Heavy equipment machinery

Everyone from highway engineers to frustrated motorists has fantasized about a machine that would move steadily down a road, gobbling up bad pavement in front and leaving a trail of perfect pavement in the rear. No more construction backups. No more breathlessly expensive rebuilds. No more pockmarked, rutted roads waiting to break axles and bend wheels.

Although pavement recycling technology has not yet evolved to fulfill that fantasy, the industry is getting closer.

Cold planing, cold-in-place recycling, and hot-in-place recycling are accepted, widely used techniques for rehabilitating flexible pavements with surface course imperfections. Each delivers a piece of the road-renewal dream, leaving in the wake of its recycling train a smooth, flat surface that is accomplished relatively quickly and inexpensively.

In recent years, another recycling technology has gained popularity in North America — full-depth reclamation. It comes even closer to the road-renewal dream because it gives pavement managers a fast, inexpensive, long-wearing alternative to rebuilding roads that require major repairs or total reconstruction.

While the other recycling technologies grind off a portion of the surface course of asphalt and replace it, full-depth reclamation penetrates the entire flexible pavement section and a predetermined portion of the base material, uniformly pulverizing and blending them together to produce a stabilized base course. Thus, FDR can correct deficiencies in the base as well as the bound asphalt layers.

Full-depth reclamation technology can be utilized to depths of 12 inches or more; the most typical applications involve depths of 6 to 9 inches. As it pulverizes and mixes, the road reclaimer can also meter in precise amounts of additives to further enhance the structural characteristics of the stabilized base course. Its benefits start with the fact that FDR completely erases deep pavement cracks, eliminating the potential for reflective cracking. It also allows for cross-slope and profile grade adjustments, and road widening is easily accomplished.

The Evolution

At the heart of full-depth reclamation is a small fleet of road reclaimers, machines that use milling drums similar to those found on milling machines, but which are designed to cut and mix at much greater depths. Road reclaimers evolved from machines designed to handle mass production soil stabilization work. Indeed, the only difference between many of today’s reclaimers and soil stabilizers is the milling drum.

These machines have been in use in Europe and in North America for many years, but their suitability for FDR, North American style, has evolved with the advent of high-horsepower diesel engines. Powered by engines as big as 800 horsepower, today’s reclaimers cut harder and deeper, mix faster, and cover more ground than ever before. And with these improvements, popular FDR applications have broadened from low volume country roads to include city streets and medium volume roadways.

The classic application for FDR is a secondary or tertiary road with a 2- to 4-inch asphalt overlay on a compacted base. When the overlay is too deeply cracked or rutted for a mill-and-fill remedy, full-depth reclamation is the next cheapest alternative — and it can produce a much longer-lasting solution.

The full-depth reclamation process is fast and straightforward. A reclaimer pulverizes and mixes the asphalt and base material, creating a strong new base. The reclaimer is typically followed by a grader, a water truck, and various compactors. Minutes after the last compactor completes its pass, the road can usually be opened to traffic until the contractor is ready to apply the final surface treatment.

For some low-traffic roads, the surface treatment can be as simple as a double chip seal. For higher traffic roadways, the FDR operation is typically followed by an asphalt overlay, creating a new road that should have much better wear and load-bearing properties than the old road. More to the point, say FDR advocates, the new road is the equivalent of a traditionally rebuilt road in terms of life expectancy, wear, and load-bearing characteristics, but it costs a fraction as much and can be completed with far less interruption of traffic.

Full-depth reclamation can be used to rehabilitate and improve gravel roads, and it has also been used on major highways, including interstates. There have even been cases where a road was first milled, to reduce the bound asphalt depth to an appropriate thickness, so that FDR techniques could be applied. This milling is also sometimes done to allow for proper curb reveal on curb and gutter streets or to control grade prior to the subsequent asphalt overlay.

The full potential of full-depth reclamation is still being defined, but it has emerged as an important and valuable option for road managers to consider as they search for budget-stretching solutions to the thousands of miles of roads in Canada and the U.S. that can no longer be cost-effectively repaired.

http://www.wstabilization.com/download/files/What%20is%20Full-Depth%20Reclamation.htm

As anyone who lives in the Upper Midwest knows, roads and road repairs are a way of life. There’s no getting around it, especially in a climate that sees such wide temperature variances and growing volumes of heavy traffic.

Nowhere are these conditions more evident than in North Dakota, which endures severe winters that cause lots of damage to road surfaces. The state’s roadways also take a beating from vehicles with heavy loads, including semi trailer trucks, tractors and other farm implements.

The Maintenance Division of the state’s Department of Transportation gets a head start repairing all this damage with a crack pouring program while snow is still on the ground and highways are frozen.

"We use road oil, MC-3000 cutback oil, dump it into cracks to coat the edges," said Mike Kisse, program director. "The intent is to coat the edges so they won’t dry out and chip more. When the weather is warmer, the cracks will close. We also use this oil for chip sealing."

