Back in the mid-’70s, my personal profile was a cursed brew of idealism, pragmatism and acts of sheer self-indulgence.

kirk.landers@att.net

My burden was especially heavy in matters of environment and ecology. I could see the need for clean air, for example, but the awful cars that were produced in the middle of that decade in the name of cleaner air were a purgatory for driving enthusiasts.

I went along with the clean-air legislation, but I also rejoiced in the antics of the first couple of Cannonball Baker Sea-to-Shining Sea Memorial Trophy Dashes (also known as Cannonball Runs), the outlaw races organized by Brock Yates, one of the greatest automotive writers of the era. His rebellion against the 55-mph national speed limit, bad cars and the legislation that produced them, coupled with the sheer freedom of the race — its only rules were where it started and ended — were a great release from the burdens of saving the environment and the other trappings of good citizenship.

Highways presented a similar schizophrenic dilemma for me. As one who loved open spaces and fast roads, interstates and freeways were a blessing and a curse — the curse being the sprawl that resulted when fast roads made 20-mile commutes easy… at least for awhile.

By the end of the decade, mainstream environmentalists almost universally condemned freeways as the work of the devil. My protests that roads don’t make sprawl, lack of zoning does, fell on deaf ears. Once again, I found my tree-hugging instincts at war with a love for great roads, each quality an anathema to different political constituencies — and different groups of friends and associates.

It was like being a Vietnam veteran. Hawks liked that you were a vet but figured you for a drug addict. Doves were OK with the drug abuse but thought you were a killer. If you didn’t use drugs or kill innocents, people didn’t believe anything else you said.

So the fact that I loved roads and cared about the environment had to be my little secret in the ‘70s and ‘80s, like Aunt Bee’s brandy bracer or the reverend’s penchant for cursing when the other team scored.

Imagine then the freedom I feel in the 21st century when I can proclaim to my tree-hugging friends that our pavements are among the greenest man-made structures in our civilization. Asphalt is the most recycled product in the country, and concrete is very high on the list, too. Thanks to improvements in design, materials and processes, the service life of pavements has been dramatically extended, even as usage has skyrocketed. Carbon emissions in the processes that create concrete and asphalt have declined steeply in the past two decades, and continue that downward trend.

Porous asphalt, pervious concrete and open-graded friction course improve environmental water quality, enhancing sensitive ecosystems.

And here’s the other part: I can proclaim to my pro-industry friends that all of the advances in the environmental integrity of pavements have enhanced the cost effectiveness of pavements, too. Recycling reduces costs. Warm-mix asphalt extends the paving season and makes possible longer delivery routes while also enhancing compaction. Technologically-advanced concrete and asphalt mixes lead to thinner pavements and less material required to carry the same loads. The list goes on…

These are indeed great times for long-suffering closet-cases like me. Not only can I openly love roads and the environment, I can even confess to being a Vietnam veteran without losing friends.

Agencies looking for dollar value balanced with road quality are looking at concrete overlays

By Daniel C. Brown

This 8-inch unbonded, plain-jointed concrete overlay was placed on I-44 in 1999 in Webster County, Mo.

More than ever before, state departments of transportation (DOTs) and other roadbuilding agencies are choosing concrete overlays as a way to rehabilitate and preserve their existing pavements. Concrete overlays allow agencies to save the cost of removing an existing pavement. And significantly, concrete is generally more competitive these days with asphalt on a first-cost basis, as well as a lifecycle basis.

“Concrete overlays allow us to take the substantial equity that we have in our existing pavement system, which generations before us have invested in, and to hold onto that investment,” says Dale Harrington, P.E., principal senior engineer, Snyder & Associates, on behalf of the National Concrete Pavement Technology Center. “We can hold that investment by utilizing the strength of that existing pavement, be it in concrete or asphalt, and enhance it with a concrete overlay. That way, we bring the pavement into a whole new cycle without having to destroy the existing slab.

This bonded concrete overlay was placed 4 inches thick on asphalt and sawed into 4-foot-square panels. It’s on U.S. 60 in Neosho, Mo.

“The other major benefit of concrete overlays is sustainability,” says Harrington. “By leaving the existing pavement in place, and not wasting it, we are making the pavement even more sustainable. That is a huge plus!”

What’s more, concrete overlay technology has matured, which helps spur growth, says Leif Wathne, P.E., vice president of highways and federal affairs, American Concrete Pavement Association (ACPA). “In large parts of the country, there has been phenomenal growth over the past five years in concrete overlays,” says Wathne.

