To avoid fracturing aggregates when compacting stone matrix asphalt (SMA) or open-graded mixes, it may be necessary to use two rollers set in low amplitude during the breakdown phase.

When it comes to mix-design optimization, two goals stand out: dollars to be saved and how sustainable a road you can build. This means doing your homework and understanding calculations in mix design, explains Shane Buchanan, asphalt performance manager with Oldcastle Materials Group’s Asphalt Performance Team. When designing a mix, it’s important to conduct a quick review of mix volumetrics “to make sure you know what you think you know,” he says. It also means, he adds, taking the time to ensure you are up to the current specifications in your area.

“It goes back to being too busy,” Buchanan points out. “You may not be aware of special provisions or specification changes. These could include changes from Departments of Transportation, a city or municipality, or even the Federal Aviation Administration. “Changes can open up the door to make a more economical mix,” Buchanan says. “If you are not aware of that, you are losing at the beginning of the process.”

Specification changes aren’t communicated as methodically as in the past when it resulted in a printed description in a specs book. “But with advancement of technology, specifications can change quite frequently,” Buchanan says. “It’s not always in printed form. This means you must constantly monitor an agency’s website.”

Buchanan also recommends that operations get involved with their local asphalt or stone association. “A lot of time, they help work with the agency to change or create new specifications,” he says. “It’s very important that you stayed tuned into the process.”

For example, the use of recycled asphalt pavement (RAP) and recycled asphalt shingles (RAS) in mixes is growing and changing very quickly. “It’s very dynamic,” Buchanan says. “You need to stay on top of what the state is allowing. If your understanding is that 15 percent can be RAP, but it was changed to a 25-percent allowance, you are leaving a lot of opportunity on the table.

“A lot of times when people are new to the industry, they are trained by someone else who was trained by someone else,” Buchanan says. Over time, training can get somewhat diluted. “People take leeway on concepts. If three steps removed from truth, you may not know exactly the correct way.”

Knowing the correct way is absolutely essential with volumetrics in mix design. “You need to understand the impact of aggregate grading on volumetrics, of asphalt grading on volumetrics,” Buchanan says. “The most critical volumetric property is VMA (voids in mineral aggregate).”

Before trying to just achieve volumetrics, Buchanan says, you need to understand what it means.

“Do not get caught in the trap of using formulas blindly,” he points out. “At least go back and work a volumetric phase diagram from start to finish so you can understand what all the phase components mean when tackling volumetrics. It is all related to mass and volume so there is just one way to do it correctly.”

This information is easily found online at the National Center for Asphalt Technology (NCAT), through the National Asphalt Pavement Association (NAPA) or even a state asphalt association, Buchanan says.

When you design the mix, Buchanan says, you need the minimum VMA. It can be equated to the extent of the mix. One of these components is liquid asphalt content.

Too much force and excessive rolling caused severe damage to aggregates and the surface of this asphalt layer.

Typically, during production, VMA is lost. “If you are designing with a VMA of 14.5, typically you are going to lose 0.5 to 0.7 percent of VMA during production,” Buchanan says. This is referred to as ‘VMA collapse.’ voids in mineral aggregate

“Because of VMA collapse with a minimum VMA requirement of 14.0, you may choose to design 14.5 to 14.7, based on your history or experience,” Buchanan notes. “Some states will pay on VMA during production, some will not. That also goes into the equation on the mix design side. If you’re not specifically paid on VMA during production, it may drive you in a different direction with regards to your design VMA.”

One key with VMA is paying attention to aggregate gravities and making sure they are accurate. Typically, accurate specific gravities are more easily obtained with coarse aggregates Buchanan says. With fine aggregate, you can have issue of getting the correct bulk specific gravity (Gsb) determined.”

The test method is such that materials with a lot of fines, such as minus-200, can give a misleading result. This can cause you to calculate a bulk gravity that is too low and an absorption that is too high. Relating that back to VMA, the bulk specific gravity of aggregate blend is a critical factor.

“If you are getting incorrect bulk specific gravity — if the gravity (is) too low — the result will be a slightly lower VMA calculated and you are directly penalizing yourself,” Buchanan says. “A 0.01 change in your bulk specific gravity is a 0.3 percent change in your VMA.”

When calculating aggregate gravities, Buchanan says, very close attention should be paid to aggregate absorption. “If at all possible, use the absolute lowest absorption possible,” Buchanan explains. “The higher the absorption, the more liquid asphalt will be absorbed in the stone so you are just wasting money. A good rule of thumb, if no other information is known, is that asphalt absorption will be about 50 percent of water absorption.”

Liquid asphalt price drives the mix cost, Buchanan says, so any measure that can be taken to optimize the mix with the amount of virgin liquid in the mix will directly correlate to an operation’s ability to make money. Every 0.1 percent of liquid asphalt binder has an impact of 55 cents per mix ton — with the assumption that virgin liquid is about $550 per ton. “That means every 0.1 percent of liquid you can save has an impact of 55 cents per mix ton,” Buchanan says. “That is a great deal of money.”

Capped products have essentially been “written off the books,” but using these products can also potentially reduce the bottom line mix by reducing aggregate cost, Buchanan explains.

This is applicable for externally or internally supplied products – for example, screenings and manufactured sand.

However, testing must be done to ensure capped product quality is present. These capped products are especially good for 9.5 or 4.5 mm mixes with higher P200 content, however, their use must be balanced with desired RAP use. RAP replaces fines at a 90-percent level. Fine-fractioned RAP replaces fine at a 100-percent level. A 100-percent replacement means that 1 percent of RAP directly replaces 1 percent of fines.

Buchanan notes that caution must be used when integrating these surplus or capped products into mixes.

“Make sure the materials work in the design, and make sure sufficient quantities exist for the jobs,” he says. “Do not be ‘guilted’ into using capped products, make sure their use is beneficial.”

But how should you determine what mixes to target for optimization?

Start by conducting an analysis of all produced mixes for the past year, Buchanan says. Then list mixes from top to bottom in terms of production volume.

“Most production will likely come from a relatively small number of mixes,” he says. “You might find that 10 percent of mixes yield 70 percent or more of the production. Make sure you focus time and available resources on critical mixes.”

To evaluate, use these formulas:

(1) Potential = (Opportunity) x (Volume) and

(2) Opportunity = f (specifications, material availability, margin potential, etc.).

“Do not overlook ‘specialty’ mixes such as SMA [stone-matrix asphalt], OGFC [open-graded friction courses], etc.,” Buchanan says. “You can never rest. Always remember, your competition is working when you are not.”

Aggregates impact density

When working with compaction crews, the asphalt manager needs to ensure the mix meets all the requirements to match production and get the required density to keep the mat smooth.

Part of achieving required density is knowing what kind of aggregate is in a mix and how it performs, explains Terry Humphrey, training consultant for Caterpillar Paving. When designing a mix, Humphrey suggests that it’s extremely important to know how the aggregate being used has performed in an L.A. Abrasion test. “This determines its durability – and durable aggregates stand up to traffic volume and axle loads over time,” he says. “This is an immediate opportunity to get required density right behind the paver. The team designing the road is concerned about these types of characteristics so it knows how the road will support loads over time.”

If there is good aggregate that has a low number in the L.A. Abrasion test there is confidence that density can be achieved without creating more air voids, Humphrey explains. “There is more risk for a contractor on poor density than anything else,” he says. “Poor density costs a lot of money. Having good rock helps you get full pay or a bonus. Aggregate quality is part of the puzzle.”

For example, on a highway project with high-traffic volume, local aggregate sources might not be good enough to handle the average daily traffic and high-axle loads. “You might have to haul in aggregate from 100 miles away,” Humphrey explains. “But if it’s a parking lot or a street with low volume, you have less concern and can user lower-quality aggregate.”

Granite is oftentimes considered more durable aggregate. However, slag from steel might be more durable, Humphrey points out. “Sedimentary rock, such as limestone, tends to be less durable – but there is a wide range.”

If the designers know the aggregate is durable, it also helps the design team determine the best amplitude, Humphrey adds. “Amplitude on a vibratory compactor determines the impact force that will be delivered onto the asphalt later,” he says. “The goal is to select the amplitude that is the highest amplitude the rock will accept without breaking or causing the drum to bounce. You don’t want the drum to bounce while it is working.”

