Personalized Paving

Slipform pavers are versatile enough that they are used for just about any paving job these days. With the diversity of sizes and the availability of kits and molds that change the abilities of a particular paver, you can do everything from curb and gutter to guardrails, barriers and multi-lane highways - sometimes all with the same machine.

?There are so many contractors who do so many different jobs with their machines,? says Tom Devonshire, Terex Roadbuilding. ?For example, a mid-range, four-track paver such as the 3504 can be converted to do 12- to 36-ft. paving widths. It can also be fitted with barrier molds. It?s all in the utilization of the equipment.?

Versatility certainly enhances today?s machines. Kent Godbersen, vice president of worldwide sales and marketing, GOMACO, notes that GOMACO units feature pivoting legs for variable track placement, enabling them to adjust to varying jobsite conditions and easing transport. And for easy, accurate bar placement, insertion bar system options range from those with hydraulic cylinders to air- or manually-powered units. The systems can also be frame mounted, side mounted or inserted with a trailing form. The In-The-Pan Dowel Bar Inserter (IDBI) fits within the length of the paver - it doesn?t require massive rear extensions to the paver frame.

Frames that widen hydraulically make width changes easier. For example, GOMACO?s dual telescoping V2 variable-width mold will make on-the-go width changes for tapered slabs.

Terex?s Series 6 slipform paving kit eliminates conventional nut-and-bolt connections by utilizing a wedge and pin locking system. Widths can be changed relatively quickly, allowing the paver to ready to work in hours rather than days.

According to Devonshire, time was of the essence on a Texas job last summer, which was delayed more than 30 days because of rains that flooded many cities around the Dallas jobsite. A big concern for the contractor was reducing paving time while still meeting tough ride specs.

The Series 6 paving kit helped save time because it could be used to do all of the mainline paving, which required paving at three different widths. By using the kit, the contractor estimates he saved 2.5 days.

No easy answers

With various sizes of machines offered, as well as options, sorting out which machine is the best choice for which job isn?t always easy. ?There are no simple answers,? Devonshire says, noting that when combined with the number of tractors available, the page count for listed options of Terex machines nears triple digits. ?You will always have a basic machine configuration. But contractors don?t buy a paver off the shelf. There is always something unique about every project.?

The selection process requires knowing what the immediate and future project requirements involve, notes Godbersen. He recommends asking yourself questions such as: Are there tight clearances involved? Are width changes required? If so, how easy is it to change the paver width? Does the paver have hydraulic frame widening to help accomplish width changes? What is the required ride specification? Is the control system easy to learn and operator friendly? What are the bar insertion capabilities? How easy is the machine to transport?

In addition to these questions, Fred Hite, Power Pavers, adds that concrete depth, width and tolerance limits related to smoothness should also be considered.

Smoothness is playing an increasingly important role in paver selection, since most jobs have smoothness bonuses and/or penalties tied to them. ?Ride specs are driving a lot in paver selection,? says Devonshire. ?The smoother the ride, the higher the bonus.?

There are many factors that go into achieving smoothness, including the size and weight of the machine. Usually, the heavier machines with higher horsepower ratings will yield a smoother road, especially for deeper, wider slabs.

?If you?re paving 8-in. slabs, because of the hydrostatic pressure of the concrete, you can have a little bit lighter machine,? says Devonshire. ?But if you?re paving 18 in. deep and multiple lanes on a zero blanking band or IRI spec, then a two-track paver may not have sufficient weight and horsepower to move enough concrete or withstand the hydrostatic pressure of the concrete to keep the paver on grade.?

The pressure will build up and cause the tracks to spin out, which could affect ride quality. ?You want as much weight as possible for thicker slabs,? he advises.

Some contractors will only use a four-track paver for mainline paving because ride specifications are so tight, Devonshire states. ?Some will even use it to pave lanes that are just 12 ft. wide because it can pave faster, it?s accurate and you get great smoothness. The weight of the four-track paver is distributed better, and four tracks maintain traction better than two,? he says.