“Concrete overlays give states and other agencies an opportunity to seize a long-term solution,” says Gerald F. Voigt, P.E., ACPA president and CEO. “Most of the DOTs are operating under tight budgets these days, and we don’t have a new highway bill. A concrete overlay does not require an expenditure to tear out the existing pavement. Overlays are quite adaptable to a tighter budget scenario.”

Concrete overlays come in two primary categories: bonded and unbonded. The key difference is that with bonded overlays, the new structure depends on the underlying pavement – asphalt or concrete – to act in unison with the overlay. The new pavement is designed to count heavily on the strength of the underlying structure. Bonded overlays require that the existing pavement be in fair to good structural condition, and they are generally thinner than unbonded overlays.

Unbonded overlays treat the old pavement as a stable base for the new overlay. Unbonded concrete overlays, which are generally thicker than bonded overlays, are often placed to rehabilitate asphalt or concrete pavements that are in poor condition. Unbonded overlays do not require a bond between the new overlay and the existing pavement.

Both bonded and unbonded concrete overlays can be placed on three types of pavements: concrete, asphalt, or composite structures. Composite pavements are generally those where asphalt has been placed over concrete.

“The adoption of concrete overlays by DOTs has enabled them to introduce competition in a market segment where they traditionally have not seen much competition between the two industries,” says Wathne. “That competition enhances the ability of agencies to stretch their highway dollars.”

From 2004 to 2009, concrete overlays of 6 inches or less have grown from about 1.2 million square yards to about 5.4 million square yards, ACPA data shows. And according to bid-letting information, a total of 17 million square yards of overlays were built in 2009 and 2010 – and about half of that was composed of thinner overlays. “Most of it was built on existing asphalt pavement,” says Voigt. “So that is just a huge jump from what we have seen in the past.”

Wathne says that when you introduce the concrete pavement industry into the rehabilitation market segment, that not only lowers prices, it stimulates innovation. “You have another industry in there challenging the existing industry, and that is a good thing for the customer, which in this case is the DOT or the public sector, actually,” says Wathne.

In terms of innovation, ACPA’s Voigt points to a concrete overlay project happening this year on U.S. Highway 18 in Chickasaw and Fayette Counties in Iowa. There, contractor Manatt’s, of Brooklyn, Iowa, is building an unbonded overlay on 19 miles of two-lane roadway. This is the first such concrete overlay to be built one lane at a time, under traffic. Stringless concrete paving, by which automated machine controls guide the paver, opens up the project and allows concrete trucks access from the centerline side. A 24-hour pilot car will lead a group of vehicles first in one direction, then in the other.

The existing roadway is a 7-inch-thick concrete pavement topped by a 6-inch asphalt overlay. The asphalt overlay will be milled down by 1 to 1.5 inches, and a 4.5-inch concrete overlay will be applied, says Todd Hanson, P.E., a PCC engineer in the Materials Division of the Iowa DOT.

As evidence of the growth of concrete overlays, Voigt points to Kansas, where the DOT has recently let approximately 1.5 million square yards of concrete overlays for Interstate 70. “Those overlays are what we call a ‘6-by-6-by-6’ overlay – 6 inches thick and 6-foot-by-6-foot panels,” says Voigt.

“There is an upcoming national open house on that,” Voigt says. “It is essentially a mill-and-fill using concrete instead of asphalt. They are milling down and placing concrete to re-establish the grade that was there.”

In Missouri, MoDOT has built some 25 concrete overlay projects over the past 12 years, says John Donahue, P.E, construction and materials liaison engineer. Most of those projects have been built on Interstate highways, but some have been paved on lower-volume roads as well. Donahue says Missouri has placed several unbonded concrete overlays that use a geotextile as the bond breaker between the old concrete and the new.

“And we have done, to a lesser extent, a number of thin bonded concrete overlays,” says Donahue. “Typically those are about 4 inches thick. In that case, we actually try to get a bond with the asphalt below. We have typically used those at intersection locations where we have had historical rutting occurring on the asphalt.”

A third type of overlay in Missouri is what the state calls its “big block design.” It is an unbonded overlay – thinner than the state’s conventional concrete overlay, which is 8 inches thick. “We would construct it at 5 or 6 inches thick, and place it down on an asphalt surface, or even a concrete surface if we use the geotextile interlayer,” says Donahue. “Then we saw the pavement into 6-foot-by-6-foot panels.”

Technology transfer

ACPA and the National Concrete Pavement Technology Center (CP Tech Center) provide instructional information and provide training related to concrete overlays. ACPA’s education and training program, for example, focuses on delivering training on various aspects of design, construction and pavement rehabilitation using concrete overlays.

