Even Coats: Tack coat sprayer an integral part of road paving even coats

By: LeeBoy

The major items of work on this project include the widening of the existing turnpike from four lanes to six lanes and installation of approximately 34,000 tons of asphalt, which include the following asphalt mixes: FDOT Type 12.5 MM Traffic Levels B, C and D and FDOT Type FC-5. The work also involves the construction of a fly-over bridge crossing the turnpike and widening of the existing turnpike bridge. Todd Harrison, the Maximizer 3 operator on one particularly challenging section of the complex project, as well as being paving foreman, said with the unit’s in-cab EZ-3 control system, he was able to make two side-by-side 15-ft-wide passes.

This width started from a concrete bridge deck intersection down to the bottom of a long hill that narrowed to only 10 ft wide. The new Maximizer 3 was spraying the tack under high pressure so as to produce a uniform tack coat to better help bond the FC-5 friction course. The somewhat porous “popcorn” course permits surface water to pass through interstices for better drainage to reduce vehicle hydroplaning.

Typical of the commercial and residential projects where the Rosco Maximizer was used was a recently completed $1.6 million contract on U.S. Rte. 17/92 in Winter Park where Middlesex was the general contractor. Because of the area’s heavy daytime traffic, the work was mandated by FDOT to be completed at night. The major items of work include milling 2 in. from the existing roadway and resurfacing it with two 1-in. courses of asphalt plus a complete tack coat application after mechanically sweeping the milled roadway. The project was done on an existing 5 miles of secondary roadway through a commercial-residential area.

This job called for the installation of approximately 11,000 tons of Superpave asphalt, which included FDOT Type 9.5 MM Traffic Levels C and FDOT FC -9.5 MM friction course. The prepaving preparation also included the installation of approximately 56 individual handicap access ramps.

“The tack coat, applied with our Rosco Maximizer 3 , is a very important operation to the final integrity of the new highway. It was applied at between .04 to .06 gallons per square yard. Ideally, traffic permitting, we could put this down a thousand feet ahead of the paver. This gives us about 10 or 15 minutes for the tack to break depending upon the ambient heat and humidity. At night, the operator also uses an installed small TV monitor used to view the back of the truck to ensure the asphaltic emulsion is being put down correctly and evenly. It is a comparatively simple operation, requiring a degree of skill to apply properly. But it is a very important aspect of building a long-lasting road or highway,” concluded Robert Pereira Jr.

The Maximizer 3 was spraying the tack under high pressure so as to produce a uniform tack coat to better help bond the FC-5 friction course. At night, the operator uses an installed small TVmonitor used to view the back of the truck to ensure the asphaltic emulsion is being put down correctly and evenly.