If the road design team knows that if the rock is durable, it can focus efforts on other factors such as how thick the layer is and what is the maximum size aggregate to be used. “You need to have at least a 3-to-1 ratio of layer thickness to aggregate size,” Humphrey says. “Once you can check off that box, you need to ask whether the oil used in the binder is modified with polymers that make it thick.”

by Larry Walton, Associate Editor, ProPickup magazine

Other contractors take the same approach that I do to towing on ice behind a pickup: try to avoid it. But there are times when leaving the trailer at the shop is both impractical and bad for business, especially if your winter work involves snow control.

Most of the dirt movers we met on a tire test trip to Steamboat Springs, Colo., keep working until winter stops them. Agencies of course have snow control reponsibilites. So here, like any other place that is white and icy in the cold months, compact track loaders, backhoes, skid steers, patchers, plow blades, various attachments and other equipment have to be moved on trailers behind pickups.

So I was inspired to take a day of “snow tow” training at the Bridgestone Winter Driving School (BWDS) just outside of town to be better equipped to handle icy trailer towing.

Most of the winter driving tips and techniques I’ve learned on previous winter training classes at BWDS apply: Make sure the vehicle is in good working order; use snow tires; slow down; and do all your braking and accelerating in a straight line.

But the standard BWDS driving classes don’t teach one important thing: what to do during a “trailer event.” That’s where the snow-tow trailer towing class pays off big for a driver who’ll haul a trailer behing a pickup in deep winter.

I found this out the first time my instructor purposefully jackknifed the trailer behind the school’s specially equipped F-250 4×4 as we approached a 90-degree downhill right-hander on the trailering road course.

Instinctively, I went for a counter steer born of racing on mud tracks. Wrong.

The Bridgestone Winter Driving School designed a special trailer for snow-tow training behind the school’s F-250 4×4 diesel. The truck has a manual brake controller that is operated by the instructor from the passenger’s seat.
The trailer, loaded with several thousand pounds of water in a tank above the axles, is equipped with stabilizing cables on giant coil springs attached between the tongue and mid-frame. The system was designed by the school to limit the amount of jackknife on the pickup-trailer combination. This custom setup saves the tow vehicle from damage and helps students learn corrective driving skills quicker. –LW

My corrective steering action only served to fold the pickup-trailer combination even further.

Once I had the trailer back inline and the truck stopped, my instructor walked me through the correct response to such a trailer event: Accelerate to get the trailer back in line and then brake to regain control.

He also pointed out getting around corners with a trailer in icy conditions is best done by “boxing off” or “V-ing off” the corners. In other words, brake in a straight line before entering the corner, get all of the steering done at once while the trailer is responding, then accelerate out of the corner in a straight line.

We spent several hours going around the course again and again while he locked the trailer’s brakes and I practiced the cornering and recovery techniques. It wasn’t long before I could keep the trailer under control no matter how hard he tried to make it jackknife. I passed.

The beauty of training on an ice track is learning to control of pickup/trailer combination under safe, slow, controlled – but real – conditions with an expert in the passenger’s seat.

NOTE: There are also courses for drivers of trucks and cars without trailers.

Check out the school at www.winterdrive.com. Trailer classes set up by arrangement – email team@drivingsciences.com.

Don’t overlook these jobsite hazards when working near traffic.

By Lauren Heartsill Dowdle, Contributing Editor

When you work road construction zones there is never really a time to relax when it comes to safety. The job, more or less cordoned off from an ever-present public, demands safety awareness and so do the passing drivers. But when work halts, traffic doesn’t.

Each year, more than 20,000 workers are injured in road construction work zones, with 106 fatalities in 2010, according to the Federal Highway Administration (FHWA). Causes include (from most to least common) contact with objects or equipment; slips, trips or falls; overexertion, transportation incidents and exposure to harmful substances or environments.

Having jobs next to the motoring public is becoming even more common because a large portion of road projects are reconstruction, instead of new construction, putting crews on the sides and medians of busy streets and highways.

“When it’s a project that’s under traffic, crews need to take extra concern,” says Brian Turmail, executive director of public affairs, Associated General Contractors of America (AGC). “Being aware of cars driving in and out of the work zone can be a challenging situation for workers – making it important for the crews to know the speed limits around them.”

And if the constrained work area and extra element of dealing with cars doesn’t add enough pressure, the ever-present need to do more in less time constantly is in the front of everyone’s mind. To squeeze more into the workday, many crews are operating into and through the night to finish projects, which can limit visibility for them and drivers.

“It’s a balance,” Turmail says. “Safety should always come first – even though there’s a real emphasis on getting the jobs done quicker, which can bring up safety concerns.”

While most workers would know to enclose the work area with cones and put on reflective vests, there are some often-overlooked or downplayed situations that could quickly lead to injuries or fatalities on the jobsite. Here are six of those safety concerns to remember in road construction zones.

1 Don’t Stand Behind Trucks

A staple on road-construction project sites is the working truck. The traffic-control truck is especially common for Sterndahl Enterprises in Sun Valley, California. This full-service striping, stripe-removal and traffic-control company mostly works on reconstruction projects, making traffic safety a top concern, says Dennis “Chip” Sterndahl, president of Sterndahl Enterprises (www.sterndahl.com) and former president of the American Traffic Safety Services Association (ATSSA).

The acceptable processes, procedures, equipment and how his crews set up the equipment have evolved and improved in the past few years, Sterndahl says. One change they have made to minimize the possibility of injury is where the workers stand when they are near traffic-control equipment.

“History has shown many instances of employees picking up lane-closure signs who have been hit while standing at the back of the equipment,” Sterndahl says. “We try to avoid this by having workers stand to the side of the truck.”

The company welded the rear gates closed so no one can get the equipment off the truck from the back.

The National Institute for Occupational Safety and Health (NIOSH) reports 51 percent of worker-on-foot fatalities that occurred within a highway work zone involved backing vehicles, according to a federal government report. Emerging technologies in the field of operations include after-market devices, such as cameras and proximity detection systems. The use of spotters and internal traffic control plans can also make backing operations safer. Struck-by injuries and caught between injuries are two of the four leading causes of workplace fatalities. OSHA Integrated Management Information System (IMIS) data indicates that, between 2005 and 2010, more than 350 workers died as a result of backing incidents. While these incidents can be fatal, workers can also suffer severe, non-fatal injuries. A review of OSHA’s IMIS database found that backing incidents can result in serious injury to the back and pelvis, fractured bones, concussion, amputation and other injuries.

2 Don’t Be Complacent

On a jobsite that requires a rigid attention to detail, sometimes the simplest – and most important – safety practices can go overlooked. Many times, road crews forget to go back to the basics and become too comfortable when working around traffic.

“Something I commonly share in safety meetings – and perhaps the best advice – is to always use caution,” Sterndahl says. “Employees who have worked around high-speed traffic for many years almost get immune to it. This can create a dangerous situation if they become so used to it that they don’t practice caution.”

One way to counteract this complacency is for the jobsite managers to talk to their crews and prepare them for each jobsite and the dangers they could encounter.

Sterndahl has tailgate safety meetings specific to each jobsite, and they have companywide monthly safety meetings. New employees also receive jobsite and classroom training. “It creates a mindset in the new employee that they have an obligation to learn,” Sterndahl says. “By design, we’ve minimized the number of work-place injuries.”

Another factor in avoiding numbness to the job is for crews to remember where they are and to keep a watchful eye on the passing cars. Although it may sound simple, many accidents go back to this advice, Turmail says. “Beware of distracted drivers,” he says. “They’re dangerous anywhere, but when it comes to a work zone, they are even more dangerous.”

3 Barriers, Not Chairs

Often referred to as Jersey bumps, walls or k-rails, concrete barriers can be an effective way of separating workers from motorists or for re-routing traffic.

Sterndahl’s team has expanded their use of these fixed barriers wherever possible, and he urges others to do the same. “If the DOT will allow it, use more Jersey walls to keep traffic out of the work zone,” he says.

These sturdy dividers help direct drivers, and the same should be true for the crews. However, in some reported cases, workers have viewed these barriers as a place to relax, which can be a fatal mistake.

Sterndahl says he has heard of employees sitting on the protective barriers between the work area and traffic on their break. “That’s a classic mistake you wouldn’t your employees to make,” he says.