The CP Tech Center offers workshops to state agencies on concrete overlays through the National Concrete Consortium. The consortium is a group of 21 states that have pooled their resources and joined together to work on concrete pavement issues and solutions, Harrington says. This NC2 group meets annually to hear speakers and discuss concrete pavement issues.

The CP Tech Center, in partnership with the Federal Highway Administration (FHWA), also provides technical support to DOTs that are considering such overlays. “We have been providing technical experts to assist the DOTs with identifying suitable candidate pavements for the overlays, helping them with the specifications and assisting with construction support,” says Tom Cackler, P.E., director of the CP Tech Center.

Harrington, who works full time for the CP Tech Center and is its former director, says concrete overlay expert teams have visited 22 different sites across the nation over the past two-and-a-half years. An example comes from South Dakota, where the DOT requested an expert team’s services.

The project was constructed on South Dakota Route 50 in 2009. “It was an existing 8-inch concrete pavement with 10-inch shoulders,” says Harrington. “The South Dakota DOT placed an asphalt interlayer as a bond breaker, then a 7-inch unbonded concrete overlay.

“The Center’s team, including FHWA, completed a presentation on overlays to the South Dakota DOT and gave them a site evaluation field review of Highway 50. The team provided comments on design and specifications as they were being developed. Finally, the team provided guidance during the construction and sent the Center’s mobile laboratory to the project for a week. The lab completed testing of material properties for South Dakota DOT. The Center’s team assistance was provided at no cost. When the project was complete, we sent them a final report and evaluation.”

Harrington says when the expert team program concludes in mid-2012, the CP Tech Center will publish a report on all the sites that have been visited. FHWA has requested that the full report include lessons learned about concrete overlays during the expert team consultations. That full report will be shared with all state transportation departments, Harrington says. States visited to date include Delaware, Georgia, Illinois, Louisiana, New Mexico and Virginia. Others involved include Maryland, Minnesota, Nevada, North and South Dakota, Pennsylvania, Texas, Washington state and West Virginia.

“So far, four states have done the actual construction,” says Harrington. “Some of them, such as Virginia, are working on them right now. Virginia built one this year; the others will build projects as they get the funds to do so.”

In North Dakota, the state has completed two concrete-on-asphalt overlays, says Clayton Schumaker, an assistant materials engineer with the DOT. The most recent one was finished this summer – a 5-mile project on ND Highway 200 near Hillsboro. A portion of the existing pavement consisted of asphalt with an aggregate base, and the remainder was a composite pavement with a concrete base paved in 1948.

The roadway consists of several segments, so various overlay thicknesses were used – ranging from 5 to 7.5 inches – to account for the different existing pavements and varying traffic loadings. Two major industrial facilities bring heavy truck traffic on ND 200 in the project area – and both facilities requested concrete, based on its performance since 1948, Schumaker says.

“One consideration was cost, and our engineer’s estimate says the concrete overlay is less expensive than doing full-depth asphalt reclamation then placing an asphalt overlay,” Schumaker says. “We’re looking at concrete overlays for a number of other projects where we have high-traffic volumes and the rehabilitation strategies are limited to full-depth reclamation, total reconstruction or the concrete overlay.”

Technical summary

In addition to technical support from the expert teams, the CP Tech Center has published “A Technical Summary of the Design of Concrete Overlays Using Existing Methodologies,” dated May 2011. The document provides an overview of the concrete overlay design process and identifies some of the more sensitive variables inherent with three different software procedures: (1) the 1993 AASHTO Guide for Design of Pavement Structures; (2) the Mechanistic-Empirical Pavement Design Guide (MEPDG); and (3) the ACPA method for bonded concrete overlays on asphalt pavements (BCOA).

The first method, the 1993 AASHTO Guide, is the procedure most commonly used today for concrete overlay thickness design. The MEPDG, and more precisely, the recently released DARWin-ME program, is being implemented by numerous states. Finally, ACPA’s BCOA method is presented to address the unique behavior of thinner-bonded concrete on asphalt. The technical summary is expected to be released later this year.

As state transportation agencies and roadbuilders grapple with the persistent economic concerns, a growing number of them are increasingly turning to concrete overlays to provide high-quality, durable, sustainable and economically-viable solutions. For more information on concrete overlays, visit acpa.org.

Concrete APPS

ACPA Apps can do a lot of work for you

By Robert Rodden, P.E.

Director of Technical Service and Product Development

American Concrete Pavement Association

It is the era of technological wonders in communication. Consider, for example, how smartphones are becoming dominant features of the communication landscape.

