As Good as New

Nov. 12, 2013

More genuinely than for any other aspect of most communities, the decisions about resurfacing roads depend on the money available. One thought that seems almost universal is that the authority responsible for repairs should not consider raising taxes to achieve the desired results. Local authorities, especially those for smaller communities, feel they have to juggle their financial decisions to satisfy the demands of their constituents, and that means that some popular, existing services will weaken, that some people who expected improvements won’t get them, and those of us with pet projects to be done will blame government in general for being unconcerned. I was just reading a speech by an influential legislator, in which he explained that local governments blame their states, states blame the federal government, and everybody can blame the president, as he’s the end of the line. So it becomes a matter of (mostly party political) blame…and the surfaces of the roads and streets will have to wait another year. That’s not how it’s supposed to be. At some time, people who demand high standards of safety and convenience for their vehicles and themselves are going to have to pay for them. That may mean higher taxes.”

What are we going to do about those deteriorating roads, streets, and highways? Where do we place our priorities? The first challenge is to find ways of resurfacing today that could avoid the problems made by yesterday’s solutions. Although we live in a society where it seems we have to have somebody to blame for everything, I don’t think we should look back on the road designers and builders of yesteryear and say they were lacking in foresight. They used technologies and materials that were available at the time. Popular asphalt roads were resurfaced with asphalt, but what would you expect? As the problems for every county magnify, it’s not only the cost of the actual resurfacing that must be considered but also the long-term cost of this or that solution. Do we spend X dollars on a solution that will last five years, or 2X dollars on the solution that will last 20 years? It’s becoming sheer math, simple arithmetic. That is something that most people should understand, if the situation is explained to them honestly and clearly.

One solution would be to vary the quality of the resurfacing according to the usage of the road. That may upset some people, but temporarily only, say the authorities. First impressions and comments from users of the resurfaced Lyona Road in Crawford County, PA, were not good, but the Pennsylvania Department of Transportation advised users to be patient with the surface. To recycle this road, PennDOT used a recycled asphalt pavement process. This means that the milled surfaces of larger roads like highways and interstates are mixed with cold oil and applied to some of the state’s secondary roads. Lyona Road serves some 1,500 vehicles per day and has a 10-ton weight limit. The savings are worth noting. Last year, for example, recycled asphalt pavement cost PennDOT just over $28 per ton. Hot mix, a superior alternative, cost more than two-and-a-half times as much! Using the cold oil solution saved the state just over $3 million last year in one region alone, a savings that enabled more miles of road to be resurfaced. The disadvantage of the cold oil process (duly and promptly noted by some users) is that the first results seem rough, but the surface does settle gradually, according to the amount of traffic, usually in a month or a little more. Crews will come back at that time to seal the resurfaced road. It’s a solution that is not perfect, but it works well enough for the people and traffic it serves and it saves money.

A Worsening Problem
Deteriorated roads will not go away. They are not made awful or better by political arguments or the social status or even the loudness of complaints of the people who use them. Time is a road’s biggest enemy, and has anybody ever managed to stop that? The weather plays a big role. Rain, snow, ice, sun, heat: All those temperature fluctuations that roads endure over the months contribute to the surface decline. If your community uses chemicals to treat snow and ice, that doesn’t prolong good surfaces. And then there’s traffic, the reason the road was built! If you have ever traveled anywhere, here or abroad, where the roads are always rough, you will understand readily how good many of our so-called awful roads are in comparison. There is no way to stop the natural deterioration of the surfaces of roads. The challenge is finding solutions for slowing down the effects of that natural deterioration.

Credit: Gomaco
Accurately placed and shaped concrete slabs are making strong gains in popularity for resurfacing roads.

One busy county in California has determined that paved roads should be resurfaced properly every 15 to 20 years to maintain a good, countywide quality. The lack of funds there means that many roads will be resurfaced every 40 to 60 years. Now and then some funds come along from the state or federal government to alleviate the situation slightly, but overall the county anticipates worsening conditions for its roads (about 500 miles of them). One solution starts with governments at all levels being made aware of the terrible condition of our nation’s infrastructure (including roads, bridges, and water supplies). Any quick-fix solution to these road-resurfacing problems is not going help our communities tomorrow; the problems will have worsened, the cost soared.

Many communities are coming up with less expensive and more feasible solutions. Some have decided to work together on a common problem, and it would not be surprising to see a group of neighboring communities investing in equipment that could be used by all in a planned rotation. Ingenuity (and not just financial juggling) may well solve some of these resurfacing problems nationwide.

