“Preserve” can be defined as to keep in good condition or to keep safe from harm; to prevent decay and maintain. Think about preserving or upkeeping your home’s exterior. Rather than tearing everything down and starting over, properly timed preservation techniques can help to keep your house looking like new and functioning properly and efficiently. Some of these techniques include painting or replacing the windows or the roof. Applying these treatments at the right time prevents costly repairs and even complete reconstruction.

Maintaining an asphalt pavement is like preserving your house. There are times you don’t have to do full reconstruction of the road or even mill off the surface of the pavement. There are treatments to extend the lifespan of the pavement, keeping it in good condition and safe for the driving public. Not only does this extend the life of the pavement, but it also benefits the bottom line. Roads are a capital investment. Maintaining them properly can save money and stretch a tight budget.

Simply stated, pavement preservation is applying the right treatment to the right place at the right time. An asphalt deterioration curve can help determine timing and treatment.

Surface preservation treatments are meant to delay the need for rehabilitation or milling of the structural asphalt. As the pavement moves from fair to poor condition, the treatments available to you must be more structural in nature. Figure 1 shows an asphalt deterioration curve with different treatments applied to the pavement as the condition deteriorates.

Pavement preservation treatments can be divided into four categories:

• Surface treatments
• Pre-treatments
• Recycling and reclamation
• Base treatments

Some common surface treatments are crack seal, rejuvenating fog seal, micro surfacing and thin lift HMA overlay. Let’s discuss those in some depth.

Crack Seal

Placement of material into existing cracks.

Crack filling is the placement of modified asphalt material into non-working cracks to prevent the infiltration of water and incompressible materials like gravel and sand. Routing and sawing is performed as needed to create a more uniform area for the filler allowing for better control and ensuring a proper seal to the existing pavement.

There are certain conditions that should exist for a pavement to be a good crack sealing candidate:

• New or recently rehabilitated surface
• Limited linear cracking
• Little or no secondary cracking
• Little or no raveling at crack face
• Good base support
• Limited structural deterioration

Cracks must be cleaned and dried prior to applying the filler or sealant. Having a dry road is even more important than the air or pavement temperature. It’s also important to keep the meter tank no less than ¾ full to maximize the effective melting point.

How to Crack Seal Right, Step By Step

Rejuvenating Fog Seal

Process of restoring chemical properties of the aged asphalt binder.

A rejuvenating fog seal or asphalt rejuvenation does not provide any structural improvement, rather it’s an emulsion that penetrates the top 3/8” of pavement restoring the aged asphalt binder. The effectiveness of the treatment is typically determined by the reduction of the binder viscosity. It is a “top of the curve” preventative maintenance and extends a typical pavement life by 3-5 years per treatment when applied at the right time.

Asphalt rejuvenation works by re-proportioning the aged fractions (asphaltenes) to the fluid portion (maltenes) of the asphalt binder. The maltene fraction gives the asphalt binder its flexibility. Asphaltenes effects the viscosity of the asphalt; as this fraction increases with age, the viscosity also increases making the pavement less pliable and prone to cracking. Thus, by restoring the maltene to asphaltene ratio like that of a new binder, the life of the pavement is extended. This process is not unlike a bowl of spaghetti (asphaltenes) with sauce (maltenes).

Over time the water in the sauce evaporates causing the sauce to dry out or age making it difficult to move or separate the spaghetti. Refreshing (rejuvenating) the sauce brings the bowl of pasta back to life, making it easier to separate the spaghetti noodles and move them around. Rejuvenation aims to restore the pavement’s flexibility and resistance to cracking.

MDOT, NCAT Show How to Place New Rejuvenating Fog Seal

Micro Surfacing

Surface treatment mixture of polymer-modified asphalt emulsion, mineral aggregate, water, and additives. The mixture is made and placed on a continuous basis by mixing the ingredients using specialized equipment.

The micro surfacing formulation is based on mix design parameters: resistance to raveling, lateral displacement and resistance to moisture damage. The emulsion plays a key part in micro surfacing. The wrong emulsion or an emulsion that doesn’t work well with the other components can cause issues such as long set times, durability, and delamination.

Remember that temperature, humidity, and wind conditions all affect emulsion break and cure times. If using a micro surface in combination with crack sealing, ensure crack sealing material is not excessive where it can be picked up by the paver tires and spreader box runners. Screen the material immediately prior to loading the mobile support unit so there is no possibility of contamination when re-handling the material. Treat vegetation with herbicide early to prevent it from returning after the project is completed.

Many agencies have reported ten years or more of service life when micro surfacing is installed on newer asphalt pavements in good condition. However, when used as a “band aid” or as a stop-gap measure on an asphalt pavement in marginal condition in order to delay rehabilitation/reconstruction, surface treatments including micro surfacing will have a shorter service life. Having the proper mix design for the micro surfacing is critical to ensure all materials work together. Some emulsion chemistries do not work with certain aggregate combinations, and some react poorly to excessive mineral filler.

How to Micro Surface

Thin Lift HMA Overlay

Applied thin layer (1.5 inches or less) of hot mix to the surface of the road.

Thin lift overlays can be used to extend the life of a pavement by sealing small cracks and providing a new riding surface. Overlays can be applied with or without milling, but the existing pavement must be in good condition since the overlay provides little additional structure. Thin lift overlays are available as conventional dense graded mix, open graded friction course (OGFC) and stone matrix asphalt (SMA).

Thin lift overlays improve ride quality and surface friction, correct surface defects, enhance appearance, seal the surface, and reduce splash and spray.

Regardless of the pavement preservation technique, quality control and quality assurance (QC/QA) are vital prior to, during, and after construction. Look at these three elements of the typical preservation project—the emulsion, the distributor truck, the aggregate.

Emulsion

• Certificate of Analysis (Manufacturer)
• QC Sampling and Testing
• Temperature

Distributor Truck

• Calibrate ➔ Quantity
• Proper Pressure, Spray and Coverage
• Speed

Aggregate

• Proper Certified Test Results
• Quality Control Results
• Mix Design

While the materials for HMA and pavement preservation treatments are the same (aggregates, liquid binder, emulsions), the equipment varies, and the material testing is different. In efforts to standardize the testing and material selection, the American Association of Highway and Transportation Officials (AASHTO) created an emulsion task force (ETF) in 2008. Material standards, design standards and construction guides have since been developed, and in a 2012 passage from the Moving Ahead for Progress in the 21^st Century (MAP-21), state DOTs could begin to use federal funds for pavement preservation.