Keeping pace with this important technology wave, the American Concrete Pavement Association (ACPA) introduced its first web-based applications last November, and has since introduced more than 40 web-based tools, or web applications, via a special web portal, http://www.apps.acpa.org. ACPA has released new iPhone and iPad applications.

The web apps are divided into several categories including some general interest apps, design apps, and construction and pavement analysis tools, as well as interfaces to design software. Although these apps are germane to concrete pavement placement, repair or preservation, many of these web-based tools are more general and will help people with broader construction interests.

One very popular web app is ACPA’s National Concrete Overlays Explorer at http://www.apps.acpa.org/apps/OverlayPass.html. The exploration begins with a map featuring push pins, and adjacent to it, a sidebar menu of project details that serve as filters. By activating a push pin or selecting from the sidebar menu, the user can view project construction details, photos, performance information and much more. The app is designed to answer questions agencies, consultants and contractors have about key project details, for example where concrete overlays have been used and how they have performed.

The general-interest apps include a database of state agency practices, a glossary of concrete pavement industry and general transportation-construction terms, a units converter with many industry-specific conversions not included in other online converters, and other useful tools that can benefit construction professionals on the grade or in the office.

Design apps include a bonded concrete overlay on asphalt thickness designer. Developed by ACPA with support of the Federal Highway Administration (FHWA), the National Concrete Pavement Technology Center (CP Tech Center) and the Illinois Center for Transportation (ICT) at the University of Illinois at Urbana-Champaign (UIUC), this application is based primarily on the results of FHWA-ICT-08-016, “Design and Concrete Material Requirements for Ultra-Thin Whitetopping.” This is the formal name of a research project conducted in cooperation with the ICT, the Illinois Department of Transportation (IDOT) and FHWA.

The online thickness designer allows pavement design professionals or others with engineering expertise to enter general design factors, existing pavement structure details, concrete material details and factors related to the concrete overlay to determine the necessary bonded concrete overlay thickness.

Among the 18 design apps are a Westergaard stress and deflection solver, a compression seal joint width calculator and an online thickness designer based on ACPA’s popular StreetPave software for conventional jointed plain concrete pavements. Also included is an online k-value calculator, as well as an equivalent single axle load (ESAL) calculator that allows users to estimate future or historic traffic counts.

Construction and pavement analysis tools include an extremely popular evaporation rate calculator; a strength converter that converts between compressive, flexural, split tensile strengths and modulus of elasticity; a pavement joint noise calculator, and a concrete temperature calculator. Users also can find highway specifications used in airport pavement applications, calculate area and volume, determine staking intervals and the maximum recommended joint spacing, and perform more than a dozen different construction and pavement analysis operations using ACPA’s web apps.

In the pavement design software section, there are interfaces to evaluation versions of ACPA’s StreetPave roadway pavement design tool, WinPAS roadway pavement thickness design and evaluation tool (based on the 1993 AASHTO Design Guide for Pavement Structures), AirPave airport pavement design tool, and the newest design tool in ACPA’s software suite, PerviousPave, a pervious concrete pavement design tool. The pavement design software section also includes links to:

• COMPASS: computer-based guidelines for job-specific optimization of paving concrete. This tool is currently under review by the FHWA and is not an official set of guidelines, yet. When accepted by FHWA, it will result in a truly performance-driven mixture design system.

• HIPERPAV III (HIgh PERformance Concrete PAVing) software, developed by the Transtec Group for the FHWA, and used to analyze the early age behavior of jointed concrete pavements continuously reinforced concrete pavements and bonded concrete overlays.

• EverFE 2.24, a 3-D finite-element analysis tool used for simulating the response of jointed plain concrete pavement (JPCP) systems to axle loads and environmental effects. EverFE was jointly developed by the Universities of Maine and Washington with funding from the Washington and California State Departments of Transportation.

• And DowelCAD 2.0, a software program created collaboratively for optimization of dowel bar design. The software also allows engineers to determine joint responses to varying dowel sizes or investigate the impact of various alternate dowel bar configurations and shapes.

Moving Ahead

Keeping pace with web-based technology also means meeting the growing demand among smartphone users. ACPA has developed a number of iPhone and iPad apps, and continues to monitor use of other platforms, including Android, with an eye on further development to meet demand. The current list of ACPA’s iPhone and iPad apps includes:

Area and Volume Calculator: An app that allows users to quickly calculate plan area and volume of material based on a pavement or subbase/subgrade layer’s thickness, width and length.