District 8 of Caltrans in California is the largest, geographically, of the 12 statewide Caltrans districts, with four interstates and 32 state routes adding up to 7,000 lane miles within its boundaries. Historically, the technique for treating the deteriorating pavements has been to crack-seal, and to fill potholes using cold-mix asphalt. Those are labor-intensive treatments. Now sections of the roads requiring attention have increased beyond all anticipation while the money available has decreased as much in the opposite direction. Often pothole repairs last less than a year, with increased traffic demanding more and more. In recent years, the District 8 Area Maintenance, with John Hubbs as superintendent, has changed its approach, addressing the challenges by developing a rapid crack-fill solution that would seal not only the severe and most visible pavement cracks but also the entire roadway surface. That prevents moisture from compromising the road base. I saw some excellent information on this process from Western Emulsions of Dana Point, CA, and Main Street Materials of San Juan Capistrano.

Among the products used to perfect the innovative treatment of deteriorated roads Caltrans used PASS-engineered emulsions that have rejuvenating qualities to restore as well as seal the pavement. PASS emulsion was developed in 1980s and first patented in 1992. It was the first engineered emulsion to combine successfully a liquid polymer-modified asphalt with a rejuvenating agent. That combination gives a material that is tough but highly ductile, forgiving when used with a variety of aggregates and effective at penetrating and restoring the existing asphalt. For some years the crack-fill solution with the PASS treatment worked very well, using black volcanic cinders as a helpmate. Then the price of volcanic cinders soared (like the original volcanoes?) and something more affordable was required. Hubbs and his team determined that recycled asphalt pavement (RAP) might work. What a concept! It’s estimated that this process will save Caltrans enough money to do 10 times the number of lane miles that could be afforded previously with the district’s materials budget.

At a recent project, some 300,000 tons of RAP millings were generated. Rather than pay for the material to be hauled away and

Credit: Vogele
However thick or thin your overlay will be, all sizes of
efficient pavers are available to give good results.

recycled as a low-cost base material, District 8 discovered that the RAP could be converted on site to a high-value product that met California’s chip specification. “We were sitting on approximately $7,500,000 worth of asphalt liquid at today’s rack prices,” comments John Hubbs. “The relatively high residual asphalt content in turn allowed us to reduce the amount of emulsion needed for our mix design, another savings that made our dollars go further.” The PASS process has proved to be successful for this agency, so the team there developed an appropriate game plan, to use the RAP chips generated from the existing stockpile. With good cooperation from Main Street Materials, Western Emulsions, and Pavement Recycling Systems, Caltrans used the stockpile to produce two products: a five-sixteenths-to-three-eighths-inch RAP aggregate chip that meets state specifications, and a RAP slurry product that uses the smaller fine materials made through the crushing and screening operation. Caltrans retained several thousand tons of RAP chips for future projects, in addition to the large quantity of leftover fine material planned for use in a RAP slurry system.

Savings in dollars were not the only benefits Caltrans recorded over one particular stretch of pavement-35 miles, in fact:

  • Less emulsion was required because the aggregate was precoated with quality asphalt binder.
  • During the production phase, the RAP was highly workable and remained so for several weeks.
  • The stones worked well with a cool emulsion system containing an asphalt rejuvenator.
  • The project team noticed there was remarkable adhesion of the stone to the PASS CR emulsion after the roadway sweeping.
  • The existing asphalt covering the rock resulted in unusually good delineation, a feature much preferred by agencies.
  • The project produced a stockpile of RAP stones and fines ready for use in future projects.

Proven Remedies
Conversation about roads and pavements seem to have centered too often on the basic differences, along with advantages and disadvantages, of asphalt and concrete. One of the most successful ways to resurface worn pavements has been the method known as whitetopping. That combines concrete and asphalt in a friendly alliance. It has been used successfully for surfaces that do not have high-speed traffic: surfaces such as city intersections and alleys, airport pavements, residential roads, and parking lots. Curing time can be less than 24 hours.

Whitetopping can reach strength of 3,000 psi and last two or three times as long as asphalt resurfacing. In the long run, concrete overlays can serve for 20 to 40 years. It’s not only the lower initial cost that is appealing to users but the fact that the longer life reduces the need for maintenance. The use of the existing asphalt as the base for the remedial whitetopping also means that material is used that could have been wasted by using other methods.

As with every road construction or reconstruction project, the preparation is most important. Some contractors, to save time, mill off the amount of existing asphalt that will be replaced by whitetopping. If there are serious flaws in the underlying asphalt they must be repaired before pouring to ensure a good finish to the job. If you have potholes or ruts that are deeper than 2 inches, they should be repaired first. For the placement of the whitetopping, many contractors will recommend the use of laser screeds to get precise placement of aspects like crowns and pitches and to be able vary the thickness from, say, 2 inches to 3 inches to 6 inches all in one pass. Good, well-planned joint spacing can make a huge difference. The most successful projects seem to have short joint spacing so that you achieve a kind of paving system of small blocks.