This high level of confidence was only one benefit to the on-going AASHTO standardization efforts. Other benefits include educating the next generation of DOT staff and preservation crews and offering a consistent way to select materials, test and design. Constant collaboration and education will only further enhance the quality of the pavement preservation techniques, ultimately extending the life of our pavements.

Best Practices for Asphalt Overlays and Thin Lifts

The team at Asphalt Testing Solutions & Engineering LLC, Jacksonville, Florida, prepared this back-to-basics article for the AsphaltPro and PreservationPro audience.

Ensuring that chip sealing and fog sealing equipment is properly set up is key to a quality product. However, according to Scott Shuler of Shuler Consultants LLC, Fort Collins, Colorado, improper equipment setup is quite common.

Shuler is one of the authors behind the Transportation Research Board (TRB) “Guide Specifications for the Construction of Chip Seals, Microsurfacing and Fog Seals” (NCHRP 14-37), alongside R. Gary Hicks of R. Gary Hicks LLC, Chico, California.

During a recent TRB webinar, the pair shared some best practices for setting up your equipment—and your crew—for chip seal and fog seal success.

The Best Practices of Crack Sealing

Equipment Requirements

A chip sealing operation requires a broom, an asphalt distributor, an aggregate spreader and compaction equipment.

The asphalt distributor should be calibrated, accurately control application rate, provide uniform coverage in both transverse and longitudinal directions, and hold a specific temperature. It should also have an adjustable spray bar and correct nozzles to allow for double to triple overlap, Hicks said.

The aggregate spreader should be calibrated, adjust to varying widths, distribute the aggregate uniformly in transverse and longitudinal directions, and deliver the desired application rate using computerized controls.

The job will also require several rollers, Shuler said. “I don’t know how many projects I’ve seen where they only have two or even one roller trying to keep up with that distributor truck and spreader,” he said.

Shuler also said it’s important to wait until 85 percent of the moisture within the chip or fog seal has evaporated before sweeping to ensure the emulsion has enough adhesive power to keep the chips in place. Hicks adds that the broom should be motorized, with plastic bristles and vertical control pressure.

1. Take the emulsion’s temperature.

Emulsion should be around 180 degrees Fahrenheit or above. “If the emulsion is too cold, it will not spray well,” Shuler said.

2. Check your nozzle size.

It’s important to use the right nozzle for the job. “Various distributor manufacturers indicate what sort of nozzle should be used for various shot rates,” Shuler said. These guidelines may be in the equipment manual, or in some cases, may be mounted directly on the distributor truck itself. It’s also important to ensure nozzles aren’t clogged to prevent uneven application.

3. Ensure proper nozzle placement.

It’s also important that your nozzles are placed correctly, at an angle between 15 and 30 degrees. The truck often comes with a wrench designed to turn that nozzle to the correct angle. “Very often, the operator of that distributor truck may not know that and uses a crescent wrench or something else and does this by eye,” Shuler said. “That’s possible if you’ve got an experienced operator, but it’s much better to use the wrench that comes with the truck.”

How to Manage Chip Sealing

4. Adjust the height of the spray bar.

If the distributor truck’s spray bar is set too high, you’ll get streaks as a result of overlap. If the bar is set too low, there may be streaks of uncoated pavement between the nozzles. Shuler reminds us that if we’re seeing streaks of any kind, it’s important to stop and make the proper adjustments. The binder should double- or triple-overlap, Hicks added.

5. Check your spray rate.

Some operators may be surprised to learn that they shouldn’t be relying on the gauge on the back of their distributor truck to know how much material they’re spraying. “All that gauge is for is to tell you if you’re empty or not,” Shuler said. “Don’t think you’re measuring gallons with this.”

The only way to tell if a truck has sprayed the correct rate is to dipstick the tank, Shuler said. That’s why every truck comes with a dipstick. “I don’t know how many times the operator didn’t even know there was a dipstick up there,” he added. The operator should dipstick before starting to spray, spray a set area for which the distance and width is known, then dipstick again to determine spray rate.

Because the tank gauge is a ball float style of gauge with a large pointer and an engraved dial, the numbers are often close together which makes it tough to read, said Brian Horner, field sales manager at E.D. Etnyre, Oregon, Illinois.

“The other issue is the pointer itself can be grabbed by anyone and possibly moved,” he said, “so the measuring stick is more accurate and reliable.” Etnyre is currently working on new digital tank gauges that will display the gallons in the tank on the computer screens at the rear and cab.

Upgrade Micro Surface and Slurry Sealing Operations

6. Calibrate the spreader.

“A really simple way to tell if the aggregate is spread uniformly is to look at the veil,” Shuler said.  If you want to measure the amount of chips, which Shuler recommends, measure the distance and width to get rid of two or three truckloads to get your chip spread rate.

7. Use the right number and type of rollers.

“Those chips need to see that roller more than once in order to embed,” Shuler said. He recommends a speed below 3 miles per hour with a rubber-tire roller with equal tires and equal tire pressure.

“Steel does not conform to the chip shape like rubber and tends to crush the chip,” Shuler said. “This changes the shape, size and texture of the chip, all of which are undesirable. Some chips can withstand this abuse, but many cannot.”

Hicks recommends that the first pass be within two minutes of applying the aggregate and that there be at least three complete passes.

Pickleball is a rapidly growing sport. With the ability to retrofit pickleball lines on existing sport courts, it’s a simple service to up-sell recreation sites. Here’s how to surface and stripe a pickleball court.

There are more than 2.5 million pickleball players in the United States, according to the Sports & Fitness Industry Association. In fact, pickleball is one of the fastest growing sports in the country. According to the USA Pickleball Association (USAPA), the sport has seen a 650 percent increase in participants in the past six years, mostly among younger players.

The sport has been described as a combination of ping pong, racquetball and tennis, and requires players to use special paddles to hit a wiffle ball over a net in the center of the court. However, pickleball courts are much smaller than a tennis court (though, larger than a ping pong table!).

How to Pave a Tennis Court

The ability to retrofit pickleball lines on existing sport courts makes this a simple service when making that sale to residential managers upgrading recreational sites.

