In spring of 2016, Blackrock Milling LLC of Tampa, put two of its cold milling machines to work in echelon to remove more than a million square yards of aged pavement from Interstate 75 near Ocala. The project encompassed 19 miles of six lanes, plus 10-foot shoulders on the outside and the medians, plus exit and entrance ramps. In early May, Blackrock had completed all inside lanes and shoulders, milled 2.5 inches deep. The center and outside lanes were milled 3.75 inches deep, while the outside shoulders were milled 1.5 inches.
“There are some areas where the outside shoulder will be milled at 3 inches,” said George Smith, vice president of Blackrock. “It’s over a million square yards of asphalt, all done at night.”
On I-75, Blackrock was following the existing crown and inverts in the pavement, Smith said. “Some areas of slope needed correction on superelevated curves, but generally we followed the existing slope throughout the project,” he said.
After asphalt was milled by Blackrock, the pavement would be swept and fresh lifts of HMA would be placed the same night by prime contractor Anderson Columbia Inc. RAP from the project was being stockpiled by Anderson Columbia for ultimate use on other projects.
The Florida Department of Transportation (FDOT) permitted single lane closures at 8 p.m., with barricades removed by 6 a.m. Double lane closures were permitted at 9 p.m. and picked up at 5 a.m. Milling had to stop by 2 a.m. to allow the prime contractor time to finish placing and compacting HMA driving surfaces for rush hour traffic.
On I-75, Blackrock used two W 210i cold mills with 7-foot, 3-inch drums from Wirtgen America Inc. Using the two W 210i mills, Blackrock was averaging 11,000 square yards per shift ending at 2 a.m.
“The biggest challenge on the job is lighting,” Smith said. “On rural interstates there usually are no light standards, and we supply our own illumination. Traffic is another big issue at night, as you are working in such a confined area. When dump trucks are trying to get out in the live lanes after being loaded, heavy traffic can make it difficult.”
Blackrock uses the standard Wirtgen lighting packages for its machines, in addition to extra LEDs to help with local lighting. “All the light that comes from the standard Wirtgen package lights up the work zone quite a bit,” Smith said. “And of course we run strobes on all of our equipment.”
Expand the Business
Blackrock has been in business for four years, but management is no stranger to the industry. Pete Hernandez, president, spent years in asphalt paving in Florida before launching Blackrock for the Florida market.
“I founded Blackrock in 2011,” Hernandez said. He had an asphalt production company in Tampa, which he sold to a publicly traded company. “I stayed on a few years, and started Blackrock after.”
It’s based in Tampa, but Blackrock has facilities throughout the state, from which it can mobilize equipment for any job. Currently, Blackrock has 11 crews to operate its fleet of 10 mills. In May, the company was in the process of acquiring another W 210i, for a total of 11 mills. That machine was destined for the Dallas-Fort Worth area, where Blackrock began operations this year.
“We’ve become the largest milling contractor in Florida,” Hernandez said.
“We started our business with one crew and one mill…” Smith said. “We soon decided to switch over to Wirtgen with two W 210s. We’ve grown steadily since then and have owned only Wirtgen mills.
“With our first machine, you had to lower the rear end manually into the ground, and then as the rear tracks walked into the cut, you had to bump it to zero,” Smith explained. Wirtgen technology labeled parallel-to-surface (PTS) is designed to simplify such moves in and out of cuts. “With PTS, you don’t have to do that. It lowers everything evenly, and as the rear tracks walk in, the rear end self-rises to level. It’s just one thing removed from the equation, one less thing for a new operator to worry about. PTS also comes in handy when jumping over manholes and water valves.”
For an interstate like I-75, the crew won’t find manholes or water valves to work around, but scheduling remained a hot button.
“The number of mills we have doesn’t necessarily correlate with how many crews we have working from day to day, because a lot of them are double-shifted,” Hernandez said. “They’ll work a day shift, and then a night.
“Logistics is the biggest barrier to making it happen,” he added. “It doesn’t work for the entire fleet, but we stay top-heavy on personnel, so we can accommodate our customers’ schedules. If we are in the same town, and we have jobs at night there, but there is a need for work in the day within the same geographic area, we can double-shift the mill because we run staff-heavy.”
“We do double-shifting all over Florida,” Smith said. “Daytona…the Panhandle, wherever the schedules and the needs are. We run heavy on personnel so we can double-shift the equipment, not our employees.”
Blackrock Gets Eco-Friendlier
The W 210i—unlike the same-sized W 200i—has two diesel engines powering the machine. When both engines are employed, an extraordinary amount of power is available for tough milling situations, or faster milling on long stretches of interstate highways. For lesser applications, the single engine can be used to stretch fuel consumption in an Eco mode.
“We run our machines in Eco mode 90 percent of the time, as it helps save fuel, minimizes tooth wear, and removes stiffer asphalt better in Eco mode than if it were revved all the way up,” Smith said.
In Eco mode, on I-75 doing an average of 11,000 square yards per shift, Blackrock was burning roughly 80 gallons of fuel per night per machine. “Fuel consumption is good, and that’s because of the Eco mode,” Smith said.
If its W 210i is doing shallow cuts, or doing a friction treatment or shaving high spots (profiling), Blackrock will rev both engines all the way up to get a faster-turning drum, and a cleaner cut, Smith said.
That matters when thinner asphalt lifts are going over the milled surfaces. As promoted by the Asphalt Pavement Alliance, Thinlay lifts are conventional layers of asphalt placed as little as 5/8-inch thick. “For these it’s important to provide as smooth a pattern as you can, so they won’t get too rough a ride on the structure,” Smith said. “With the drum speed turned all the way up, and the forward speed relatively slow, the result will be similar to a micro milling drum.”