A Clean Sweep

By Gini and Dan McKain | September 28, 2010

While there have been many recent technological advancements in hot mix asphalt (HMA) surfacing and resurfacing projects, very few things have ever had the impact of an old-fashioned, clean, tight, bond between asphalt lifts on a roadway's longevity. It is also a well-established fact that the American taxpayer is the ultimate beneficiary in a contractor's effort to put down a longer lasting roadway surface, as Belle Chase-based Barriere Construction Co.'s South Shore Asphalt Division recently demonstrated. It took place on a $3.5-million, 4-mile-long, milling and resurfacing job on a section of Belle Chasse Highway (La. Highway 23) at Pointe a la Hache, near Port Sulphur, Louisiana.

Barriere earned the low bid resurfacing contract with LDOTD on a roadway for which they had already won a top National Asphalt Pavement Association's "excellence in craft award" a quarter of a century earlier. In between the two events, the state had expended no major maintenance funds on the stretch of highway.

Often all but overlooked in the importance of a major hot mix asphalt-paving project are the "little details" that make the difference between just another blacktop job and an incentive-earning, award-winning, roadway-resurfacing project. As most experienced asphalt contractors are well aware of, it's most often the little things that can make the big differences. These can range from the temperature of the mix from the plant to the project, to the smoothness and cleanliness of the milled mat to be resurfaced.

Sweeping Technology

Broce Manufacturing Co. from Dodge City, Kansas, has recently addressed this latter problem. They introduced their new MK-1 transfer sweeper that both cleans the milled surface and outloads the debris, dust and milling remains from the job just ahead of the paving train. It's a minor operation that plays a major part of an incentive-winning mat!

The clean sweeping of any residual debris following the milling of an about-to-be-resurfaced highway is one of the most important phases of the job. Without it, the longevity of the new road surface becomes suspect. It has been shown that among the best ways to accomplish this is with the use of a modern mechanical broom.

On the recent milling and resurfacing project on Route 23 in Plaquemines Parish, Louisiana, about 30 miles south of New Orleans, Barriere Construction Co, used three Broce mechanical brooms. They were working in an echelon formation, very close behind the milling machine and only slightly preceded the asphalt paving train.

A Broce MK-1 Transfer Sweeper with conveyor and a separate dump truck immediately followed two Broce CR-350 brooms that were working in a stepped overlay formation in order to sweep the newly milled surface clean of all remaining millings and other debris. These three American-made (Dodge City, Kansas) machines, immediately following the contractor's two Roadtec milling machines, preceded the tack truck in front of the Roadtec SB-2500 Shuttle Buggy and Cat AP-1055D laydown machine. This was done to give the newly milled surface a final sweeping before the actual asphalt placement.

The Broce MK-1 Transfer Sweeper is designed not only to sweep debris off the roadway, but also to remove and load the material into a dump truck in a continuous operation. The MK-1 can load to a height of 10 feet 6 inches straight ahead or to either side.

There is an advantage to using the MK-1, according to Ben Tucker, equipment manager for Barriere. "You have to make sure that the surface after the milling process is clean of all loose debris so that the tack coat and asphalt have a permanent and solid base to adhere to. It can eliminate the ripple effect on the finished hard mat in the long term — meaning months and years after placement."

"By picking up debris from the road after milling, it prevents small stones from getting picked up in tires or snapped into car windshields, causing problems and becoming a public safety issue," according to Nelson Capote, project engineer with the LDOT. "A clean surface is essential for proper adhesion to the binder, and as a result, the road will last longer."

Tucker further explained that they go with the Broce Brooms because of their products' high reliability. "We have been using them since 2002 and have about 18 Broce Brooms throughout the company. They are mostly CR350 machines, and now we have the MK-1. This machine has been used behind our milling machine for about eight months now, to pick up the remaining millings."

Mathew Woods, division manager for the South Shore Barriere Co. said that there is an extremely minimal loss factor of millings behind their Roadtec RX900 machine by using the MK-1. "It was 8 to 9 percent before using the MK-1. Now it is, however, only 2 to 3 percent, if that."

Pays For Itself

Tucker said the importance of that amount equates into money.

"The MK-1 pays for itself by loading excess millings left behind and not swept to the shoulder, which had been done in the past. We get paid for those milling in our contracts. If we load 10 trucks a day of milling material from the MK-1, and send it back to the plant for future recycling, it all adds up to dividends at the end of the project."

"We used to run a vacuum sweeper, but the maintenance cost and reliability was just too high. Now we use the MK-1. We are not polluting storm drains or the area with leftover millings, as had been a practice in the past. This method is more environmentally friendly, and it leaves our milled road with the cleanest surface possible," Tucker concluded.

Milling Procedure

All this was done as a most important step in order to assure a clean, dry roadway for the new asphalt to bond with the milled surface. These were just several of the many steps taken by Barriere crews to help produce maximum roadway longevity.

Barriere began the Route 23 work by first milling off and recycling 1.5 to 1.75 inches off the old asphalt with the Roadtec cold asphalt planers. To do this work, the contractor relied on its new RX-900 Roadtec milling machine plus a new, smaller Roadtec RX-700 that it was evaluating for one of its other divisions.

Milling supervisor Jeff Heickemper said that with the two Roadtec machines working together they were able to mill one full 12-foot-wide lane length a day. The depth of the cut averaged 1.5 inches deep with a little more where a slight change in slope of .025 percent entered the equation. The specifications divided the millings 25/75 percent to the state-contractor split. Barriere used some of its millings as fill, down near the town of Venice in the hurricane-ravaged areas. The remainder was trucked back to the asphalt plant site for recycling.