No Fiber Diet for SMA
Sep 17, 2011
The Chester Bross portable plant in River Bend, MO, made stone matrix asphalt (SMA) with Evotherm and without fibers. Paving was 10 miles away in the shadow of Harrod's Casino in northern Kansas City. Losses may have been brisk inside the casino, but the gamble taken by Chester Bross and MoDOT to run Evotherm at 280F without fibers hit the jackpot.
Starting hot at 310F and gradually dropping to 280F, the crew were able to overcome 2" of rain that had fallen since the weekend and hit both voids and AC content in the lab with only very minor adjustments. The binder was rubber modified resulting in PG 76/-22; target voids of 4% and binder content of 6.4%.
Reported densities of 95+% were obtained in the field. Screed temps ranged around 260-240F. Density was achieved with the breakdown rollers eliminating the need for an intermediate or finish roller. Traffic was able to pass at 120F, and cores were also taken at around this temperature.
Photos at the jobsite show a very coarse, open structure typical of SMA. Five to seven passes with vibratory compactors left the 2" mat looking very solid but still showed the surface voids notable for this mix.
The lower temperatures for Evotherm WMA in an SMA and running without fibers were firsts for everyone. For mixing and compaction with Evotherm, it was just another night on the town. To put your asphalt on a "no fiber" diet, contact MWV at mailto://[email protected]
Author: Michael Plouff