To help the barriers stand out even more along roadways, and serve as a reminder that they are not chairs, road crews can paint them a color that stands out from the background or install reflectors, lights or light tubes. These barriers can be effectively used in conjunction with other traffic-control devices such as warning signs to prevent drivers from getting too close.

4 Keep Communication Lines Open

If a rogue vehicle were to make its way into the work zone, it could obviously do a lot of damage and cause serious injuries. How information about ‘rogue’ dangers is relayed to the crew could save lives.

Sterndahl Enterprises installed two-way radios in their on- and off-highway vehicles for cases such as this one. “Having the two-way radios on the jobsite is critical,” he says. “It helps in the event that you need an early warning system. If a car breaches a lane closure, we can give everyone the heads up.”

On any road construction site, noise can make hearing and verbal communication difficult and at times impossible. If the jobsite equipment does not have radios, hand signals can help convey a command to an equipment operator and serve as a reminder of the workers whereabouts.

But lessons learned show that hand signals must be simple and clear and understood by everyone working the job.

5 Make Positive Contact

Equipment can be a major contributor to work-zone hazards. Add the extra physical constraints of working next to a roadway, and these machines account for 35 percent of the injuries, according to the FHWA.

“It’s important to be aware of the equipment around you,” Turmail says.

To keep from being struck by a piece of equipment, he suggests crews have spotters in place. In some cases, adding cameras to the equipment can also help with the operator’s blind spots. “Visibility is the issue within the work zone,” Turmail says.

The burden of responsibility to be on the lookout does not solely rest with the equipment operator, however. The crewmembers working on foot should also be aware of the machines around them.

Keeping these workers and equipment separated as much as possible can also limit injuries, according to the Centers for Disease Control’s (CDC) National Institute for Occupational Safety and Health (NIOSH).

“See and be seen: Don’t assume that just because an operator looks in your direction that he sees you,” Turmail warns. “Have positive contact with him, whether it’s hand signals or a nod.”

Most pieces of equipment have backup alarms as a safety feature, but there can still be accidents, especially with the added vehicle noise. Nearly half of road worker fatalities are caused from them being run over or backed over by vehicles or mobile equipment, according to the FHWA.

“A worker might think the alarm they hear is a machine 200 feet away, since there are so many alarms going off,” Turmail says. “It might not get their attention. They should constantly be aware of their working area.”

This attention to the area also applies when exiting the machine. “Don’t jump out or off of the equipment without checking the surroundings,” Sterndahl says. “Always be aware of the surroundings, including the motoring public and other equipment.”

There may be more injuries from the equipment on road project sites, Turmail says, but “if you get hit by a motorist, there’s less chance of survival.” So, he says it is important to be equally mindful of both.

6 Turn Down Lights at Night

As the sun goes down, visibility becomes an issue for workers and drivers alike. Both groups may be experiencing fatigue, also slowing down their response time. Setting up light towers is an effective move, but there are others.

Road crews chiefs should designate someone to make sure they are mindful of the traffic signs when it gets dark. They should set arrow panels at nighttime levels: Daytime settings that are used at night produce blinding light, which can affect motorists’ ability to see the road and work zone.

Crews should also reduce the spacing between any barriers or other channelizing devices to compensate for reduced driver visibility, according to the NIOSH.

When there are nighttime closures of two or more lanes on a freeway with three or more lanes of travel in the same direction, California road contractors, like Sterndahl, take advantage of the Construction Zone Enhanced Enforcement Program (COZEEP). This program allows the DOT to hire highway officers to patrol construction zones to reduce potential accidents. Other incidences when COZEEP would be used are when there are daytime or nighttime temporary closures of all lanes in the same direction of travel. Each road closure can be considered on a project-specific basis to see if COZEEP is needed.

Programs like this one and the continued emphasis on safety have steadily brought the number of injuries and fatalities down on road projects. Turmail says he’s hopeful this decrease is in part because of the workers’ and public’s awareness.

“It’s also reflective of the amount of miles driven going down because of gas prices and the recession,” he says.

Overall, highway fatalities declined 23 percent from 2002 to 2010, while work-zone fatalities declined 51 percent during that same amount of time, according to the FHWA.

“Safe practices are critical at all times,” Sterndahl says, “no matter if you’re working near traffic or on a building project.”

Mistakes Add Up in 2010

35%      Road-construction injuries caused by contact with objects or equipment

106          Workplace fatalities at road-construction sites

60%        Injury crashes between 6 a.m. to 9 p.m.

87,606  Crashes in work zones

– FHWA Work Zone Mobility and Safety Program’s data from 2010

Back to the Basics

After you and your crew have spotted some of the hidden hazards, it’s also important to remember the more-common safety practices.

• Always pay attention to the traffic, and never turn your back on it.

• Keep something, such as a barrier, between you and the road whenever possible. Don’t expose yourself to the traffic.

• Stay alert to any equipment changes.

• Wear the appropriate safety gear and high-visibility apparel: boots, gloves and vest.

• Designate a crewmember to keep the working area clear: An equipment operator who is concentrating on digging a hole might not be focused on the employees working around him.

• Assign a traffic-control supervisor to be responsible for the overall safety of the work-zone setup.

8 techniques for restoring concrete roads

By Lauren Heartsill Dowdle

Whether it’s patching a hairline crack or completely rebuilding an area with a crater-sized pothole, repairing concrete roads early on can minimize future damage and the time required for the job.

The repairer’s success with the work depends not only on the quality of the patching work itself but also on his pre-patching assessment and choice of solution. Figuring out the cause of the pavement deterioration can help determine what type of repair is best suited for the project.

“Know what kind of repair you need to make and then follow through with it,” says Dale Harrington, senior principal engineer, Snyder and Associates/National Concrete Pavement Technology Center. “You can’t just jump into it.”

If a crack occurs while working on a current project, it may be easier for the crew to diagnose the problem by retracing their steps. Was there a sudden change in the temperature? Did it rain? Did they forget to cover the surface? Or, was there a change in materials, saw timing or subgrade with the cracked section? Volume changing, restraint, curling, warping, strength, stiffness, base condition and early loadings are also factors that can cause early stage cracking.

It’s possible for concrete to go 20 to 30 years without needing any renovation, so for existing pavement, the direct cause may be unknown – it could, for example, range from load-associated issues to long-term drying shrinkage. But no matter the reason, the road deterioration symptoms are universal. Once diagnosed, the repairer can set a plan of action.

In many jobs, the deterioration will require a combination of techniques to become a smooth, sturdy pavement. Knowing what signs to look for and how to best treat the area will help road contractors achieve the best long-term results. “The types of repairs range from slab stabilization to joint-crack resealing,” Harrington says. “If multiple repairs are required, the sequence of applications needs to be understood and followed.”

Let’s dicuss eight popular types of concrete repair.

1. Full-Depth Repair

For major distress pavement areas, full-depth repairs can provide quality performance for 10 to 15 years if crews use the right materials. These repairs normally consist of cast-in-place concrete that replaces the full depth of the existing slab, or at least a portion of a slab to the bottom of the concrete.

For a smooth riding surface, repairs needs to made precisely with an understanding of any post-repair needs. For example, allowing for grinding and/or grooving, which can leave a “like new” surface.

This technique can be used where utility cuts are needed in the roadway, to restore problem areas at airports or at deteriorated cracks and joints on highways.

One of the most common types, full-depth repairs are usually a full lane-width wide, say12 feet, and 4 to 6 feet long, says the American Concrete Pavement Association.

Key techniques for effective full-depth repairs include having adequate working room (a minimum of 6 feet longitudinally), a uniform/stable platform, full-depth perimeter saw cuts, a longitudinal strike-off and being prepared for changes. The success of this repair also depends on installing it at the proper time with the right design.

If the slab could disintegrate when lifting it, crews should remove the patch area with a backhoe, angle the lift pins, position the cables and keep the lift height to a minimum.

2. Partial-Depth Repair

When only a small area of deteriorated concrete needs to be removed and replaced, partial-depth repair may be the best option. This method is traditionally used where joint or crack deterioration is in the top third of the slab (if it extends below this, usually a full-depth repair is necessary), Harrington says.

There are three types of partial-depth repair: spot repair, long joint/crack repair and bottom-half repair. Ranging from 10 inches to 6 feet in length, spot repairs can be used where existing load-transfer devices are still functional. The saw-and-chip method is the most common, but milling is rising in popularity in some areas, according to Daniel Frentress, Frentress Enterprises.