However, either type can be effective. ?All pavers, two- or four-track, are capable of meeting ride specs under the right conditions,? Devonshire concludes. ?There are many determining factors for successful paving, but some of the most important are a sound, accurate foundation, a well-maintained stringline, appropriate equipment (plant and paver) and a well-trained crew.?

When bigger isn?t better

While size and weight can enhance smoothness, it isn?t always best to use the largest paver available. ?Jobsite conditions, such as a stable track line that is capable of supporting a heavier mainline paver, clearance from the back of the pavement, cul-de-sacs or obstructions often make it more advantageous to use a smaller paver,? says Hite.

Logistics also factor into the equation. How much room do you have to maneuver a paver into the jobsite, asks Devonshire. Can you drive it off a trailer or do you need a crane to unload it? ?If you?re using a full-size four-track mainline paver in a residential cul-de-sac, you may not have enough room to maneuver it,? he points out.

Also consider logistics outside of the unit itself, says Hite. ?The biggest factors in paving are consistent supply or delivery of the concrete and consistency of the concrete mix,? he comments. ?If a consistent, continuous supply of concrete cannot be maintained to keep the paver moving continuously, if access is limited, paving half width should be considered. An even, compacted surface for the crawler, an accurately set and undisturbed stringline, as well as a crew working in sync are also critical.? ?

Get It Right From the Start

Many paving projects start with curbs and gutters. Because they set the grade for the entire job, getting them right is important.

While some mid-range pavers can be equipped for this application, it is often handled by designated curb and gutter units. Yet, many of these units aren?t limited to curb and gutter, since they can often pave flat surfaces, as well. For example, the Curb Fox units from Messinger, Inc. can pave flat surfaces up to 5 ft. wide. And Power Curbers units can pave flat surfaces up to 10 ft. wide. Fitted with specialty molds, they can also slipform unique formations.

?As contractors get creative, we can work with them to develop appropriate mold designs and application setups to make their machines more versatile for a variety of jobs,? indicates Steve Milam, Power Curbers. ?The role these machines fill is for the contractors who aren?t doing wide highway paving. The curb machines effectively do everything else. They can do all different styles of curbs and gutters, sidewalks, barrier walls and some unique applications, such as stadium risers, irrigation ditches, etc.?

Like their bigger brothers, selection of curb and gutter machines is based on evaluating the type of job at hand, says Tim Messinger, Messinger, Inc. Typically, they fall into two categories: those with built-in trimmers and those without.

Curbing contractors commonly roll onto jobsites where the grade may not be properly prepared, notes Milam. A larger curb and gutter machine with an on-board trimmer can accurately cut to final grade without having to wait on the dirt contractor. Since a larger machine can do more jobs, it can stay more productive.

?Curb and gutter contractors will usually do some of the grading,? Messinger agrees. ?In areas where the grade is rough, the manufacturer may have a trimmer built into the machine to achieve the final grade. Otherwise, final grade can also be achieved with a motor grader or skid-steer loader. While a larger curb and gutter machine can do more jobs, they cost considerably more.?

To determine if the investment in a larger unit is wise, Messinger advises evaluating how many lineal feet you normally place. ?If you?re just doing 20,000 to 25,000 lineal ft., you likely won?t be able to justify the investment,? he says. ?It?s hard to say where the cutoff point is. But if you?re doing large volumes - maybe 100,000 lineal ft. or more - you may have a large and small unit anyway.?

While a larger unit can cut to grade, a smaller unit has the upper hand in mobility and maneuverability, which is important when turning tight radii. Smaller units can also be transported with a pickup truck and trailer since they only weigh up to about 7,000 lbs., whereas a larger unit can weigh 20,000 lbs. or more. ?You will need a lowboy to move them,? Messinger says. ?That means you will have higher fixed costs to move the machine to the jobsite.

?The key in selecting any machine is doing as much as possible with a particular unit,? he continues. ?Any of these units will save on hand forming - and the more labor you can eliminate, the better your return.?

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