Evaporation Rate Calculator: This app uses the evaporation rate equations in Paul Uno’s ACI Materials Journal article, “Plastic Shrinkage Cracking and Evaporation Formulas,” (July/August 1998). The equations are based on the popular evaporation rate nomograph from ACI 305R, Weather Concreting. Using this tool, users can quickly calculate the evaporation rate at hourly intervals based on concrete temperature, air temperature, ambient relative humidity and wind velocity.

Concrete Mixture Proportioner: Provides a method of proportioning a concrete mixture using the absolute volume method in substantial conformance with ACI 211.1-91, “Standard Practice for Selecting Proportions for Normal, Heavyweight and Mass Concrete.”

Maximum Joint Space Calculator: Allows users to calculate joint spacing in jointed plain (unreinforced) concrete pavement.

Staking Interval Calculator: Calculates the rate of change of a vertical curve and, based on this value, provides maximum staking interval recommendations.

Subgrade Resilient Modulus Calculator: Based on the conversion factors included in NCHRP Report 128, “Evaluation of AASHTO Interim Guide for the Design of Pavement Structures,” this tool allows users to quickly estimate the Subgrade Resilient Modulus (MRSG) from either a California Bearing Ration (CBR) or Resistance Value (R-value) measurement.

Joint Noise Estimator: An app based on the work of acoustics expert Dr. Paul Donavan, Sc.D., a senior scientist at Illingworth and Rodkin. This tool allows designers to estimate the impact of various joint geometries and condition on the overall tire-pavement noise level. It may also be used to guide pavement maintenance efforts in terms of the noise-related benefits attainable from sealing joints.

These mobile applications are available in Apple’s iTunes App Store store (http://www.store.apple.com/) for a nominal fee. Users of iPhones and iPads who click on the iTunes App Store link on the ACPA App Library site will be taken directly to an application purchase site; all other users will be directed to landing pages that describe the product and include ordering information.

For additional information about the ACPA web apps and links to software programs, contact the author at 847.423.8706 or rrodden@acpa.org. v

Ward Nye, president and CEO of Martin Marietta Materials, says in the MMM earnings report that “despite a continuing difficult operating environment,” he is pleased with the company’s performance.

“That we were able to increase prices and control costs is a credit to our operating teams and our disciplined approach to managing our business,” Nye says in a written statement about the earnings. “Specifically, in the quarter, aggregates pricing momentum continued with a 2.6% increase in the average selling price of our heritage aggregates product line. The quarter was, unfortunately, challenged by erratic weather as well as reduced spending on infrastructure projects. Therefore, as has been the case in the recent past, volumes were significantly lower, and that had an attendant negative effect on our operating profits. Our Specialty Products business continued its exceptional performance and established new quarterly records for both net sales and earnings from operations.”

NOTABLE ITEMS (ALL COMPARISONS, UNLESS NOTED, ARE WITH THE PRIOR-YEAR QUARTER)

– Earnings per diluted share of $0.78 compared with $1.18.

– Consolidated net sales of $426.7 million compared with $442.8 million.

– Heritage aggregates product line pricing up 2.6 percent.

– Heritage aggregates product line volume down 9.3 percent.

– Heritage aggregates product line direct production costs down 2.5%, despite a 13 percent increase in energy costs.

– Specialty Products record quarterly net sales of $49.6 million and earnings from operations of $19.3 million with a 380-basis-point improvement in operating margin (excluding freight and delivery revenues).

– Consolidated selling, general and administrative expenses down $1.9 million, or 20 basis points as a percentage of net sales.

– Consolidated earnings from operations of $63.0 million compared with $b90.7 million.

– Acquired an aggregates, asphalt and ready mixed concrete business in San Antonio.

‘Back to gravel’ doesn’t have to be the only choice for a failing road … even if funds are scarce.

By Mike Anderson

Ken Skorseth isn’t down on asphalt; he’s up on options for cash-strapped agencies facing expiring or deteriorating secondary roadways.

And, for a guy who’s been at the “Alternatives to Paving” table for at least a decade, he’s suddenly seen the spaces around that table fill up and overflow with hungry transportation engineers and planners.

“Number one, what’s driving this is economics. The rapidly escalating prices of highway construction and maintenance and the essentially flat budgets in local transportation is the first reason this is happening,” says Skorseth, program manager of the South Dakota Local Transportation Assistance Program. “But the second reason, and it’s huge for us in the Central Great Plains region, is the dramatic increase in the size of trucks and ag equipment, and that goes right along with the graphically increased yield of our crops, our grains. And then a third factor is that so many of the local roads are at the end of their design life.