Here, AsphaltPro explains the best practices of how to surface and stripe a pickleball court with help from Jeff Gearheart, director of SportMaster Sport Surfaces, Sandusky, Ohio.

Plan Your Court

If you are constructing a pickleball court from start to finish, one of the first considerations will be the size and layout of the court.
Pickleball courts measure 44 feet long and 20 feet wide, including the court’s boundary lines. The USAPA Rule Book recommends a minimum total playing surface of 30 by 60 feet, though 34 by 64 feet is preferred. Anytime multiple courts will be in close proximity, fencing between the courts is important to protect players on other courts.

Just as with other sport courts, it is ideal to orient the court north-south to limit the sun obstructing players’ vision and the impact of shadows on the court surface.

Due to the relatively small size of pickleball courts, it’s possible to create more than one pickleball court within a tennis court or a basketball court.

This article does not set out to explain how to pave a pickleball court. For that, it’s ideal to follow the best practices of paving tennis courts or other sport courts, taking special care to ensure proper drainage.

For a more detailed overview of the pickleball construction process, check out “Pickleball Courts: A Construction & Maintenance Manual” from the American Sports Builders Association and the USAPA. The 108-page manual offers design, construction and maintenance instructions and is available at the USAPA store.

Prep & Clean

Gearheart first recommends checking the overall condition of the surface for any cracks, low spots or other deficiencies. Cracks should be sealed and low spots should be leveled before you proceed.

“Courts are normally built with a 1 percent slope for drainage, but water will collect in any bird baths,” Gearheart said. “Not only will the standing water break down the acrylic and pavement, but players will also have to wait longer before than can play after rain.”

One leveling option is SportMaster’s acrylic patch binder, which is an acrylic liquid mixed with Portland cement and sand. It can be poured in low spots and then scraped even with a screed or straight edge. Once it sets up, it can be sanded down as needed.

The pavement should also be clean and dry. If not, the coatings may not adhere properly. Gearheart recommends brooming, blowing or power washing the surface to ensure it is free of dirt and debris. “The best option is to power wash the surface, but if it is visibly clean, brooming or blowing should be enough,” he added. He also recommends trimming any grass that may be sticking over edge of the pavement.

It is also recommended to apply the coatings with ambient temperatures between 60 and 90 degrees Fahrenheit for best results.

A pickleball court is roughly 880 square feet.

Resurface & Cushion

The process of surfacing a pickleball court varies, and may include application of a resurfacing material and/or a cushioned material, in addition to paint for color and texture and line-striping the court boundaries. Some jobs, such as repurposing tennis courts for pickleball, may only require line-striping.

Once all pavement distresses have been repaired and the surface has been cleaned, Gearheart first recommends applying an acrylic resurfacer. “It won’t fill cracks, but it will fill any voids in the pavement and it will hide any repairs you’ve made,” he said. “And, most importantly, it sets a nice sandpapery texture that cushion and color can more easily adhere to.”

How to Pave a Sport Court: Practice Really Does Make Perfect

The acrylic resurfacer is particularly important for courts that intend to add a cushion layer. “Without the resurfacing acrylic, the rubber wants to pile up instead of grabbing onto the texture below,” Gearheart said, “and the rubber in the cushion product will fill the voids so the surface won’t feel as cushioned.”

A cushioned pickleball court is created by applying multiple layers of an acrylic with small rubber granules with a soft rubber squeegee. To ensure even application, Gearheart recommends pouring out the cushion product in relatively small amounts, to prevent piles of rubber at the end of the squeegee pull. After spreading the cushion acrylic, he also recommends being gentle while scraping any high spots.

Most public courts are hard courts, while private and tournament facilities tend to opt for cushioned courts. Gearhart said cushioned pickleball courts tend to be more common than other types of courts, due to their smaller size and the sport’s historical popularity with an older demographic.

Color the Court

Next comes the color coatings. USAPA recommends 100 percent acrylic paint for outdoor courts.

The color is typically applied with a minimum of two coats. “Pickleball courts are smaller and are often used for doubles,” Gearheart said, “so there’s more wear because the players are always scuffing the same little boxes. It may be worth adding an extra coat to extend the life of the surface.”

The type and amount of silica sand per gallon will be specified by the manufacturer. SportMaster’s acrylic resurfacer uses roughly 14 pounds of 50-60 mesh silica sand per gallon of concentrated resurfacer. Color coatings use a rounded and finer sand, roughly 70-90 mesh.

“Tennis facilities prefer a more angular sand because it’ll grab the ball and slow down play,” Gearheart said. “With pickleball, I’ve seen rounder sand so it doesn’t chew the balls up as much.”

Although tennis courts tend to be painted blue or green, the USAPA says pickleball courts can be painted any color as long as it contrasts with the lines of the court. “It seemed in the past that they may have been choosing different colors so they wouldn’t be eclipsed by tennis,” Gearheart said, “but now pickleball is a big sport in its own right.”

In hotter climates, Gearheart said lighter colors that are more solar reflective are more popular. “Light gray courts can be 40 degrees cooler than a black or dark green court.” Light courts can also help brighten up indoor courts.

“You also want to choose a color that contrasts from the color of the pickleballs,” Gearheart said. Pickleballs are most often yellow, orange or lime green. “Generally, colors opposite from each other improve contrast. For example, if the balls are yellow, paint the court blue.”

Striping a Pickleball Court

Pickleball courts measure 44 feet long and 20 feet wide and are divided into five main areas. See the diagram alongside this article for a visual representation of the dimensions.

Note that the total area of the court includes the boundary lines, so ensure the outer edge of the painted line conforms to the final court dimensions. All boundary lines should be two inches wide.

The USAPA recommends white lines for dedicated pickleball courts, but the most important thing is that the boundary lines are a contrasting color to the court’s surface color. If adding lines to multi-purpose courts, the association recommends lines in the same color family as the court itself. Take care to tape over multi-purpose courts’ existing lines, so they remain the predominant line, and leave a 3-inch gap where any lines intersect.

Straight application of the lines is important, not only for a professional-looking court but also to ensure fair play of the game. The most common application method for pickleball lines is to use a line taping machine and then apply paint with a brush or roller.