North Dakota DOT’s crack sealing program begins in early spring when temperatures rise above freezing. "We use polymer and chrome rubber to seal transverse cracks," Kisse said. "The rubberized asphalt is heated in a melter/applicator made by either Simline or Crasco. There’s a dispenser wand in the machine and the liquid is dispensed out of the wand and into the cracks. We level the cracks to finish it off and wait for it to cool, which seals the road."
Blow ‘N Go

The DOT also routes and seals cracks in a program nicknamed "blow ‘n go." A router cuts a groove into the crack to accept the same melted rubberized material. The crack is then cleaned out with compressed air. Next, heavy oil is sprayed into the open areas, followed by the melted polymer/chrome rubber compound.

"We don’t pour asphalt into a hole for patching," he continued. "We wash potholes and do hand patching and Scotch patching to keep potholes under control. If it’s a bad stretch of road, we’ll dig out an area, put gravel over it and get a paver patch in there and use hot mix over it."

The department does not mill asphalt or provide other major road repairs because it doesn’t have the equipment. These kinds of projects are done by contractors.

However, Kisse’s maintenance crews do micro-surfacing with equipment manufactured by Valley Slurry Seal. "We fill the depressed cracks with micro surface materials made of emulsion and very small aggregate to try and smooth out the depressed crack and improve the ride," Kisse continued.

"It’s a much more effective fix, compared to cold-mix pushes because the crack comes back. Micro surfacing material lasts quite a while and is a very fast process where we can move down the road and restore it in a short time."

The department also contracts out its asphalt overlays and some of its chip sealing, all based on available funding. "Federal aid allows us to provide one chip seal on all of our bare pavement roads," Kisse said. His maintenance crews also have equipment to do many of their own chip sealing projects.
The basic approach

South Dakota’s DOT divides the state into four areas, each area is divided into three regions and each region is responsible for the maintenance of roads within its boundaries, explained Greg Fuller, a DOT construction and maintenance engineer. Because each region has different road maintenance requirements, the DOT provides different budgets to each region to buy materials necessary for road maintenance.

"We do pothole patching in the summer with a truck full of patching material, shovel it into the potholes and compact it. In the winter, our main effort is snow removal and sanding to keep roads open," said Fuller.

Fuller’s office provides support services and state contract administration to select contractors who can supplement each region’s needs. "When a road project is too large for us in one region, my office will work on a low-bid contract and select the most qualified contractor." This is the basic approach that most states work under.

The DOT owns all trucks, front-end loaders and asphalt pavers that it purchases from equipment dealers.
Recycling is important

Mid State Reclamation & Trucking is a subcontractor, that works for prime contractors, which repaves roads. The company works in the Midwest area and is known for its reclamation of asphalt roads. "I think this is the second most recycled product in the United States, behind water," Donn Johnson, vice president, joked.

"We use Terex equipment, called asphalt reclaimers, for reclamation of asphalt roads. They take up a bituminous road section, mix it with the base material under the asphalt and make a homogenous blend that can be reshaped, compacted and used right on site instead of having to pick it up and dispose of it.

"The reclaimer goes all the way through the road. It mixes with the base material so you’re using 100 percent of what’s already there. We can add virgin material to the mix but, typically, we don’t. It’s a newer method to paving roads," explained Johnson. However, when needed, the company will add liquid products, such as emulsion, or dry products, such as fly ash and cement, to the mixture to make a stronger product.

With the amount of work that Mid State performs, it bought five Terex asphalt reclaimers in addition to milling machines and trucks. Clients include government agencies, restaurants, office buildings, condos, and apartments.
Not Just Milling Around

The use of cold planers and milling equipment for asphalt and concrete have been growing significantly since the equipment was introduced in the late 1970s. Advancements in sizes, variable depths and capacities, ranging from machines that can chew up a section of asphalt paving about 16 feet wide and several inches deep to mini-milling machines for small tight areas, have broadened applications dramatically and made them more economical.

By far the most popular is the front loading milling machines, which only requires one lane of a roadway to be shut down. Essentially there are five classes of milling machines: Class 1 to fix existing conditions, Class 2 for grade control, Class 3 for grade and slope control, Class 4 for full depth, and Class 5 for variable depth control.

The German company, Wirtgen, has developed a hot recycler milling machine that removes the top layer of an asphalt road surface, heats the asphalt, mixes it with binders and other materials, and lays a new surface all in one operation. The Model RX 4500 can grind a path from 10 feet to 15 feet wide to more than 2 inches deep.
Keeping Up Is A Click Away

With the changing landscape in road maintenance, equipment and methods, departments of transportation and private businesses have more and better methods to help improve road conditions across the country.

Training, re-training and just plain keeping up with how-to and what’s new in road maintenance and repair is the mission of LTAP, Local Technical Assistance Program. LTAP Centers are in 58 cities nationwide that provide a wide variety of training programs, workshops, seminars, and materials to help improve the skills and knowledge of local transportation agencies and private businesses and their employees.

The future of roads is on a smooth path.