“It’s all hitting us at once.”

Notice Skorseth uses “Alternatives to Paving” – which is also a title in his presentations – as compared to the industry movement’s more common refrain of “Returning to Gravel.” The latter connotation, he has come to understand, has painted him in some circles as an anti-asphalt guru of sorts. Returning the lowest-volume roads to stabilized gravel is an option – and a sound economic one for agencies, he says, as long as the road retains a low volume – but it is not the only option Skorseth offers. Some choices do, in fact, include the use of asphalt:

An asphalt surface treatment – not pavement but rather prime/chip – placed over a deep aggregate base. This is referred to as “blotter” in South Dakota.

Put to work widely in Australia, New Zealand and South Africa, a tactic that has caught Skorseth’s eye involves “building almost all of our structural strength to carry loads in a prepared subgrade and in base layers, and then simply constructing a very thin asphalt treatment at the surface – really nothing more than weatherproofing. It’s thin and it’s fragile, but will work if indeed you build all the structural strength to carry the loads underneath it.” This technique has promise here, he says, but admittedly “is a hard sell in North America, because our concept of a deep base layer falls short of what is needed to do these for a long life cycle.”

Using a 20-year lifecycle cost, a study conducted for the South Dakota DOT summarized that, for roads with up to a 170 ADT (average daily traffic) rating, a stabilized gravel surface is suitable. That threshold, says Skorseth, falls to 150 ADT if user costs are factored into the math. “If it goes higher than that, it’s not a good economic decision to go to gravel only, because the loss of gravel from high volumes of traffic and the frequency of maintenance needed will exceed the cost of pavement, if you calculate a lifecycle,” he says. “Of course, trying to find the upfront money to rehabilitate or reconstruct the asphalt surface is the big hurdle. That’s a lot of money at once.” With a gravel road, the initial cost may not be as high, but the maintenance is.

“It’s a catch-22 [telling an agency] to go back to gravel, but be prepared to do stage construction – ‘and hopefully you can find the money to eventually get this back to a pavement’ – with base improvement to handle today’s traffic,” says Skorseth.

Blotter, the South Dakota study concluded, is suitable up to approximately 650 ADT. Other options cited by Skorseth include:

incorporating chloride (magnesium or calcium) in to a minimum 2 to 3 inches of the layer, not solely on the surface as traditionally used for dust control;

using geosynthetics as part of the base construction; and

“in somewhat of a lost art,” incorporating a natural binder, usually highly plastic clay, into the top 2 to 3 inches. Bentonite has been used as a natural binder in Montana, western North Dakota and bits of Wyoming, he says.

A Warning Flare

Whether or not they are on the same side of the table as Skorseth in solutions, asphalt paving industry officials share many of the same concerns and observations.

“Many states have had ‘Farm to Market’ programs for quite some time. Their intent in general was to provide higher-quality routes for farmers or ranchers to market places or primary state routes,” says Mike Kvach, the National Asphalt Pavement Association’s vice president, product deployment. “Over the years, changes in the economy, the size of farm equipment and haul loads, etc., have impacted these pavements in various ways. The use and need for the route might have diminished and/or agriculture equipment increased the impact and deteriorated the pavements, and now there just isn’t any dollars to maintain these routes.”

“. . . right now, the DOT and the counties and the cities for that matter are just doing their very best to just hold on by their teeth.”

- Bill Rosener, executive vice president, Asphalt Paving Association of Iowa

That some road agencies are contemplating or perhaps even enacting a back-to-gravel solution “is to me a warning flare from these agencies saying, ‘Let’s put our heads together and see how we can save our roadways,’” says Kvach. “I don’t think any agency wants to take out a perfectly good roadway, but rather, ‘What can we do short of just turning the darned thing into gravel or turning and walking away from it?’ There are other strategies out there, and a lot of the agencies may not be fully aware of all of the strategies available.”

The Asphalt Paving Association of Iowa (APAI) sits down with consulting engineers and with officials at the counties and cities “to provide them with best and most cost-effective ways to rehabilitate roads,” says Bill Rosener, APAI executive vice president, explaining that rehab often requires 4 to 5 inches of overlay, but that budget-tightened agencies are actually doing 2 to 3 inches “just to get them by. Even when they have some money to do rehab, they’re not doing it to the level that they really need to or should do, because they can’t.”