“Companies will occasionally use a line striping machine, but overspraying the tape is a common issue,” Gearheart said. Additionally, the traffic paints that can be used in striping machines are often thinner, which means they are more likely to bleed and offer less surface texture and less pigment, resulting in a shorter wear life.

When painting the lines with a brush or roller, Gearheart recommends using a textured white line paint so the lines are a similar texture to the playing surface.

Due to the surface texture, there will be small voids under the tape that paint may bleed into. For perfect lines, Gearheart recommends using a clear-drying anti-bleed primer after taping but before painting the lines. Once the primer is dry, paint the lines.

Allow the paint to dry 24 hours before use. Play on!

In part one of our two-part series on the best practices of micro surfacing and slurry seal applications, we share all of the basics and best preparation practices. Part two, forthcoming in the Fall 2020 issue of Preservation Pro, will dig into the best practices on the job site.

Upgrade Micro Surface and Slurry Sealing Operations, Part 2

Experimentation with slurry sealing may have begun in the U.S. in the 1930s, but it wasn’t until the 1960s–with the advent of truck-mounted slurry seal pavers and the development and integration of quicker-setting cationic emulsions–that the treatment began to grow in popularity.

The surface treatment is designed to protect the pavement from oxidation and raveling, provide skid resistance, and stop moisture intrusion into the asphalt pavement, while minimizing disruptions to the traveling public with its quick construction times.

Its sister surface treatment, micro surfacing, didn’t reach the U.S. market until the 1980s, but has also grown in popularity since its introduction–both for its leveling capabilities and quick set capabilities.

“In the last one or two years, we’ve had customers who used to bid every micro surfacing project they could find having to pick and choose because there’s so much of this work out there now,” said Jimmy Kendrick, Director of Sales at Bergkamp, Inc., Salina, Kan. “The more educated people become on these applications, the more popular we’ve seen them become. They just need to see the benefits of it.”

What is Slurry Sealing?
What is Micro Surfacing?

Both slurry seal and micro surfacing are specifically-designed mixtures of asphalt emulsion, aggregate, water, mineral filler and additives, mixed in set proportions, and uniformly spread across a prepared surface.

Slurry seal is about one stone thick, just under ¼ of an inch or smaller, while micro surfacing is usually applied at multiple-stone thickness. Although slurry sealing can contain polymer-modified asphalt emulsion, micro surfacing always contains polymer-modified asphalt emulsion.

When to Micro Surface or Slurry Seal

Slurry seal and micro surfacing is ideal for pavements suffering from flushing, polished aggregate, raveling, oxidation and light to moderate cracking, said Dr. Andrew Braham of the University of Arkansas. Micro surfacing can also fill minor rutting and prevent cracks from growing wider, due to its use of polymer-modified emulsion. However, neither treatment will prevent cracks from returning, Braham said.

Despite their benefits, these treatments have no effect on the structural capacity of the existing pavement. As such, they should only be used to extend a roadway’s service life, not in the hopes of repairing structural damage.

Benefits of Micro Surfacing and Slurry Sealing

Both slurry sealing and micro surfacing are cost-effective treatments that will seal the pavement surface, fill small top-down cracking and restore surface friction.

They are suitable on a variety of asphalt pavement types experiencing various levels of traffic, from highways and collector streets to residential streets and culs-de-sac, according to the Pavement Preservation and Recycling Alliance (PPRA). Both treatments maintain drainage patterns and curb reveal.

Additionally, slurry sealed surfaces can be returned to traffic usually between one and four hours after application, and micro surfaced pavements, typically within one hour.

“Another benefit of micro surfacing is that it can be used alongside other applications,” Kendrick said. For example, it can be used alongside a cape seal, where a chip seal is covered with a slurry seal or micro surface.

Slurry sealing can extend a pavement’s service life between five and seven years, when applied correctly, and micro surfacing can extend service life between six and eight years.

Materials for Micro Surfacing and Slurry Sealing

There are five primary materials in micro surfacing and slurry seals: emulsion, aggregate, mineral filler, additives and water.

According to Pat Denney, Micro Surfacing Manager for Road Science, Tulsa, Oklahoma, slurry seal emulsions can be produced with a cationic quick-set emulsifier (CQS), a cationic slow-set emulsifier (CSS), or an anionic slow-set emulsifier (SS). CSS and SS emulsifiers depend largely on evaporation for curing, making them much slower to cure.

“By contrast, a micro surfacing CQS emulsifier will have a chemical break that begins to kick water out of the system,” Denney said. “Basically the system is stabilized during mixing, and then destabilized chemically to trigger a quicker curing process.”

Aggregates used for these treatments should be highly angular with minimal dust or clay, high resistance to abrasion and high soundness.

• Type I (#200 x 1/8 in. [3 mm]) offers maximum crack penetration and seals minor raveling and is used in low traffic areas.
• Type II (#200 x 1/4 in. [6 mm] stabilizes moderate to severe raveling, provides a smoother surface and quieter ride than Type III, and is used in moderate traffic conditions.
• Type III (#200 x 3/8 in. [9.5 mm]) corrects severe raveling, offers high skid resistance and structure for leveling, and is used in heavily trafficked areas.

These are the aggregate types, as outlined by the International Slurry Surfacing Association (ISSA). However, many state specs use their own aggregate types, which may differ from ISSA’s.

Check out AsphaltPro’s article “New AASHTO Pavement Preservation Standards, Explained” at www.theasphaltpro.com.

The mineral filler, additives and water are the same for slurry sealing and micro surfacing.

Mineral filler, such as portland cement, hydrated lime or limestone dust, can adjust breaking properties and improve mixture consistency. Additives, such as emulsifier and aluminum sulfate, can accelerate or decelerate the break time

Water should be free of contaminants or harmful salts.

“Water can have some effect on mixture characteristics,” Denney said. “The use of pond water in a micro surfacing application is not recommended due to increased risk of the presence of deleterious materials or other types of contamination that could negatively affect mixing and cure rates.”

Mix Designs for Micro Surfacing and Slurry Sealing

To ensure proper performance of a project, a mix design must be conducted to determine the compatibility of the aggregate, emulsified asphalt, water, mineral filler, and other additives.

Mix designs should be used to determine the compatibility and ratio of the above materials. They should be performed according to ISSA A105/ASTM D3910 for slurry sealing and ISSA A143/ASTM D6372 for micro surfacing.

