Loading

Full implementation of Multiple Stress Creep Recovery (MSCR)

A look at three Northeast U.S. states

By Greg Harder, P.E.

Back in the early 90s the advent of Superpave gave us a performance-graded (PG) binder specification known as AASHTO M320. The new PG specification considered the climate including both high and low pavement temperatures, traffic loading rates including both speed and volume plus incorporated aging of the binder within the testing framework to consider the binders performance with respect to permanent deformation and cracking.

Developed around neat asphalt binders, it was soon recognized that M320 did not properly characterize modified binders – especially those modified with elastomeric polymers. The PG specification was refined with the introduction of the Multiple Stress Creep Recovery (MSCR) test (AASHTO T-350) along with its corresponding specification AASHTO M332. While this change has been a significant improvement in the characterization of asphalt binders, its implementation nationally has been quite slow. (more…)

Asphalt Academic – John Harvey

We talk with leading educators in the field of asphalt technology in an effort to connect with academia on important industry issues. 

Dr. John Harvey, Ph.D., P.E. is a professor at the University of California Davis where he directs the UC Pavement Research Center.

What drew you to transportation engineering?

Working with soil and construction equipment, as well as movement of water, people and things entertained me as a kid. There were no engineers in my family. My dad was a history teacher and my mom was a business secretary/goat rancher/hardwood floor contractor. I was originally a music major in college, but got interested in the engineering of roads and streams while working as a firefighter for the U.S. Forest Service. I dropped music, caught up on math and science and became a civil engineering major. I was interested in building canals to move water and roads to move people. The best job offer when I graduated was in pavement. (more…)