plant-produced RAP mixtures (report) publication number: FHWA-HRT-11-058.
This report documents a two-phase study of performance properties of pavement mixtures containing high levels of reclaimed asphalt pavement (RAP). Researchers evaluated plant-produced mixtures with high RAP content (25 and 40 percent), different binders (PG64-22 and the softer PG58-28), and a control mixture with no RAP The study improved the understanding of the performance characteristics of hot-mix asphalt (HMA) mixtures with RAP at high, intermediate, and low temperatures and examined plant-produced HMA mixtures containing RAP.
Test results on binders extracted and recovered from the plant-produced mixes showed that as the RAP content in the mixture increased, the high-temperature grade of the recovered binder also increased, but only by a few degrees (5.4-10.8 [degrees] F [3-6 [degrees] CD. The low-temperature grade of the recovered RAP binders also increased, but not by as much as the high-temperature grade. The use of a softer virgin binder grade typically decreased both the high- and low-temperature grades of the recovered binders by half a grade or more. Also, increasing the RAP content to 25 percent changed the low-temperature grade of the recovered binder by no more than 3.6 [degrees] F (2 [degrees] C) compared to the binder recovered from the virgin mix (with no RAP).
Use of a softer virgin binder grade (PG58-28) typically reduced the stiffness of the mixes. Tests of the mixtures showed that the critical cracking temperatures of the mixes with PG58-28 were much lower than those of the comparable mixes with PG64-22 in two of five cases. In the other cases, they were comparable. Although the softer virgin binder grade resulted in an increase in the fatigue life at 25 percent RAP, it did not have as strong an effect on the 40 percent RAP mixes. The mixes with 40 percent RAP exhibited the greatest fatigue lives in many cases. The fatigue life increased as temperature increased at a given strain level, but fatigue life was less sensitive at lower temperatures. At the two lower temperatures tested, the predicted fatigue life was the same for all mixtures regardless of RAP content or virgin binder grade.
The full report is available at www.fhwa.dot.gov/publications/research/infrastructure/pavements/11058/index.cfm. Printed copies are available from the PDC.
Compiled by Michael Thotyn of FHWA's Office of Corporate Research, Technology, and Innovation Management
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|Title Annotation:||Communication Product Updates; reclaimed asphalt pavement|
|Date:||May 1, 2012|
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