For project success, the lab performing the mix design should have experience in mix designs for these treatments and should be aware of your project’s parameters. Since temperature, humidity and wind can affect cure time, these variables should also be considered.

Micro Surfacing and Slurry Sealing Equipment

These treatments can be applied either with a truck-mounted paver or a continuous paver. Truck-mounted pavers are typically used on projects with shorter pulls, while continuous pavers are used on longer pulls, such as highway jobs and can minimize construction joints.

Typically, jobs with truck-mounted pavers use two or more on the job, since they must load material at the stockpile. Mobile support units, or nurse trucks, deliver materials to the continuous pavers, which can load materials while continuing to apply the material.

Truck-mounted pavers require a smaller crew and can drive to the jobsite, while continuous pavers minimize construction joints. That’s why it’s important to have enough trucks on hand to maintain a steady supply.

Both types are equipped with a spreader box, which may or may not have augers to move material and may or may not have a drag on the back to texture the material.

The job may also require a distributor truck if tack is required, or a rubber tire roller if required.

Calibration and Test Strips

“You can have the best crew and the best site preparation in the world, but if the calibration isn’t right, you will have problems,” said Tim Harrawood of Vance Brothers, Inc., during a Transportation Research Board webinar. Calibration ensures compliance with the approved mix design, and the factors determined through the calibration process aid in application rate verification and overall material usage.

“It’s extremely important that application equipment is calibrated in the presence of an agency representative,” Harrawood said. “This could help eliminate potential issues caused by proportioning of the materials.”

Generally, Harrawood said, calibration will take place only once per project, though some agencies allow the transfer of calibrations. It can be performed on truck scales or platform scales, but all scales should be certified. He said a seasoned crew can perform the calibration in less than two hours. Each manufacturer has their own preferred calibration method, so consult the manufacturer’s manual.

Harrawood also recommends placing a test strip for evaluation and agency approval.

“Test strips assure adequate workmanship, aesthetics, and cure time of the mixture is achievable when applied with the personnel, equipment, and materials intended for use during execution of the project,” Harrawood said. He said the test strips should be performed in similar conditions as those expected during actual application. For example, test strips for a daytime project should be performed during the day.

Stockpile Success

For micro surfacing and slurry sealing jobs, the contractor will set up a staging area for the stockpiles of materials, equipment storage and maintenance.

“Your stockpile location is key,” said Zach Jensen, Product Support Manager at Bergkamp. “When the stockpile is so far away, it’s going to take longer for trucks to get back to the job site.”

The stockpile site should also be arranged for safe and optimal traffic flow.

The delivery site for the aggregate should be flat and free of vegetation. Denney recommends a gravel, cement, or asphalt surface.

“A lot of these jobs will be in remote areas where a concrete pad for your aggregate isn’t available,” Jensen said. “Use the first few loads to make a flat base for the rest of your aggregates to avoid digging into the underlying material.”

Regardless of the underlying material, loader operators should take care to avoid contaminating the aggregate with dirt, vegetation or other contaminants.

Verify that the onsite stockpiles of aggregate have not become segregated by wind or rain or contaminated with deleterious materials. Denney suggested conducting occasional checks for stockpile moisture content, as well.

Ensure the screening deck is free of contaminants and is in good working order. When screening the aggregate, Harrawood recommends screening it directly into the nurse truck. Any oversized stones could create drag marks in the mat behind the paver. “This is absolutely the best method to limit exposure to oversize aggregate,” he said. Some states with strict dust abatement rules, particularly western states, may not allow screening. “If that’s the case, work closely with the trucking firm to ensure the aggregate isn’t contaminated with oversize particles.”

It’s also important that the delivery transports, transfer tanks, and tanks on the project that will be used for the emulsion are also free of contamination, and that the screens on equipment are cleaned daily.

Additives may include both wet and dry additives. The storage area for these additives should be clean and dry, and additives should be covered by a tarp to protect them from moisture. It’s also important to ensure that the tanks, drum barrels or totes are contaminant-free.

There should be enough materials at the stockpile site and enough mobile support units to transport it to the job site to constantly supply the micro surface machine with material. This both maximizes production and minimizes transverse joints.

Stay tuned for the Spring 2020 issue of Preservation Pro to learn about the best practices of micro surface and slurry seal applications on the job site.

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Sources

• FP2 Preservation Toolbox
• Federal Highway Administration (FHWA) and FP2’s slurry sealing and micro surfacing pocket guides
• Pavement Preservation and Recycling Alliance’s RoadResource.org Treatment Center
• Transportation Research Board’s micro surfacing and slurry sealing webinar
• AsphaltPro’s “How to Micro Surface” article
• Jimmy Kendrick and Zach Jensen of Bergkamp, Inc.

Micro surfacing is a polymer-modified, cold-application paving process. It relies on specialized equipment to combine polymer-modified asphalt emulsion, mineral aggregate, water and additives, and uniformly spread this mixture over a properly prepared surface.

The asphalt emulsion breaks onto the pavement surface. Then, when the mixture cures by loss of water, it will be bonded to the existing pavement to create a long-lasting wearing surface.

You may be more familiar with the process’s parent product, slurry seal. However, the use of polymer-modified asphalt emulsion in micro surfacing (versus standard asphalt emulsion in slurry seal) allows for the surface to set in less than an hour.

According to Pat Denney, Micro Surfacing Manager for Road Science, Tulsa, Oklahoma, slurry seal emulsions can be produced with a cationic quick-set emulsifier (CQS), a cationic slow-set emulsifier (CSS), or an anionic slow-set emulsifier (SS). CSS and SS emulsifiers depend largely on evaporation for curing, making them much slower to cure.

“By contrast, a micro surfacing CQS emulsifier will have a chemical break that begins to kick water out of the system,” Denney said. “Basically the system is stabilized during mixing, and then destabilized chemically to trigger a quicker curing process.”

Although it may take up to four hours or longer for a slurry seal to cure enough to open for traffic, micro surfacing is designed to allow straight rolling traffic within one hour of paving.

In addition to a faster curing time, the added durability that a polymer-modified emulsion offers makes micro surfacing an attractive option for busier roads.

“Micro surfacing has a broader range of applications including interstates and state highways where slurry seal cannot and should not be used,” Denney said. Slurry seal emulsions can be made with or without polymer, but micro surfacing emulsions always have a minimum of 3 percent polymer by weight of asphalt according to specification.