Just north of Indianapolis, on US 36 near Fortville, the job required an ideal substrate for the placement of a thin hot mix asphalt overlay. The milling machine used was a Wirtgen W 250 with a 12-foot, 6-inch fine-texture drum. This is Wirtgen’s most powerful cold mill, and it made quick work of the project (5.5 miles long, 40 feet wide), shoulder to shoulder. “We are using a fine-tooth drum to scarify the road a quarter-inch over the full lanes,” explains Dave Money, superintendent, Mid-America Milling Co. (MAMCO), of Jeffersonville, IN. “At the end, we are milling a one-and-a-half-inch butt joint, 150 feet out. We are also milling out 8-foot shoulders.” MAMCO already owned a Wirtgen W 2200-12 cold mill with fine-texture drum, but the W 250 was speeding production and saving fuel. “The fuel economy is a lot better, even with two motors running,” says Money. “In a 12-hour period, the older W2200-12 would go through about 400 gallons of fuel, while the new W 250 goes through 270 gallons in a 12-hour period, and it’s a more powerful machine!”

“For super smooth, bonus-winning, thin lift HMA surfacings, cold milling of the existing, worn surface with a fine-tooth drum is a must,” asserts Jeff Wiley, senior vice president at Wirtgen America Inc. “With a conventional drum, and relative to ground speed, your peaks and valleys patterns will be relatively high and deep. If you are not placing a lift that’s thicker than one or one-and-a-quarter inches, the rough surface can reflect through to the paved surface. With a five-sixteenths-inch bit spacing (or less), the definition of a fine-toothed drum, an owner or contractor can minimize the potential reflection of the peaks and valleys through the thin lift surface.” Dave Money of MAMCO adds that the state wanted the road surface “scratched up” a bit before putting the HMS lift on it. “With the heavy truck traffic on this road, they did not want the asphalt lift to move around, shoving the asphalt one way or the other.” The fine texture drum on this project had 536 cutting tools, as opposed to 315 cutting tools on a standard 12-foot, 6-inch drum. The paving contractor placed one-and-three-quarter inch of HMA and it was being compacted to one-and-a-half inch.”

The advances made in the design and performance of milling machines have contributed enormously to the efficiency of resurfacing. It’s not so long since contractors groaned when they heard instructions for milling, whether it was a bridge deck or a part of a street. Today’s milling machines have changed that attitude. Today’s milling machines can buy time for some communities. Some agencies, especially our huge rural areas, have used fine milling to shape up their roads and remove rutting and areas where (in intersections, for example) asphalt has been shoved by traffic. A fine milling drum in a cold machine can repair the driving surface sufficiently, giving the authority more time to find the funding necessary for full-scale pavement repair.

Fine milling (like the drums described in Wirtgen’s comments above) has been especially useful when done before thin overlays. You have a binder course and a surface course with almost all asphalt projects, with the binder taking the load and the surface course sealing the top and providing the needed friction. The binder mix will have larger aggregate, while the surface mix is thinner, with smaller aggregate, some of it less than a half-inch in size. When you mill for such an overlay, you don’t want a drum with a spacing that will yield peaks and valleys; that would not allow a smooth asphalt surface. Do the milling with a finer texture drum, and those peaks and valleys could be half the size, with no negative effect on the top layer at the surface. For these efficiency reasons, and to earn bonuses, contractors will choose to work with equipment from a single manufacturer (such as the Wirtgen Group with its reclaiming/recycling equipment, asphalt compactors from Hamm Compaction, pavers from Vogele America).

Another Approach to “Mill and Fill”
In paving, we can never overestimate the value of preparation. I asked Kyle Hammon, technical marketing coordinator at Roadtec (an Astec Industries company), about milling as a foundation for good resurfacing. “Conventional mill-and-fill projects require a one to two inch removal of an existing road surface followed by an overlay of hot mix asphalt,” explains Hammon. “When performed correctly, these projects can yield positive results with exceptional durability and smoothness. This process can be improved by performing the milling with a double-hit cutter drum and overlaying the surface with an ultra-thin bonded wearing course.” The objective of the milling operation is to produce a pavement surface that is true to line, grade, and cross-section, while maintaining a uniform surface texture. The milling portion is critical, because any flaws will compromise the finished surface of the project. As the existing pavement is removed, close attention must be paid to surface pattern, cut depth, grade/slope controls, tooth wear, and ground speed of the machine.

“Smooth paving can’t occur without smooth milling,” affirms Hammon. “When milling at depths of 1-2 inches, the double hit Roadrunner cutter drums from Roadtec have produced excellent surface patterns at high ground speeds. The Roadrunner drums are laced in a way that increases the longitudinal smoothness of the milled surface with fewer teeth than traditional micro drums. Surfaces milled at 1-inch depths with Roadrunner cutter drums have passed the ASTM 965-96 Sand Test at a speed of 100 feet per minute. The ASTM 965-96 is a common quality specification for smoothness of a milled surface.”