The secondary roads most vulnerable to cost cutting often have a sealcoat surface, “a liquid asphalt with chips applied across top, which is OK for very low maintenance,” says Rosener. “Eventually, they need to do some hardsurfacing with an asphalt overlay. These roads are well-suited for that, but the people just haven’t had the money to do it. If you don’t keep up with the chip seal or overlay with asphalt, eventually it begins to break down and turn back into a gravel road.”

A Supporting Cry

If county or state agencies do decide to turn paved roads back to gravel, or perhaps more accurately simply allow this to occur somewhat naturally, they’re not going to receive any heat about it from the industry most negatively affected by such a decision. Conversely, they’ll receive nothing but sympathy from the asphalt paving sector.

“You bet I feel for them,” says Tom Gaetz, executive director, Washington Asphalt Pavement Association. “Here in America, how would we ever imagine that we could have roads being converted back to gravel because we don’t have the money to maintain them as paved surfaces?”

As with Gaetz in the Pacific Northwest, Rosener reports that such a movement is certainly not yet prevalent in Iowa, which has the 13th-longest road system in the nation, but that rumors and even anecdotal evidence suggest the practice is starting to occur in isolated situations.

“The bigger issue is that we just have a severe lack of funding,” says APAI’s Rosener, “and the counties are feeling it probably worse than anybody. There’s a severe need within our state.” A study done for the DOT in the early part of last decade indicated that Iowa needed to increase its funding for roads by $220 million annually, “just to maintain,” he says. A few minor revenue recommendations were adopted then, but the key one, an increase in the gas tax for the first time since 1988, was not. “That need’s just amplified since,” says Rosener, “and honestly, right now, the DOT and the counties and the cities for that matter are just doing their very best to just hold on by their teeth.”

There is, says Rosener, a faint glimmer of hope: As compared to his predecessor who was strongly against a gas tax increase, current Gov. Terry Branstad has appointed a committee to study the road funding shortfall and report back with recommendations by year’s end. “We’re certainly pressing for that,” says Rosener, citing a Reason Foundation report last September that ranked Iowa’s roads system 31st in the country overall. “Without any additional funding, we’re definitely going to be dropping in the ranks.”

In Washington state, Gaetz will continue to build coalitions to lobby for funding increases, based in part on past success. “When we ask for these increases, I have found that if we don’t have dedicated funds, we have lost the confidence of the voting public,” he explains. “So, one of our big deals here is that when we look at revenue packages, we identify defined needs.” A transportation gas tax increase was successfully passed in the state in 2005-06 after work by proponents included the development a list of 273 specific capital improvement projects. “We got $17 billion to address that project list,” says Gaetz, “and every one of those projects on that list is under construction and will be completed by the year 2016.

“We will have to do the same when it comes to road preservation and creating dedicated funds,” Gaetz continues, “so that they can’t be swiped away and put into general fund, which is the common practice of every legislature in the country.” The effort’s packaging, says Gaetz, will include educating the public on the difference between capital improvement projects and preservation projects, the latter having “clearly come to the top of the need list.”

Agencies in his state, operating on a solid pavement management program across the board, says Gaetz, “know where to spend the money. It’s just that they don’t have the money to spend.”

“The point would be, coming from the asphalt industry, that there are strategies that will help them retain a good roadway – a fair roadway anyway – and keep them in an asphalt program,” says Kvach, the former APAI executive now working at the national level with NAPA, “so that as the economy does return, there’s a good foundation that they can work from.

“Asphalt – and this is what I like about this industry – is a product that allows us to have all these strategies. When we say asphalt is flexible, sometimes we talk not just about the physical nature of asphalt, but its economic flexibility. We can take these various strategies, these various levels of implementation, and work with an agency to help them get to a certain goal . . . and find a long-term strategy that might work within a strained budget.”

Albeit from a different perspective, Skorseth has a similar objective. “Think big. We’ll survive, just not in the way we did from 1950 to about 2007,” he says.

“I’m not down on the asphalt industry. I’m just trying to help all of my local customers who just don’t have the money to build the strength on the surface anymore,” says Skorseth. “We have to recognize the fact that if we are going to help our customers, we’ve got to meet them where they are . . . and they don’t have an extra $3, $5 or $10 million to go out and rehab a lot of pavement.

“We’ve got to meet them where they are and see what kind of solutions we can come up with,” he says, “and that’s what we’re working on here.”

Dr. Don Brock

talks to John Latta, Editor-In-Chief

Dr. Brock, a Ph.D. in mechanical engineering from Georgia Tech where he once taught thermodynamics, is chairman of the board and chief executive officer of Chattanooga, Tenn.,-based Astec Industries, a company he founded in 1972. There are now 16Astec companies producing asphalt mixing plant; asphalt pavers; asphalt milling machines; asphalt heat transfer vehicles; soil remediation machinery; aggregate processing equipment; and pipeline and underground utility construction equipment.