It’s important to note that, despite its benefits, micro surfacing has no effect on the structural capacity of the existing pavement. As such, micro surfacing should only be used to extend a roadway’s service life, not in the hopes of repairing structural damage.

“The road that’s ideal for micro surfacing doesn’t need to be in perfect condition,” said Jimmy Kendrick, Director of Sales at Bergkamp Inc., Salina, Kansas, “but it should be in fairly good condition.”

Minor distress can include some cracking, oxidation, raveling and rutting.

Before placing the micro surface, Kendrick said it’s important to repair any damage on the roadway. Cracks must be sealed and all patches should be made.

One pavement distress that may not need to be repaired prior to micro surfacing is rutting up to 1 ½ inches deep.

Applying a micro surface can also improve skid resistance and surface permeability. Other benefits of micro surfacing include no loss of curb reveal, no transitions at intersections and driveways, and no alteration of drainage.

Whether micro surfacing is done as a single or double lift, adjustments to manholes, inlets and the like are not necessary.

“Another benefit of micro surfacing is that it can be used alongside other applications,” Kendrick said. For example, it can be used alongside a cape seal, where a chip seal is covered with a slurry seal or micro surface.

A micro surfacing treatment can last up to 7 years. Over the next few pages, we’ll outline the best practices of micro surfacing so your treatment looks good and lasts long.

Micro Surfacing Weather

Although the required ambient temperatures change from state to state, Kendrick said most states require temperatures of 50 degrees and rising and no chance of freezing temperatures within 48 hours of application.

Even at the correct ambient conditions, the humidity, cloud cover or even shade on the roadway can affect the curing of the micro surface.

“Emulsion formulation is very important and will change over time as the season changes from spring to summer and then to fall,” Denney said.

Meet Micro Surface Specs

Denney said that most, if not all, agency design specifications for micro surfacing are based on ISSA A143 Recommended Performance Guidelines for Micro Surfacing.

Although the inspection requirements for micro surfacing vary from agency to agency, Denney said all agencies require quality control on the aggregate being delivered to the stockpile site.

“This may be accomplished, for example, by sampling and testing aggregate for gradation and sand equivalency on every 200 tons of aggregate delivered,” Denney said. “If each sample passes the tests and is within the stockpile tolerances of the design, then the aggregate can be used and placed in the larger stockpile of passing material.”

The contractor must also provide emulsion test results from their producer showing that the emulsion passes specification, Denney added. “Some or most agencies require that the emulsion producer provide a sample of emulsion to the agency for testing,” he said.

The agency must also ensure that what is supposed to be laid in pounds per square yard by weight of mix or by weight of dry aggregate is what they are actually getting. This can be accomplished by requiring contractors to provide load weight tickets for aggregate delivered to the roadway.

Micro Surface Materials Handling

Micro surfacing mixture is made and applied on the job site with a specialized machine. The machine combines the materials, which include mineral aggregate, polymer-modified asphalt emulsion, water and additives, based on the project’s specifications.

These materials should be stored as near to the job site as possible.

At the stockpile staging area, it’s important that the delivery site for the aggregate is flat and free of vegetation. Denney recommends a gravel, cement, or asphalt surface.

Regardless of the underlying material, loader operators should take care to avoid contaminating the aggregate with dirt, vegetation or any other contaminant. It’s also important to ensure the screening deck is free of contaminants and is in good working order.

It’s also important that the delivery transports, transfer tanks, and tanks on the project that will be used for the emulsion are also free of contamination, and that the screens on equipment are cleaned daily.

Micro surface also requires a reliable source of potable water.

“Water can have some effect on mixture characteristics,” Denney said. “The use of pond water in a micro surfacing application is not recommended due to increased risk of the presence of deleterious materials or other types of contamination that could negatively affect mixing and cure rates.”

Additives may include both wet and dry additives. The storage area for these additives should be clean and dry additives should be covered by a tarp to protect them from moisture. It’s also important to ensure that the tanks, drum barrels or totes are contaminant-free.

The additives may include control additives–typically a wet additive–that is used to control mix time without sacrificing cure rate, Denney said. “The control additive allows the paving crew to determine the mix and cure rates of the mixture.”

This is typically a solution with a small percentage of emulsifier used in the production of the emulsion. “However, in the Western United States,” Denney added, “aluminum sulfate is used extensively because of the high reactivity of the aggregates in that region.”

Additives may also include portland cement or hydrated lime to stabilize the mixture during the mixing phase.

It’s important to ensure there are enough materials at the stockpile site and enough mobile support units to transport it to the job site to constantly supply the micro surface machine with material. This both maximizes production and minimizes transverse joints.

“Having enough mobile support units will affect your production rate and are part of the continuous paving process,” Kendrick said. Typical jobs covering 6 to 8 miles per day require between four and six mobile support units, he added.

Denney added that it’s also important to conduct occasional checks for stockpile moisture content.

“Every component of the mixture is based on dry aggregate weight,” Denney said. Checking aggregate moisture is integral to ensure delivery of the appropriate amount of mineral filler, water, control additive and emulsion for the mix used on the job. “Any major variation in moisture will significantly impact proper mix quantities of individual ingredients.”

The stockpile area may also serve as the best location to place test strips to ensure appropriate mix and cure rates.

How to Micro Surface

As with any pavement preservation method, the surface of the job should be clean and dry.

You will also need to grind up any thermoplastic striping within the area to be micro surfaced and cover all castings, such as manholes and inlets. You should also place a damp-proof membrane at the beginning and end of the application area to ensure the straight lines.

When the surface is ready, it’s time to tack.

As mentioned earlier, micro surfacing mixture is made and applied on the job site with a specialized machine.

The materials are mixed in a very specific process, in measurements based on the mix specification, within the pugmill. The composite material is then fed into a spreader box to spread it over the full width of the traffic lane in a single pass, often ⅜ of an inch thick.

Micro surfacing can be laid at a thickness of two to three times the size of the largest stone in the mix.

A double lift may be required for a more robust wearing surface, on roads with higher traffic counts, or where rut filling or leveling is employed. It’s recommended to wait a minimum of one day between placing the first lift and the second lift, but the exact waiting period required will depend on the agency and the traveling speed on that roadway.

