Using the coarse base mix increased the potential of material segregation. Pulling the mix from its Marrysville/Dantoni plant left DeSilva Gates with an hour and fifteen minute one-way travel time to the Highway 70 jobsite, which allowed portions of the mix to cool 25 to 50 degrees on the trip. "Under these conditions it would be next to impossible to successfully meet spec densities with a conventional paver," comments Matt Herrmann, vice president of Herrmann Equipment Inc., a Terex/Cedarapids paver dealer.
Long hauling distances and resultant thermal segregation are nothing new to DeSilva Gates, as the contractor now routinely trucks material over an hour to supply asphalt to its paving jobs in the Sacramento, Roseville and Auburn areas. Prior to purchasing the Remix paver, the paving crew had experienced problems with both thermal and material segregation when using the company's conventional slat-delivery pavers.
However it wasn't until a demo of the Remix paver on an application in Oakland that DeSilva Gates learned the benefits of reblending the material. "They had problems meeting spec densities on that job prior to the demo," recalls Herrmann. "During the demo, the Port of Oakland inspectors thought DeSilva Gates fixed the problems at the plant, but the only change was using the Remix paver instead of a slat paver."
Purchasing the paver and using it on Highway 70 proved advantageous for DeSilva Gates. "Reblending the material with our Remix paver has eliminated the thermal as well as material segregation that we experienced in the past," says Jim Alves, paving manager for DeSilva Gates. "Now temperature differential across a 20-foot mat is less than five degrees, making it easier for us to meet spec densities."
Across the country in Buffalo, NY, Holmes and Murphy purchased a Remix paver specifically for a difficult paving job at the Buffalo Niagara International Airport (BNI).
The $12-million project required 125,000 tons of asphalt to, among other projects, upgrade the crosswinds runway from Class B to Class A, lengthening it by 1,200 feet and installing an ILS system, so commercial aircraft can land. Due to the demands exerted on the runways and taxiways of an airport, the work at BNI followed stringent guidelines and included a Federal Aviation Administration (FAA) mix design, which demanded discipline placement.
More than 57,000 tons of a P-401B base course mix, consisting of a 2-inch minus coarse aggregate, was laid in two lifts, the first at four inches and the second at three inches. This FAA mix gets it strength from the aggregate and consists of less binder and fewer fines than a typical Department of Transportation mix.
While the 2-inch minus base course gets its strength and durability from the coarse aggregate, without disciplined placement it has a potential to segregate. This was a concern for Holmes & Murphy that never materialized. "The Remix paver handled any segregated mix coming out of the truck," says Culver.
Although the trucking distances were not as long at the BNI job as experienced with DeSilva Gates' Highway 70 application, mat temperature uniformity behind the paver was still a priority. The FAA required Holmes & Murphy to achieve a minimum 96 percent density across the mat and 92 percent density at the joints. According to Richard Holmes, president of Holmes & Murphy, "Our performance expectations of the Remix Anti-Segregation System were very high. The paver met our every expectation, and it helped us to meet the spec."
The paver's capability of reblending the aggregate delivered the additional benefit of making mat temperatures more uniform. "We used three methods to measure both surface and internal mat temperatures," explains Culver. "Mat temperatures at BNI were very uniform behind the Remix paver."
A significant key to successfully meeting spec densities in a performance-based contract is the ability to reblend material that has segregated during transport. Uniform aggregate distribution throughout the mat will lead to a stronger, longer lasting road.
Better temperature distribution across the mat allows both the screed and rollers to achieve higher densities. "We achieved 85 percent density behind the Remix paver," comments Culver. The higher the density achieved at the screed translates into less time the rollers have to be on the mat to meet spec.