With cracks longer than 6 feet, a long joint/crack repair would be best and is usually done with milling. Workers can use a small jackhammer for the rest of the patch where the mill can’t reach. If the deterioration spreads to the full depth at a short distance, a bottom-half repair can be used on the edges or cross-joint locations that are not longer than 18 inches.

Steps for partial-depth repair include determining the repair boundaries, removing the concrete, preparing the area by sandblasting or air blasting, placing a strip of polystyrene or polyethylene compressible material in the joint, coating it with grout, adding patch material, applying curing compound and, finally, sealing the joint.

3. Stitching

Longitudinal cracks that are in a moderate or fair condition can be repaired with cross-stitching or slot-stitching. With these methods, crews use tie bars to stop the crack from widening vertically and horizontally. Cross-stitching creates a less-exposed surface area and is less intrusive to the slab, compared to slot-stitching. Neither method is intended for severely deteriorated or transverse cracks.

If contractors stitch a transverse crack that serves as an adjacent joint, the stitching will not allow the transverse joint to move. This can cause a new crack to form near the stitched working crack. The concrete may also spall over the reinforcing bars. For less-deteriorated cracks, sealing and maintaining the crack may be enough to repair the road.

4. Joint Sealing

Well-constructed joints can prevent random cracks and prevent faulting, so repairing them is important for the overall road success. “Concrete repairs have a lot to do with joints,” Harrington says.

Sealing joints leads to proper joint expansion and contraction and can reduce moisture amounts. This technique also prevents the intrusion of incompressible materials that can cause pressure-related distress such as spalling, buckling and slab shattering.

What material the road contractor selects should be based on their experience level, the traffic level, crack characteristics, climate conditions and cost concerns.

Crews should only place joint sealer when the surface is dry. The sealer is sensitive to temperature, so crews should place it when the pavement and temperature is 40 degrees Fahrenheit or higher.

If the poured joint sealant does not adhere, water or materials can enter the joint and cause poor performance. Problems can also arise if there are poor sealant properties due to over/under heating, the sealant is not sized properly or the joint is too wide.

5. Slab Stabilization

If repairers choose slab stabilization (undersealing) as the mode for repair, they should make sure the joints and working cracks have lost support. If this is not the case, the stabilization is not only wasteful; it could also damage the pavement’s performance.

Depending on the severity of the distressed, cracked pavement, concrete repairs can range from slab stabilization to the least-invasive type, joint and crack resealing.

For the best results, the stabilization must be performed prior to the onset of pavement damage due to support loss. However, it is important to address the underlying mechanisms, as well, to provide long-term results. Crews should use materials that can penetrate into thin voids, while being strong and durable enough to withstand external pressures.

Another issue to be on the watch out for with this type of repair is the ability to identify voids underneath the slab. If crews perform stabilization where there is no void, pumping material beneath the slab can cause stress points and increase the concrete’s deterioration.

6. Slab Jacking

Slab jacking differs in that it consists of the pressure insertion of a grout material beneath the slab to slowly raise the slab until it has a smooth profile.

With this method, it is important for the crew to monitor the amount of lift being performed. The slab should not be lifted more than 1/4 inch at a time to cut down on excessive stress. Materials used for slab jacking, such as cement grout and polyurethanes, are normally stiffer than those for stabilization.

7. Dowel Bar Retrofit

A mode of reinforcing cracks in pavement, dowel bar retrofit (DBR) consists of inserting steel dowel bars in slots that are cut across the cracks. It is important that the slots do not cross over any parallel cracks.

To prevent corner cracking from slots cut too deep or patching-material failure, crews should measure the dowel bar retrofit assembly height to guarantee proper saw-cut depth. The dowel-bar-slot width must also be checked to make sure the chairs and foam core board fit comfortably within the sides of the slot.

Crews should remove the existing concrete from the slot using jackhammers weighing 30 pounds or less, and the jackhammer should be operated at a 45-degree angle or less, says the Washington State Department of Transportation. If held in a vertical position, the jackhammer could go through the bottom of the slot.

When the dowel bar slots are finished, workers need to make sure all of the water and debris are removed before they add the patching materials. Transverse joints and cracks must be caulked with the slot, and the caulking material must extend more than 1/2 inch on either side of the joint or crack.

The dowel bars should be coated with a parting compound before being placed in the slot. To prevent the dowel bar from moving, crews should place the patching material adjacent to the bar, instead of dumping it directly, and spread it toward the slot.

Overworking the patching material during the finishing project can cause segregation and floating of the fine material to the surface of the slot, so crews should leave the material 1/8- to 1/4-inch high. The excess material will be removed during the diamond-grinding process.

8. Diamond Grinding

To smooth bumps, restore friction and reduce tire-pavement noise, workers can turn to diamond grinding. This technique produces grooves and lands in the pavement to correct irregularities such as roughness or faulting.

Structurally deficient pavements should not be ground without having major-distressed sections repaired, according to the Federal Highway Administration (FHWA). It needs to begin and end at lines normal to the pavement centerline and be longitudinal.

Road repair teams should consider the concrete aggregate type, grinding head and equipment size, reducing excessive vibrations and making sure the grinder bogie wheels are true (round). It is also important for them to make sure the match line between passes of the grinder doesn’t coincide with the wheel path, which could cause irregular grinding patterns.

Another aspect of diamond grinding that should be avoided is “holidays” – an unground area on the pavement surface.

To avoid these, crews should not lower the isolated low spots (holidays) that are less than 2.7 square feet, according to the ACPA. If the operation causes an unacceptable amount of holidays, they should lower the grinding head and make another pass.

The probability of a diamond-ground surface lasting eight years before needing another rehabilitation is 98 percent, according to the study The Longevity and Performance of Diamond-Ground Pavements by Sreenath Rao, Thomas Yu and Michael I. Darter in the Portland Cement Association Research and Development Bulletin RD 118.

What caused the cracks?

The problem: Road crews pour concrete pavement on a warm day in October. The temperature drops substantially in the afternoon, and the concrete is not covered. The next day, they see a 600-foot section of roadway has transverse cracks every 12 feet. The cracks occur about every second or third joint. There were no changes in materials, saw timing, the base or subgrade with this section.

What happened: Concrete expands as the temperature rises and contracts as it falls, which can cause early-age cracking when the top of the slab is considerably colder than the bottom of the slab. In this case, there was a sharp drop in the temperature when the concrete was at its warmest. The pavement was expanding during the concrete hydration and heat of the day. After the cold front moved in during the night, the top of the newly poured section was cooling following the final setting. The differential temperature in the concrete from the top to bottom caused movement. This resulted in stress building up in the new section that was greater than its strength, causing the cracks.

The solution: They should have kept the pavement covered for the first night to prevent substantial temperature change throughout the depth of the new pavement. It is also important to saw the joints as soon as possible with an early-entry saw to relieve the stress. When tying lanes, road contractors may also need to start paving later in the day when it is not as hot.

Source: Iowa Department of Transportation, Dale Harrington

Creating mixtures for smoothness and low noise

By Lauren Heartsill Dowdle

Grinding, loud, uneven roads can leave drivers and their vehicles shaken up after a long ride. So it’s no surprise that road conditions are the public’s No. 1 criterion for satisfaction, according to a 2002 Federal Highway Administration (FHWA) survey.

“Noise can affect the passengers in a vehicle, as well as the people living and working along a road,” says Trenton Clark, director of engineering, Virginia Asphalt Association (VAA), in Richmond, Va. “The owner should keep that in mind when specifying a treatment for a roadway – either new construction or resurfacing. It is a balance between managing costs and benefits.”

And although a road project’s checklist might not include the end-user’s approval, smoothness standards and specifications continue to be an important part of many road builders’ contracts and planning stages.

“Several factors go into achieving a smooth ride: mix design, mix delivery to the project, proper paver operation and compaction,” Clark says.

But eliminating bumps is not the only, or main, benefit of laying an even surface – a National Cooperative Highway Research Program analysis shows improved smoothness extends pavement performance life by up to 50 percent.

“Transportation agencies have a goal to provide the lowest lifecycle cost for road treatment,” says Jim Barnat, vice president of innovation, Road Science, a division of ArrMaz. “As secondary considerations, these agencies look at aesthetics, ride quality and quietness characteristics. They generally focus on durable pavement structures and crack-resistant surfaces, providing the best return on their investment.”