“Micro surfacing is looked at in pounds [of aggregate] per square yard [of material],” Kendrick said. “So if you’re trying to achieve a higher level of pounds per square yard, you’ll need to do multiple lifts.” He said two lifts may also be required on roads that have a bit more cracking.

If there are deeper ruts to be filled, the crew may make one pass with a rut box attached to their micro surfacing machine. The box is designed in such a way that it augers material right into the rut so it’s not spread out over the width of the lane, Kendrick said. “And then it has a rear strike off to make it level.” Then, the crew applies micro surface to the entire pavement on the second pass.

Whether applied in one lift or two, it’s important that the meet lines are made at the center of the road, the center of a lane, or the edge of a lane, but never in the wheel path. The meet line should overlap no more than 3 inches, maximum.

The micro surfacing machine should also travel in a straight path to maintain the longitudinal joint and to ensure edge lines along shoulders, intersections, driveways and curbs are straight. Denney also recommends maintaining a consistent speed of operation to avoid outrunning support vehicles.

As the micro surfacing machine travels along, the crew may need to perform some hand work around driveways and intersections, as well as smooth out any rough spots of larger aggregate that may make it through the screener to the pavement.

“[Handwork] is where the most talented of the crew is needed,” Denney said. “A good squeegee person can make a good job look great and an inexperienced squeegee person can make a good job look poor.”

The new surface may initially appear dark brown, but will be black after it cures.

It’s also important to keep traffic off of the newly micro surfaced pavement until it cures. Turning traffic may need to be kept off the surface even longer.

Maintain Micro Surfacing Machinery

Properly maintaining equipment is also key to ensuring a high quality mat.

Both Denney and Kendrick recommend cleaning the spreader box every time the machine is stopped.

The primary and secondary strike-offs should also be cleaned of “any dried, broken material to ensure a consistent cosmetic appearance of the mat”, Denney said, adding that it may be necessary to stop specifically to clean the box and strike-offs if they are leaving drag marks in the mat.

Denney also recommends allotting enough time at the end of the day for maintenance and clean up, and that the foreman or superintendent inspect the equipment before wrapping up for the day.

Troubleshoot Common Micro Surfacing Issues

Denney said the most common mistakes when it comes to micro surfacing include lack of attention to detail, lack of understanding the differences between micro surfacing and slurry seal, and a lack of proper training.

He added that the International Slurry Surfacing Association, or ISSA, offers a four-day training workshop every January and that the Pavement Preservation and Recycling Alliance (PPRA) is also a helpful resource for information and online training.

“However,” Denney added, “the biggest mistake anyone can make is thinking that we know it all. Staying humble and always asking ‘why’ is crucial.”

“It’s easy to think micro surfacing is like hot-mix paving, but that’s simply not the case,” Kendrick said. “There are a lot of factors affecting the material and the chemistry, and the crew needs to be fully aware of that.”

He recommends establishing a good relationship with an emulsion supplier early on to help guide contractors new to micro surfacing through the process.

Efficiency. Dedication. Precision.

These are traits every top-notch athlete must have. They’re also the traits every paving crew laying sport courts must have. After all, no tennis player wants to play uphill, no basketball player wants to dribble through a puddle and no runner wants to trip on a seam in your mat.

Like succeeding at any sport, sport court paving perfection comes with practice. That’s exactly what makes Superior Surfacing Systems, Bloomingburg, New York, an expert: years and years of practice.

Although Superior performs all kinds of paving–and all kinds of construction, for that matter–sport courts are somewhat of a specialty for the company. Superior President Keith Reardon estimates that the company’s project manager, Kevin Murphy, has paved around countless sport courts in his 35 years in the industry.

Located near the popular mid-20th-century resort area of the Catskills, Superior is also in somewhat of a unique situation.

“So many of those hotels, resorts and camps had tennis courts and basketball courts,” Reardon said. Kevin was involved in many of them.

“We have the expertise within our personnel, it’s a part of our history and it’s a profitable market because it isn’t easy and not everyone can do it,” Reardon said. “Most paving contractors advertise that they do tennis courts, but that’s usually not the case–at least with any great success. Experience paving sport courts is critical.”

You’re Only As Good As Your Last Game

Most recently, the Superior crew paved some basketball courts at Sullivan County Community College. The courts were part of a much larger project–nearly all of which was performed by Superior crews–including removing old courts, prepping the site, performing fencing and more.

The $380,000 project began in July of this year and wrapped up in September. The main paving portion of the project involved replacing Sullivan’s tennis facilities with two full-size regulation collegiate basketball courts.

“These old courts were built in the early ’70s and had structural problems from the start,” said Sullivan Athletic Director Chris DePew. “Over time they were used less and less until the mid-’80s when they were completely abandoned.”

In total, the area included two tennis courts, one handball court and a basketball court, near Lazarus Levine Residence Hall, which was built in 2003.

“Since the residence hall was so close, we wanted to find a way to fix them up and make it a usable facility for our students,” DePew said. In 2015, the SUNY Sullivan Athletic Department received a $1 million private donation so they set to work.

Despite housing existing courts and requiring slightly less site work than a brand new installation might require, the courts were overgrown, neglected and located in a swampy, wet area of campus.

“That really held us up because we had to go grade and reshape the area so water would stop accumulating and it would dry up so we could get to work,” Reardon said.

After grading, draining and drying the area, Superior’s crews placed some large graded aggregate to help stabilize the soft ground. Then they put in 12 inches of crushed stone subbase, followed by 2 inches of dense binder, 1.5 inches of type 7 top mix with 1/4-inch aggregate and four-coat acrylic color system installed by Copeland Coatings, Inc. of Nassau, New York.

Playing By The Rules

Although it may sound similar to many other paving applications, sport courts present a unique set of challenges.

Of course, one of the most significant special challenges is following the parameters set in place by sports associations.

According to Reardon, the caliber of competition plays a big role in the precision required.

“For example, if you were paving courts for the U.S. Open, where it’s an extremely competitive event and world class venue, it gets critical,” Reardon said. But, for most projects like community centers, residences and school courts, the rulebook is pretty standard, he adds.

“Once you establish what they are, you know those parameters,” Reardon said. You know the criteria, the size, and all other requirements. “And then it’s repetition.”

