Mike Robinson, Mark Maloney
Mark Maloney, 2009 recipient of the Gerald Rohrbach Pavement Conference Award for excellence in pavement research, announced that this year’s recipient of the award is Mike Robinson.
In an interview, Robinson, who has worked in several capacities at Mn/DOT, said his greatest interest has always been in materials research. He feels that his most important contribution in that area has been his effort to improve the quality of asphalt pavements. In looking at asphalt samples over many years, Robinson noticed that “the mixes would be dry. So I wanted to come up with a method for putting in the right amount of asphalt.”
The problem, Robinson said, is that “Everyone was specifying VMA [voids in mineral aggregate], which is based on maximum aggregate size—but there’s no correlation between maximum aggregate size and the gradation.” In response, Robinson developed the idea of specifying optimum asphalt film thickness (AFT) instead of VMA. “This is unique,” he said. “No other state than Minnesota uses AFT; the others use VMA, which was adopted as a result of SHRP [Strategic Highway Research Project].”
The benefit of the AFT approach, Robinson said, is that it allows a reduction of asphalt content through more careful control of the aggregate gradation.
— Richard Kronick, LTAP freelancer
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