On the road to create lasting, smooth surfaces, some have stopped to address noise concerns, as well. These departments of transportation, including those in Arizona, Florida, Minnesota and Kansas, have tested pavement alternatives by using rubberized-asphalt mixtures near residential and sound-sensitive areas to decrease the traffic noise.

“Road noise is generated from two main sources – a vehicle’s engine/drive train and the tire-pavement interaction,” Clark says.

Virginia roadbuilders conducted an experiment with various surface mixes and aggregate sizes with the goal of discovering which materials created quieter, yet smooth, roads.

The Experiment

When a bill was introduced in Virgina in 2011 to develop quiet-pavement technologies to aid in sound mitigation, the Virginia Department of Transportation (VDOT) constructed road demonstrations to test various surface mixtures.

VDOT and its asphalt industry partner, the VAA, created noise-reducing surface mixes to be used on the projects, with each site including a control section and three experimental sections.

“When rubber can be used to reduce the overall cost of the asphalt mix and provide equal or superior performance, then rubber should be used.” Trenton Clark, director of engineering, Virginia Asphalt Association (VAA)

The quiet pavement project on State Route 7 went to Superior Paving, and Branscome won the remaining two sites – one west of Williamsburg on State Road 199 and another on State Road 288.

The control section was SMA-9.5 with PG 76-22 laid at 1 1⁄2 inches. The first experimental section used a porous friction course (PFC) with a 9.5-millimeter nominal maximum aggregate size (PG 70-28 polymer modified binder) as one section (1-inch application).

For another section, VDOT specified a PFC with a 12.5-millimeter maximum nominal aggregate size and PG 70-28 binder. The larger aggregate size and an application thickness of two inches were selected to improve drainage characteristics and promote a void structure that might support longer-term noise reduction, Clark says. “The best way to make a pavement quiet is the surface texture and porosity.”

They used a PFC-9.5 with a rubber-modified binder for the last experimental section to explore the noise-reducing attributes of rubber. This binder met the requirements of a PG 82-22 with a minimum of 10-percent ground-tire rubber by weight of asphalt binder.

While the polymer-modified binder and aggregate were provided from different sources, all of the rubber-modified binder came from Blacklidge Emulsions in Gulfport, Miss. This binder was introduced to the mix through specialized tanker equipped with an agitator.

“We had to make some very minor adjustments to the plant to accommodate this procedure [pumping from an agitator tank], and it worked great,” says David White, general manager, Superior Paving.

Depending on the project, the crews used either a new surface (one placed in the last year or two) or placed a binder layer of asphalt prior to laying the final surface for the quiet pavement sections. For two of the projects, the existing surface was removed through milling to maintain or improve cross sections.

Both companies used a trackless tack-coat material and a standard paver, and the paving procedures were slightly modified based on the application thickness. For their rolling operations, they did four passes with a 10-ton static roller with no density requirement.

After all three projects were completed, VDOT performed noise, ride-quality and friction testing. Their initial tests showed both Superior Paving and Branscome were able to provide a smooth, quiet and skid-resistant surface. The rubber-modified PFC-9.5 and the PFC-12.5 were the quietest surfaces, and both had an average decibel reading of approximately 98 to 98.5.

“For the sections installed with rubber, the final ride quality was as good as the sections without rubber,” Clark says. “For a few sections, the ride quality was better.” However, he doubts there’s a statistical difference between the two and says the road condition under the pavement materials may have also played a factor.

The PFC-9.5 with PG 70-28 was slightly higher with an average reading of 99.6 decibels. The ride quality and wet-skid resistance on all of these sections were excellent, he says.

“Given this surprising outcome and the expectation of lower noise levels using rubber, VDOT has installed rubber-modified PFC-12.5 on a section of the Fairfax County Parkway in 2012, as well as a section on the NCAT Test Track,” Clark says.

But every project and choice of materials and mixes boils down to a dollar amount, and Clarks says the use of rubber or other asphalt mixes should be based on the best economic value and benefit for the owner.

“When rubber can be used to reduce the overall cost of the asphalt mix and provide equal or superior performance, then rubber should be used,” Clark says. “The biggest bang for the buck will be in dense graded and gap graded (i.e., stone matrix asphalt) mixes. However, unless the use of rubber-modified binders is permitted by an owner/transportation agency or specified in the contract, then the overall use will be minimal.”

For 2012, VDOT plans to construct additional experimental sections in Virginia and at the NCAT test track. These mixes, which will include a PFC-9.5, a SMA-9.5 and a SMA-12.5, will also use the rubber-modified asphalt binder. Future testing will monitor changes in noise, ride, skid resistance and crack resistance, Clark says.

Let the jobsite be the judge

By Lauren Heartsill Dowdle

In the battle between choosing tires or tracks, buyers should let their projects cast the determining vote on which would be the best fit for their fleet.

“The most important consideration for a contractor is going to be the primary type of work he does,” says Mike Fitzgerald, loader product specialist, Bobcat.

The compact track loader market gained ground in the past decade – with many roadbuilders valuing productivity over initial cost – but there’s been a shift back toward skid-steer loaders since the 2008 economic downturn, says Jamie Wright, product manager, Terex Construction Americas. He estimates CTLs make up between 20 and 25 percent of the market, while SSLs hold between 75 and 80 percent, according to our sister publication, Equipment World.

“The compact-track loader trend started as a result of contractors wanting to get jobs done faster, no matter the acquisition costs or operational cost of the unit,” Wright continues. “With the economic downturn, contractors were more selective and looking for ways to manage their equipment inventories more efficiently. As part of this, they are adding skid-steer loaders back into their fleet since they are able to accomplish many of the same tasks at a lower operating expense.”

The most important consideration for a roadbuilder is his primary type of work.

So when does the price tag equal the benefits, and how can roadbuilders know which one they need for their next project? Here’s what the experts have to say.

Jobsite Checklist

When deciding between a wheeled or tracked machine, owners should first picture how the equipment would be used in their work. Categorizing job types, such as new or existing construction, dry or muddy conditions and traveling distances on the jobsite, can reveal how equipment is currently being used and what features the equipment will need to be profitable and efficient.

If a job requires extra traction for pushing into piles on soft or muddy ground, a tracked piece of equipment would be ideal because the tracks have more area in contact with the surface, which make them better for dozing and digging jobs. Tracked machines are also good for new-construction projects where there are no improved surfaces.

“For the best all-around mobility and for working longer seasons in wet or muddy conditions, compact-track loaders offer superior flotation, traction and the least amount of turf impact or damage,” says Tim O’Brien, brand marketing manager, Case Construction Equipment. “CTLs also have a more stable and consistent platform for grading applications but have a slower overall top travel speed.”

With ground conditions varying around the country, the choice between tracks or wheels can also depend on the job’s location. In some regions, tracked equipment is more prominent than others and can also extend the typical contractor’s working year because of its ability to float on wet ground.

“In areas like the Southwest where the ground is always dry and hard, you will have a hard time finding someone who owns a CTL,” Fitzgerald says. “Whereas, in the Midwest where the ground is clay or sand and conditions can vary by the weather, many contractors own both.” He advises contractors to talk to a local dealer who sells CTLs to get an idea of how long the machine extends the work year in that area.

If most of your projects will be on improved surfaces or in an existing development, a wheeled machine would be best because the tires wear less quickly than tracks on paved surfaces. Concrete and asphalt applications, traveling significant distances on a jobsite and some winter jobs will also call for wheeled machines.

“Skid steers tend to be better for scraping and snow plowing tasks that require the tires to penetrate mud, muck or snow to get down to a firmer traction surface,” O’Brien says.

For working on surfaces where tire punctures can become a problem, you could also consider buying a set of poly-fill tires. “This will eliminate the downtime associated with a flat tire while maintaining the ride characteristics of a pneumatic tire,” Fitzgerald says.

Cost Comparison

The biggest deterrent for many contractors with a tracked machine is the dollar amount, something manufacturers have tried to combat with longer track life, performance increases and undercarriage suspension systems for smoother rides. Figuring out the breaking point between productivity and cost for both the tire and track is key when choosing between the two.

