ASPHALTopics | Summer 2014 | VOL 27 | NO3

y Lisa Fattori
in
April 2014, OHMPA published Ontario draft contract language for the new Multiple Stress
Creep Recovery (MSCR) graded asphalt cement. The material specification replaces the Superpave
Performance Graded (PG) asphalt binder specification and has been identified as MGAC (MSCR
Graded Asphalt Cement) to avoid confusion. The MSCR procedure improves upon previous testing
methods to provide information about both the performance and formulation of the asphalt binder
through a single test. For heavy traffic areas that require elastomeric polymers in the binder,
the test provides a more accurate assessment of how the asphalt cement will perform.
“We’re always looking for improved tests for both
high and low temperatures, and the existing test didn’t
capture all of the characteristics of modified systems,”
says John D’Angelo PhD., CEO of D’Angelo Consulting
LLC in Washington D.C. “This test is an improvement
because it looks at both modified and unmodified binders.
The previous test used the same equipment, but just
looked at low stress levels – small loading and movement
– and didn’t capture how the AC would react under high
traffic or stress levels. This test gives us a lot more detail;
performance characteristics under high temperatures
and if elastomers have been added to the mix.”
While working at U.S. Department of Transportation’s
Federal Highway Administration (FHWA), D’Angelo was
part of the research team that developed the MSCR
specification. The research project began in 1999,
with finalized test results submitted to the American
Association of State Highway and Transportation
Officials (AASHTO) in 2008. AASHTO published the
MSCR test procedure as a provisional specification,
and conducted trials for another six years. Since 2009,
the MSCR test has been available, with a number
of jurisdictions developing their own methods of
implementing the specifications.
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