"We were only assessed a minor completion penalty for finishing the project one day beyond the extended completion date," Bushong says. "But we also picked up some incentives for improving the ride quality (smoothness) of the road.
Without MDOT's approved change order to trench the shoulder and add three inches of the 2C mix, it would have been difficult to achieve the required density specifications. The change, which covered the cost of 4,000 tons of 2C mix and time to trench and reconstruct the shoulder, added approximately $100,000 to the original $2.75 million contract.
"With the shoulder compaction problems we experienced on the east portion of the project and the time it took to correct those problems, the change on the west portion was the only way to properly address the issue," Bushong says.
Since the project was a PWL (percentage within limits), mix designs, compaction densities and ultimate ride quality all had to fall under MDOT's standard project specifications for highway reconstruction.
According to Bill Adair, quality control supervisor for Rieth-Riley's Houghton Lake operation, the state's specifications are more disincentive than incentive in nature, designed to hold paving contractors accountable for achieving the acceptable quality parameters established by the DOT. Ride quality on this particular job was subject to an improvement of at least 40 percent.
Rieth-Riley achieved a 55 percent improvement. Any bump or dip that was greater than .3 inches had to be corrected. There were only four such deviations to correct on this particular job. Using the ride quality index to mathematically determine the project's smoothness, with zero representing a perfectly smooth surface and 100 representing an extremely rough surface, Rieth-Riley achieved an overall 24.81 RQI.
"When we performed test strips on the east portion of the project, we weren't achieving the density specs we wanted to achieve with the soft shoulder subbbase," Adair says. "The ‘blow' sand under the shoulder pavement was not allowing us to compact the new leveling course to the density requirements we had to meet. Once we convinced the DOT that we had to trench out the shoulder and replace it with three inches of the 2C mix (one-inch aggregate), we were then able to hit our density numbers."
On the 4E3 (3/4-inch maximum aggregate) intermediate leveling course and the 5E3 (1/2-inch maximum aggregate) wearing course, both containing 5.3 percent of PG 64-28 asphalt binder, density and smoothness specifications were achieved on the travel lanes and the shoulders once the subbase conditions were corrected. The intermediate mix design contained 16 percent reclaimed asphalt pavement and the wearing course contained 10 percent RAP.
Rieth-Riley's paving crew used a Blaw Knox 5510 track paver to place the 2-inch leveling and the 1 1/2-inch wearing course. Because of the long 55-mile haul from Rieth-Riley's Roscommon asphalt plant, Bushong had to establish an aggressive rolling pattern to achieve density before the mix cooled. He used two Ingersoll-Rand DD 110s for initial breakdown, followed by a Dynapac 522 and Dynapac 422 for final compaction and smoothness.
"We used a material transfer vehicle when placing the three-inch shoulder mix, but on the mainline paving work we relied on an aggressive rolling pattern to achieve density specs before the mix cooled down." Adair says. "We were required to conduct four core samples for every 750 tons of HMA placed and pull a sample mix off the truck every 750 tons. The state pulled its own QA sample every 750 tons as well.
"The job produced minimal disincentives and we were able to achieve the improved smoothness criteria the contract specified," Adair adds. "All in all, we were very happy with the final results."