Skid-steer loaders have a lower initial cost for the same size machine and lower owning-and-operating costs because the tires cost far less than the rubber tracks. A set of skid-steer tires can cost between $600 and $1,000 and last 600 to 1,000 hours. Rubber tracks cost $3,000 to $4,500 per set and last 1,200 to 1,600 hours. With proper operation of the loader, rubber tracks should last about twice as long as tires. However, tires still cost considerably less than tracks, Fitzgerald says.

Overall, tracks are more expensive to maintain than wheels, so the cost of the equipment can also come into play,” he says.

Although tire costs for skid steers are often lower than the hourly cost of tracks for CTLs, the downtime and risk of downtime to replace tires or fix flats is greater with skid steers. That is why many high-production applications have moved to using only solid tires for their skid steers.

“The most important maintenance cost item on either is rubber – tires for skid steers and tracks for compact track loaders,” O’Brien says. “Generally, the cost of keeping the machine fitted with tracks is more than with skid steers, but it depends on the applications, underfoot surfaces and especially operator techniques that will impact these costs.” (See “Reduce Downtime” sidebar for proper operation and maintenance techniques.)

Wright says a CTL can pay for itself in as little as 18 months, if all goes well. “Don’t sacrifice just to save a dollar,” Wright tells Equipment World. “Always buy quality; a loader and attachment need to be durable and reliable because downtime is expensive. Be sure to select equipment that makes the most sense for the applications it’ll be used in.” He recommends customers choose a machine that will equate to 85 or 90 percent of their needs.

Best of Both Worlds

For skid steer owners who occasionally work in rough, rocky or muddy conditions, a set of over-the-tire tracks may be an alternative to purchasing or renting a compact-track loader.

“Skid-steer loaders are better for mobility on hard or consistent surfaces but can be fitted with track chains temporarily for better flotation and mobility for muddy or wet surfaces, or to reduce damage to turf for landscaping or tree planting applications,” O’Brien says.

But operators will still want to be mindful of the type of surfaces they will be covering with the equipment. “Over-the-tire steel tracks can add productivity to existing equipment, but they can also damage sidewalks and curbs,” Fitzgerald says. “You want to use rubber tracks in areas under development, which have improved surfaces, and use steel tracks in areas that are primarily dirt or new construction.”

Tracks can typically be installed in 30 minutes and removed in about 10 minutes. They range in price from $2,500 to $5,000 depending on the machine model, track width and length.

Make a Decision

With each having its pros and cons, it is important for roadbuilders to understand their project needs before deciding between wheeled or tracked equipment. There might not be a universally correct choice, but there is a right one for each contractor’s services.

And although the industry as a whole currently is leaning more toward the lower price of tires, the verdict is still out on whether the tracked-equipment market will ever equal or surpass wheeled machines. “As the construction industry continues to recover, compact-track loaders could again become as popular as skid-steer loaders because their productivity is incredible,” Wright says to Equipment World.

REDUCE DOWNTIME

Your equipment won’t get far without functional tires or tracks, so here are some maintenance tips to keeping them rolling.

• Perform visual inspections of undercarriage components. Most manufacturers’ idlers and rollers are permanently sealed and lubricated; however, they — along with sprockets and tracks — may need to be replaced periodically depending on a machine’s use.

• Train operators. With the proper instruction, your crew can help reduce costs from worn tires and tracks. For example, teaching CTL operators to find ways to minimize turns or make them less abruptly or on softer surfaces will greatly reduce expensive track wear: Three-point turns, rather than spinning or counter-rotating, will help save on undercarriage wear. And training operators to clean out the undercarriage at the end of every shift will cut maintenance costs, too.

• Keep repair tools handy. The occasional track tensioning can be done with a common grease gun, and tracks can be replaced in less than an hour on some machines. Handling maintenance issues on site can help reduce the overall cost and downtime.

Source: Mike Fitzgerald, Bobcat

OGFCs cut spray and can be very, very quiet.

For several years, a number of states have placed open-graded friction courses (OGFCs) as a wearing course on their high-volume, high-speed roadways.

An OGFC is a thin, permeable mix with high air voids and a relatively high asphalt content. These mixes are safer than dense-graded asphalt because they reduce splash and spray in wet weather, and they drastically lower the potential for hydroplaning because water drains into them and out to the side. Driver visibility is improved, and headlight glare is reduced.

But OGFCs are not recommended for low-volume, low-speed pavements. That’s because high-speed traffic actually helps maintain the benefits of OGFCs. The action of moving traffic cleans dust and other materials that can clog the mix and reduce its permeability and noise-reducing ability.

In the early 1970s, several Western states began placing plant mix seals in response to the Federal Highway Administration’s (FHWA) program to improve the frictional resistance of U.S. road surfaces. The aggregates typically had a top size of 9.5 mm to 12.5 mm (3/8 to 1/2 inch) and were mixed with a relatively high percentage of asphalt cement in a conventional asphalt plant. Mixes were placed at 15- to 20-mm thick (5/8- to ¾-inch).

Durability of these OGFC mixes, however, became a problem. They wore out quickly and raveled. The underlying asphalt in some pavements suffered from stripping. So in the 1980s, some states placed a moratorium on the use of OGFCs. But a handful of states – Georgia, Oregon and Texas among them – saw the potential of OGFCs and set about improving the mix.

FHWA encouraged the improvement efforts. States began to add both polymer-modified asphalts and fibers to the mix to prevent drain-down. The combination of polymers and fibers stabilized the mixtures. It became easier to produce OGFCs because the mixes were less sensitive to mixing plant temperature variations and could be produced at more conventional operating temperatures. State agencies boosted the asphalt content and the air voids in OGFCs, and they specified a high percentage of polish-resistant, crushed aggregate.

The modified asphalts created a thicker film on the OGFC aggregates, so raveling and oxidation were reduced. Durability increased because of the increased asphalt content and polymer modification.

“We made a trip to Georgia to see what they [Georgia DOT] were doing right,” Dale Rand, flexible pavements branch director for the Texas Department of Transportation (TxDOT), tells Better Roads. “[Georgia had] added cellulose fibers and mineral fibers and polymers to make the mixes more durable. Georgia had started placing [its] improved mixes in the early 1990s and they were seven to eight years old by the time we saw them. So we came back and tweaked our design somewhat and came up with our version, which is very similar to the Georgia version. We just call it Permeable Friction Course (PFC).”

For the PFCs, Rand says Texas now uses PG 76-22 asphalt cement – polymer modified – and typically 0.3 percent of cellulose fibers. Some 80 to 100 percent of the aggregate passes the 1/2-inch sieve and 35 to 60 percent passes the 3/8-inch sieve. A minimum of 6 percent asphalt is required in Texas PFCs, and they are designed to have about 20-percent air voids, Rand says.

“We typically specify them on roadways that have a history of wet weather accidents,” Rand points out. “In my opinion, they are most beneficial on undivided highways where you have a history of wet weather accidents. Our TxDOT official policy is that we target pavements in areas to prevent wet weather accidents. We also use a number of PFCs routinely on our Interstate system. We use them on high-speed facilities, if the posted speed limit is above 45 mph.”

Rand says PFC mixes cost about 20 percent more per ton than conventional dense-graded mixes. But because the PFCs have 20 percent air voids in them vs. 7 percent in dense-graded mixes, the cost per square yard of the PFCs is roughly equivalent to the dense-graded mixes. Typically, Rand says, TxDOT applies the PFCs at 1-1/4 inches thick to 1-1/2 inches thick, with 1-1/4 inches as the typical thickness.

Georgia’s Experience

The Georgia DOT uses not one, but three versions of open-graded surface mixtures. One is a conventional OGFC, designed with 18 percent air voids. Another is a porous European mix (PEM), featuring even higher air voids, at 24 percent, and a 12.5-mm top size aggregate. “Our specification calls for PEM on all Interstates that have an asphalt surface,” says Peter Wu, assistant state materials engineer.

The third open-graded mix is a 9.5 mm (3/8 inch) nominal maximum aggregate size OGFC. “That is for limited use on state routes with a specific drainage problem,” Wu says.

Georgia’s regular OGFC is a 12.5-mm mix with a target asphalt content of 6 percent. The PEM, with higher air voids, is designed to drain water more quickly than the regular OGFC. Georgia applies the PEM at 135 pounds per square yard. “The higher air voids give it more room to drain water off,” says Wu. The 135 pounds is equivalent to 1.25 inches.