A very valuable resource for contractors looking to get into paving sport courts is the American Sports Builders Association. Coincidentally, Superior’s painting subscontractor’s project manager, Mike Edgerton, is the president of ASBA’s tennis division.

The association has four divisions (tennis, track, field, and courts and recreation), each of which has its own construction manuals available online at sportsbuilders.org/publications. Tennis guidelines would be available under the tennis division, but basketball–while similar in many ways–is housed under courts and recreation.

ASBA began in 1965 as the U.S. Tennis and Track Builders Association, but then expanded to include artificial turf fields, courts and recreational facilities. In 2004, it changed its name to ASBA. The Maryland-based association has more than 400 member companies across the country.

ASBA also certifies builders for various applications. For example, Edgarton–an ASBA member for around 25 years–is a certified tennis court builder.

“You have to pass a test and prove you have enough experience in the field over a certain number of years,” he said. You also have to keep up with the industry and re-certify every three years.

“I’d trust someone who paves tennis courts to pave a parking lot, but not vice versa,” Edgerton said. “A lot more goes into the design of the court than you’d think.”

For example, the court should have a 1 percent grade, “no more or a little less,” Edgerton said. “One inch every 10 feet is a good standard.”

But, he adds, it must be pitched in the same plane. For example, you wouldn’t want a court to slope down from the net on both sides.

“That’s just fine if all you care about is it shedding water, but the players will technically be playing uphill the whole time,” he said. “They’ll be serving uphill and the ball will be landing on a downhill slope.”

Pave a Sport Court with Precision

“When it comes to paving courts, there’s special care and precise equipment that goes into it,” Reardon said.

It requires checking once, twice and even three times. It should be checked with a laser and paved with equipment that can hold a precise grade. His own crew uses a Carlson CP-90 paver with automation and Hamm compaction equipment.

Reardon said having equipment equipped with electronics is integral. “You should have a joint matcher and grade controls on your machine, as well as a laser to shoot and check grades,” he said.

The binder course, in particular, is checked and double checked with a laser to give the crew a chance to level any imperfections before placing the surface course.

“You have to be on the high-end side of quality control,” Reardon said. “You have to turn out a really tight, dense, pretty project. Not many people do it very well.”

Beyond getting the grade and slope just right, Reardon said there is also a really high standard regarding segregation.

“You don’t want much stone in the top mix,” he adds.

Superior is often using the same mix on its sport courts as it does on most other projects.

Courts usually require 2 inches of binder, followed by 1.5 inches of 1/4-inch final mix and four coats of acrylic resurfacer and color.

A Sporting Good Challenge

Another unique challenge for many sport courts is access.

“When they’re initially built, they’re tucked into hillsides or on someone’s estate and there isn’t much thought about how crews will get back there to rebuild or repave that court,” Reardon said. “It’s not like a parking lot or a road that’s meant to be driven to/on.”

So, a lot of times, his crew has to build its own access point to the project. “We need to take out landscaping, put a temporary road through someone’s lawn or a park to get our equipment onto the court again, and then restore what we’ve disturbed once we’re done.”

For example, on a recent tennis court project at a private residence, Superior’s crew had to use lighter trucks than usual. So, when Reardon’s team is paving a new court, he tries to keep access in mind.

Another consideration for new courts? The sun.

“You don’t want to put courts east to west because it would be unplayable at sunrise and sunset,” Reardon said. You also don’t want much tree cover because the leaves on the court could collect mildew and create problems.

“We help customers pick out the best spot for the court,” Reardon said. “Sometimes the lay of the land dictates something that isn’t ideal, but we’ll always give our advice.”

Coat it in Team Colors

“One of the potential problems on finished sport courts is, when the painting crew comes, if the court doesn’t drain properly and there are bird baths, they have to do leveling with leveling compounds and that’s going to make it more expensive,” Reardon said.

That’s–yet another–reason to leave behind a high-quality mat.

In Reardon’s case, it’s also a matter of being a good neighbor. His painting subcontractor, Copeland Coatings, rents the office space next to Superior’s office.

“We used to color our own courts, but we decided it was too time consuming,” Reardon said. “There were too many trips back and forth, coating and curing, coating and curing. I’d rather use those personnel to be out paving somewhere.”

“When it comes to painting, my advice would be to subcontract it to a pro, because that’s the finished product, the icing on the cake,” he added. “That’s what everyone is going to see when they look at the court. You can construct a wonderful court underneath, but if the paint is streaky or there are other cosmetic issues, people will think you’ve done a bad job.”

Copeland Coatings manufactures and distributes acrylic paint throughout the northeast, but they also color running tracks, tennis courts, basketball courts and more. They’ve been making and using their own acrylic since the ’70s. “We coat everything, but we don’t build anything,” Edgerton–Copeland project manager and ASBA Tennis Division president–said.

After painting around 300 courts per year throughout the northeast, Edgerton knows a thing or two about proper acrylic application. His top recommendation?

“Have enough crew on hand for the job, because the paint dries really quickly,” he said. For example, if they’re painting one court, the crew may be only two guys, but two courts would require three.

“You have to make sure the stream of material stays at a consistent viscosity while you’re squeegeeing fast enough,” Edgerton said. “You also have to have enough material for the job so you don’t have to stop, which would leave marks.”

It’s also important to remember that the ambient temperature will affect the viscosity of the paint and the finished look of the job. “You also wouldn’t want to paint on days it might rain,” he adds.

Both Edgerton and Reardon have seen a trend towards more unique paint choices over the past few years.

“Years ago, it was either green or red, but now we see purple, gold, blue,” Reardon said. “There’s a lot more personalization with color palettes and logos.”

Edgerton estimates that around 70 percent of the tennis courts he paints these days are U.S. Open colors–blue and green–while basketball court colors run the gamut.

“We do a lot of logos these days that we paint with stencils,” Edgerton said. “It’s a nice little extra to make the court more unique or different.”

After the Game is Won

If the old maxim that you’re only as good as your last game is true, Superior Surfacing Systems just might deserve a trophy.

“Superior did an amazing job keeping the impact on campus to a minimum during construction,” DePew said. “The project will have a profound impact on the quality of life of our residential students living less than 50 yards away from the facility.”

Down the road, Superior will be converting the area near the new basketball court into a sand volleyball court, as well as paving new tennis courts for Sullivan.

Let’s just say sport courts will continue to be a winning part of Superior’s business strategy.