For the paving portion of the project, a more innovative option would be to pave a 1-inch bonded wearing course with a Roadtec SP-200e spray paver. The SP-200e is equipped with a spray bar placed directly in front of the screed, so that a uniform tack coat can be applied to the milled surface just before it’s paved. This method prevents trucks or other equipment traffic from removing the tack after it’s applied. A uniform tack coat will increase the bond strength between the milled surface and the new layer of pavement. Higher bond strength will increase the road’s resistance to reflective cracking, rutting, and other common types of surface failure. The SP-200e also utilizes a gravity-fed hopper that receives the mix from a Shuttle Buggy material transfer vehicle. The Shuttle Buggy’s remixing capability helps to control physical and thermal segregation within the asphalt mix. The shuttle buggy’s 25-ton surge capacity also allows the paving process to move continuously in the event of trucking issues.

“Paving thin overlays by means of a spray paver is an economical method of pavement resurfacing,” says Hammon. “Milling the existing surface the correct way can remove problematic areas and enhance the quality of the new surface. The combination of these methods can provide smoother, more durable roads with a lower life cycle cost than other alternatives.” Different manufacturers of equipment and products are going to tell you their solutions are the best. They should do that; that’s how we advance in any area of construction. But how are we going to decide?

It’s not a Question of Right or Wrong!
One technique for resurfacing may be ideal here, but no so perfect there. From all the research I’ve read and heard, I would offer the opinion that one of your most practical approaches to finding the best method of resurfacing is to ask other communities what they have found. As one facet of resurfacing’s appeal is the length of time it lasts, it does make the opinion of somebody who has had a resurfaced pavement in good shape for several years more important than the publicized good looks of another site. Whether the solution is asphalt, concrete, a combination of both, or some other ingenious method devised to satisfy the needs of, say, quieter, rural roads, longevity is a prime concern. As the money available for resurfacing seems to shrink, so the requirement that the resurfacing last a long time becomes more important. Ask your neighboring communities and read about communities nationwide that have done resurfacing to decide which approach could be best for your particular needs.

Listen to experts at the state level, too. With so many roads nationwide being the responsibility of the states where they are located, it’s clear that states can save money and headaches if they address the problems of local communities. A good example of state involvement comes from Ohio. There you can come across Smoothseal. It’s the industry name for Ohio Department of Transportation (ODOT) Specification Item 424. It’s a fine-grade, polymer-modified, asphalt concrete, type A or B, and any hot-mix producer can produce Smoothseal to the ODOT specification. The materials are well suited for thin, preventive maintenance overlays; they are a blend of good quality aggregates with polymer-modified asphalt, and they give one of the most durable, densely graded paving mixtures available. Smoothseal is on its own among paving materials in Ohio because the state spec requires sand that has at least 50% silicon dioxide, SiO2 (quartz), to insure superior skid resistance. The association named Flexible Pavements of Ohio can give you further advice about Smoothseal, its production and its use.

Something else that can be most useful is a demonstration of new (and old) techniques for resurfacing. The National Pavement Preservation Conference was in Nashville last August there was an excellent demonstration of thin asphalt overlays on 10th Avenue North in the city of Nashville. The street was structurally sound but not so good in terms of the quality of ride for users. The unevenness was caused primarily by utility patches in addition to the usual patches in many city streets. Traffic on the street is quite light but three-point turns by trucks serving a large warehouse cause problems, too. To repeat, however, the structure is basically good. For this demonstration contractor LoJac Enterprises milled the pavement surface (with the material removed sent to the asphalt plant for future projects). After the milling, the area was swept. Then the tack coat was placed. This is a most critical step in thin asphalt overlays because the place where the old and new pavements join is so close to the shearing forces of traffic braking and turning.

Many states recommend, rule, and regulate the mixtures that can be used for paving, and the rules should be followed. The mix used in the Nashville demonstration, like other preservation treatments, served to seal off the surface so that it became a tight surface that helped eliminate water intrusion but was nonetheless a structurally sound mix. The mix is fine and can be placed thinly (about three-quarters of an inch); this makes it economical, too. The actual paving process for a thin overlay is the same as for more conventional paving, but we should remember than thinner layers cool more quickly than thicker ones. In doing a thin overlay, the contractors should remember to have the rollers working immediately behind the pavers so that they can produce excellent compaction.

There is much to consider with resurfacing, but it seems that time spent researching the best materials and methods will save impressive amounts of time and money in the longer run. Ask those who have been successful how they did it. Ask the good manufacturers what they recommend. The experts at companies like Caterpillar, Bomag, Roadtec, Terex, the Wirtgen Group, Gomaco, Bagela, and Western Emulsions have significant knowledge and experience.