Both Georgia’s PEM and the OGFC use PG 76-22 polymer modified asphalt cement. Typically cellulose fibers at 0.3 percent by weight are specified, and if mineral fibers are used, their weight is 0.4 percent. Wu says in Georgia crumb rubber is under consideration in lieu of polymer modified asphalt.

European Experience

After OGFC was developed in the United States in the early 1970s, it has been used extensively in many European countries, according to IS 115, a technical document known as Design, Construction, and Maintenance of Open-Graded Friction Courses and published by the National Asphalt Pavement Association (NAPA). The document says porous asphalt, as it is called in Europe, has been used frequently in Germany, the Netherlands, France, Italy, United Kingdom, Belgium, Spain, Switzerland and Austria.

However, unlike the OGFC mixes that didn’t work very well in the United States in the 1970s, porous asphalt in Europe evolved with a coarser gradation of aggregates, and higher in-place air voids – 17 to 22 percent. That gave the mixes higher permeability, and European countries generally place them in thicknesses up to 2 inches. Nominal maximum aggregate sizes ranged from 11 mm, or 7/16 inch, up to 16 mm, or 5/8 inch.

Polymer-modified binders or fibers, or sometimes both, are used in the European mixes to obtain thick and strong binder films for maximum resistance to aging and raveling. OGFC is used in Europe in a full range of climates, from hot and dry to cold and wet.

Whispering Asphalt

Tires rolling on the road force air away in front of the tire, and suck air in behind the area of contact between the tire and the road. This air pumping generates high-frequency noise, according to the NAPA document. But with OGFC, the pumping, and therefore the noise, is reduced because air is pumped down into the porous pavement. Porous OGFC also reduces noise by absorbing some of the noise emitted by vehicles. On dense surfaces, the noise emitted towards the pavement is reflected to the surroundings.

Because of its noise-reducing ability, OGFC is known in Germany as “Fliisterasphalt,” or whispering asphalt. Full-scale trial sections of OGFC on German motorways and trunk roads between 1986 and 1990 measured reductions in rolling noise of up to 6 decibels(dBA), and this value has since been adopted as the basis for calculating the noise-reducing properties of OGFC.

NAPA does not recommend applying a dense-graded asphalt to an OGFC at the end of its service life. Studies have found that the overlay will trap water in the OGFC and cause the pavement to deteriorate. Generally, it is recommended to mill off the existing OGFC prior to replacing it with a new OGFC or any other wearing course.

Fixing ‘Dead Man’s Curve’

The Texas Department of Transportation (TxDOT) has a notable success story to tell about its permeable friction courses (PFCs). In the late 1990s, a 2-mile section of RM 1431 near Jonestown, Texas, in the Austin District, came to be called “Dead Man’s Curve” by the media and local residents. For years, the Austin District took proactive measures to reduce the number of accidents along RM 1431, but the rate of wet weather accidents remained unchanged.

So TxDOT placed a PFC on RM 1431 under an emergency contract to address the number of wet weather accidents and fatalities. It worked. The number of wet weather accidents on this highway dropped by 93 percent in the four years since placement of the mix in February 2004, compared to the three-year period prior to the placement of the overlay.

For fleet managers, it’s time to prep for winter.

While everyone else is having summer fun and worrying about sunblock, savvy fleet managers are getting their trucks, equipment, and parts inventories ready for winters. They know if they don’t, they can get caught out.

Bridgestone Winter Driving School managers follow their own advice on winter prep, equipping their pickups with dedicated snow tires for plowing miles of roads outside of Colorado Springs, Colo.

Transitioning between seasons, especially from summer to winter, isn’t an easy task because the working conditions and stresses put on equipment vary so much with the elements. When it comes to setting up a fleet’s pickups and heavy-duty trucks for winter duty, there are some major routine moves to make. But it’s shocking how often some of them get overlooked. And that’s downright dangerous.

I bleed pickups, but here I’m talking everything from half-ton to Class 8 trucks that have to work for you in the dead of winter.

TIRES

No, the “M&S” and “all-season” bargain treads don’t make good winter tires. Neither do mud tires. If winter traction and driver safety are paramount, equip the fleet with dedicated winter tires such as Bridgestone’s Blizzak W965s, Nokian Hakkapeliitta LTs or Goodyear Ultra Grip Ice WRTs. There’s no comparison to the level of vehicle control gained by switching to purpose-built snow/ice tires when winter arrives. To extend their life, switch back to the summer treads when spring arrives.

SNOWPLOWS

All snowplows are not created equal, especially when it comes to those for use on pickups. The newest generations have better moldboard trip mechanisms to keep encounters with curbs and manhole covers from tearing up the plow and the truck and other advances to make old timers shake their heads. To be winter-ready make sure your plow and truck linkages will work in a hurry, that plows and trucks match and that the plow does what you think it will do.

AUTO TRANSMISSIONS

Automatic transmissions take the biggest hit during the winter, especially if the truck is used for plowing. The speeds are low, but the load put on the transmission is high. This means it’s critical to service the transmission, change the external filter, check the fluid to make sure it’s in good condition and inspect the transmisson cooler lines. All it takes to fry an automatic is one overheat scenario.

ENGINE COOLANT

Even though it’s winter, engine temps can be high because snow and ice can block good airflow to the radiator. It’s all the more important that the radiator coolant be in good condition (red/pink color) and water and antifreeze are mixed 50/50. A higher mix percentage of antifreeze hurts cooling.

WINDSHIELD WIPERS

Driver safety begins with a clean windshield, which provides that extra second or two to react. A clean windshield also reduces driver fatigue. Everblades heated wipers are excellent in winter, and the silicone-impregnated versions from Rain-X, PIAA, Tripledge, ArmorAll and SilBlade are good choices. Silicone blades clean better than conventional wipers and they treat the windshield at the same time. Silicone-impregnated wipers also last longer than conventional wipers — especially when subjected to road salts and sand.

SHOCKS

The typical OEM shocks are worn out by the time they have 15,000 miles on them, and the typical high-pressure gas shocks should be replaced with high-pressure gas version after about 40,000 miles. Bad shocks lead to handling issues in the winter— especially when plows and spreaders are installed. So let mileage be your replacement indicator for shocks.

FRONT AXLES

Pay close attention to the boots and tie-rod ends of GM 4x4s; torn CV boots need to be replaced to keep sand and salt from getting into the joints. This is the time to replace the OE outer tie-rod ends of 4×4 diesels with heavy-duty replacements like those offered by Cognito Motorsports. It’s also a good time to check gear oil and replace it if there’s any hint of water in the lube.

WARNING LIGHTS

Safety and visibility go hand in hand. It’s never too late to add a few more high-intensity LED flashers to the truck. A couple of the super mini-LEDs mounted on the headache rack or the front and rear fenders can dramatically improve visibility without a big expense. Whelen and Buyer’s Products are just a few manufacturers that offer the min LEDs.

ENGINE OIL

Winter prep should include switching to “zero-weight” engine oils. These synthetics, such as those from Royal Purple, Mobil Delvac and Pennzoil, provide the lubrication needed when hot, yet keep the engine components protected at cold startup. They can also improve fuel economy.

DISC BRAKES

Stopping power is not only dependent on good tires, it’s how well the brakes work. When water, ice and snow are key elements on the road or jobsite, rotors with slots provide better cleaning and drying performance than smooth OEM versions. Higher quality pads also benefit work pickups. Stainless Steel Brakes Corp (SSBC), Disc Brakes of Australia (DBA) and EBC Brakes have special pickup disc brake upgrade packages with rotors and pads.

HID HEADLIGHTS

Good night vision is dependent on the quality of headlights. Replacing stock OE halogen bulbs with HID Xenons can dramatically improve pickup headlight performance without affecting oncoming traffic (when properly adjusted.) PIAA, Phillips and Oracle Lighting Products offer good kits. Choose an HID kit in the 6,000K range for optimum results.

Editor’s Note: This story was especially written for Better Roads by Bruce Smith, editor of our sister publication ProPickup magazine.

Recycled asphalt shingles are an acquired taste

When going from the roof to the road in recycled asphalt pavement (RAP) mixes, “it’s all in the details,” says John Christensen, technical marketing manager for MeadWestvaco (MWV).

It’s not impossible to get density in RAP mixes incorporating recycled asphalt shingles (RAS), “but it helps to pay a little more attention to details. It’s definitely a more difficult mix to work with once you put shingles in there.”

But agencies and contractors are able to save money on virgin asphalt by using RAS. “This is what pushes a lot of contractors to use [RAS] now that it’s about $600 per liquid ton for asphalt,” Christensen says.

“When I first started working with contractors, RAP was a ‘four letter word,’” Christensen says. “It was a waste material that was usually given away or used by state or local DOTs who retained ownership. If it was used, it wasn’t more than 10 percent. It was easier to just use virgin asphalt and not deal with the headaches of the inconsistencies caused by putting RAP in a mix, because virgin asphalt was cheap and readily available. Those days are gone. Liquid asphalt is not cheap anymore, and sometimes it’s not as readily available and many specifications would not allow more than 10 percent – if any at all .”

RAS has provided an environmentally responsible option, and its economy is added-value for agencies, says Steve Jackson, P.E., quality control manager of Missouri-based NB West. But like Christensen says, Jackson notes that RAS must be dealt with carefully to ensure it will meet specs and perform well.

Jackson says he is seeing RAP mixes in early spring and in late fall, when temperatures aren’t as hot. In the summer, more shingle mixes are being used. “When temperatures get below 40 degrees F, people look at not using shingle mixes or [contractors] using ones with 6 to 7 percent going down to 2 to 3 percent because [the mixes] are getting stiffer,” Jackson says. “In spring and late fall, it’s wetter so it’s harder to dry them.” Jackson suggests keeping the shingles under a tarp or in a storage building to help deter moisture.

But there’s more to using recycled asphalt shingles than just keeping them dry. “You have to determine the specific gravity for your mix design,” Jackson says. This can get tricky because different states use different methods. Missouri uses the effective specific gravity as the value for the bulk-specific gravity to determine the voids in the mineral aggregate (VMA). This is just one method that may be used for VMA calculation.

“This is kind of a nationwide issue people are dealing with in determining the bulk-specific gravity for RAP and shingles,” Jackson points out. “The problem is that the fine particles in the RAP and shingles float when you submerge them in water; this makes it very difficult to determine the bulk-specific gravity directly using the traditional AASHTO T-84 and T-85 test methods.” The National Center for Asphalt Technology (NCAT) has a method where 1 percent virgin binder is added to the RAP to keep the fine particles from floating. However, the methods all have different shortcomings, Jackson says. It makes it difficult when you are trying to come up with a hard and fast number and there are different approaches that people are using.

The RAS, “eliminates the potential for rutting in the roads because of the stiffer asphalt binder and the fibers they add to the road, but there is still concern about cold weather cracking and fatigue cracking,” says Jackson.

In 2012 the Missouri Department of Transportation (MoDOT) revised its specs and raised the minimum VMA requirement in lower-volume mix designs so cracking issues do not occur, says Jackson. “I think the ultimate solution is that we go to straight mixture performance testing instead of looking at each component,” Jackson says. “There are several performance tests out there. People have their own opinions on what is the best method; I think that a combination of fatigue cracking and rutting potential tests will provide the best performance predictors in the future.”

Go to www.facebook.com/BetterRoadsMagazine for a RAS photo album. For coverage of Illinois’ use of RAS and Illinois Tollway Authority, EPA and Illinois DOT testing, go to www.betterroads.com, then click on “Web Exclusives.”

A tiny Arkansas town gets ready for a flash flood

Small towns can face the same big problems as big towns when it comes to stormwater infrastructure. This one faced an essential emergency culvert repair without a lot of reserve funding waiting at the bank.

They didn’t fund their way out it; they thought their way out of it. Three days before a flash flood.

When a large sinkhole developed down the side of the main thoroughfare in the town of Garner (pop.284), in central Arkansas, some quick decisions had to be made, especially when it was discovered that the drainage pipes installed more than 30 years ago were completely rotted.

“You could see down about 3 feet into that sinkhole,” Arnold Sewell, the mayor of Garner, Ark., tells Better Roads.

A patch was made over the two culverts where the hole was on this south main highway, Sewell says. “But once we got started, [we discovered] there was a bigger hole in the side [of the pipes] than anticipated. The road has four culverts about 50 yards apart. The second set of culverts, where the water main is, has a concrete bridge over them. “These were completely washed out inside,” Sewell says. In fact, the pipes were so eroded they backed up water, always sending typical drainage into the overflow culvert that was supposed to be reserved for emergency stormwater.

The “usual” solution may not be the best

Completely replacing the pipes was going to be very difficult for the small community. The town could dig and replace the pipes, but money wasn’t available. Plus, doing a complete replacement would mean closing down the road. There are a number of school buses that travel that road each day, and closure would mean rerouting them 10 to 12 miles out of the way, Sewell says.

A secondary road could be used, but 18 wheelers can’t use that road.

But with an already-sinking roadbed, something needed to be done, and done quickly. That’s when Sewell discovered an alternate solution – simply relining the pipes.

The culvert reline method cost-estimate was 40-percent less than the cost of digging and replacing the pipe – based on the initial quote. Overall, by relining the bad pipe instead of digging it up and replacing it, this saved money and did not have to shut down a main road. Sewell says it would have cost $68,000 to dig out the pipes. “That is for demolition of the culverts and replacing the galvanization,” Sewell says. “The head bowl, which was about 4 feet tall and about 20 feet, need to be replaced. Plus, if you add in the engineering feel, it would have been around $75,000.”

Replacing only the liner pipe cost the cash-strapped town about $46,000. When engineering fees are figured in, Sewell says, the city saved about $27,000. “We’ve been asking for donations,” he says. “You can fill out for a grant, but it could take a year. The road would be gone by then and it doesn’t do you any good.”

The relining of the culverts was completed this spring. Snap-Tite/ISCO Industries supplied the high-density polyethylene (HDPE) pipe liner, with Baldwin Construction serving as the contractor on the project.

Just three days after the project was completed, flash floods slammed into Garner and its surrounding community. There was tremendous rainfall, but in addition to local floodwater, came water from an upper community.

“It came down pretty quick and increased our water flow,” Sewell says. However, the relined pipes were able to handle the water, and Sewell says, it “made a big difference knowing that the road was safe. If the water would have stayed in the pipes or backed up and we had a lot of heavy traffic, who knows what would have happened,” says a relived mayor.

Sewell says the project highlighted the vital need to have funding available for infrastructure. Garner, he says, was able to fund this emergency work with donations and cashing in some bonds, but the current uncertainty without a reauthorization of SAFETEA-LU is making it difficult to keep up roads. “You have to have a road to drive,” Sewell says. “We really need to get this highway bill passed or we’re go have to go back to gravel roads.”

Take the Rains

Be an APWA-certified stormwater manager

The American Public Works Association (APWA) has developed the Certified Stormwater Manager (CSM) credential program to promote excellence and commitment to public service by advancing the knowledge and practice of stormwater management to benefit the community, public agencies and the profession.

The certification is intended for water experts in both the public and private sectors who coordinate and implement stormwater management programs for city, county, state, provincial, and federal agencies.

These are the men and women that assist in administering drainage, flood control, and water quality programs and may also be involved in budgetary oversight, long-term planning, policy development, and other administrative activities. Since its inception, the APWA CSM program has certified 67 stormwater managers in North America.

The certification serves as a “hallmark of excellence” for U.S. and Canadian water experts in public works. The program highlights the CSMs’ professional expertise and their dedication to advancing water quality programs and services in their community, which include state and federal requirements related to stormwater runoff including management of public education, illicit discharges, erosion control, post-development runoff BMPs, system maintenance, water quality monitoring, data analysis, and reporting, as well as drainage and flood control, notes APWA Executive Director Peter B. King.

The APWA Stormwater Manager Certification program is conducting computer-based testing and is now available at more than 170 sites in the United States and Canada. Computer-based testing cuts costs by lowering travel and accommodation costs for applicants and minimizes time away from work. It also gives candidates more chance to take the exam – rather than being locked into a specific date they can choose a date and time within a two-week testing block. And results are immediate rather than taking up to two months to hit your mailbox.

For details type “CSM” into the search box at www.apwa.net

The curriculum for the Certified Stormwater Manager (CSM) designation includes the following:

PROGRAM MANAGEMENT:

• Overall storm management

• Program administration

• Communication/Education

• Planning and design

WATER QUALITY and QUANTITY:

• Regulatory programs

• Structural best management practices

• Hydrology and hydraulics

OPERATIONS and MAINTENANCE