What is your reaction to the Administration’s goal of making ‘livability’ a core transportation value?

Livability makes my blood boil. Our mobility is our freedom . . . I don’t think most Americans connect to that. We can go where we want to, when we need to. Look at the roads in Russia, the total miles and the quality of the roads and you see people there do not have that freedom. Thinking about roads should stay that simple.

Will we reach a point where we start losing the battle to maintain our highways?

I think we’re there. We have a plant in Wisconsin and I was up there recently and there are roads in that state you can’t drive on . . . I didn’t think it would come to this, but we’re going to have to do it at a state level. I think our federal government is just too dysfunctional . . . A lot more money is collected at the state level and it’s starting to make sense to me.

Reauthorization?

I think what’s missing is a vision. People will follow a vision, but they won’t follow little programs aimed at maintaining roads. A vision for a new system, a new way of doing things, would get American people excited.

A vision such as . . . ?

Ideally I’d like to see our highways with four lanes for cars and four lanes for trucks. If we took trucks off some lanes, they would last three times longer, they would stay smoother and we would have fewer accidents . . . If we added 15 or 20 cents to the fuel tax, we could build those lanes. The savings from fewer fatalities and less fuel used because ofsmoother roads and longer road life would pay for that tax increase. We could use a different structure for the truck lanes to make them last longer and stay smoother too . . . A dime in gas tax would add about $75 a year to the average driver’s budget and I think the public would go along with that if you had a visionary plan run by people they could trust.

New moves at Astec?

We have more than 20 new products coming out. Since so many of our customers have concrete and asphalt plants, they have asked us to start building concrete plants. They will be highly mobile, they’ll set up onsite and you can pump it. You won’t need ready-mix trucks . . . We’ve made some really beautiful mixes already . . . we can measure the water content on the fly and you dial in the slump. The quality of concrete going into roads today is terrible. And that starts at the quarry. We’ll screen the aggregate to size, blend it and mix it in a twin-shaft mixer. Seventy percent of our customers are in both concrete and asphalt, they have asphalt and ready-mix plants. If the cement and concrete people are going to push for more concrete roads, we’re going to be able to build them better. We started by using pieces we use in asphalt plants and repackaging them . . . then building new as required from there. My goal is a concrete plant and paver that could pave as smooth as asphalt. The key to that is the uniformity of the aggregate in the mix.

What’s the key to quality roads?

The key to building a good road is drainage, drainage, drainage. The key to the quality of the road you build on that base is uniformity, uniformity and uniformity. The strength comes from the way the aggregate interlocks, not the glue. The glue you use in the mix – be it asphalt or cement – is secondary. The top surface of the road is the roof. If it leaks (like the roof of your house), the base will be destroyed. Unfortunately, with concrete, the road leaks from day one at the joints. However, a flexible pavement will stay smoother and always last longer than a hard pavement because it does not require an expansion joint.

The Shuttle Buggy is something of an icon. What’s the story behind it?

It did things we didn’t think it did. We bought a German paver in 1981 and had it in Georgia – that state had smoothness requirements even then. The paver had a 12-inch-wide screed and the angle was steep. We were leaving bumps a show dog couldn’t jump over when it stopped and started again . . . we had surge bins at the plants. So I had the idea that if we could make one that worked onsite, we wouldn’t have to stop; it would be continuous paving, so no bumps, and fewer trucks. I drew it and took it to 12 customers. No one wanted it. We finally got an order and we built it. The first sketch of mine did not hold enough mix, and to make more room, we changed the auger design so it could hold enough to do the job we designed it for. We actually used an old screw auger from a hot storage bin my father had built years before . . . We found out later that the design also remixed the aggregate and fixed the separation problem . . . then later than that, we found it also remixed cold and hot asphalt and got rid of the problem of temperature variations and cold spots in the mat. We’re building the concrete transfer machine with that auger. Better lucky than good.

The asphalt vs. concrete debate?

When you get all of the emotion out of it, then it’s clear it’s not all that competitive. Today 80 to 90 percent of asphalt is going into the top 2 inches of roads, and concrete can’t compete there. But asphalt can’t compete in the buildings and nonroad markets. So really the only head-to-head competition is for new roads, and that’s only 10 to 20 percent of the total market for both of them . . . We all work for the traveling taxpayer and we should build them the best-quality roads we can. If the agencies choose concrete, we need to make it as good as we can.

You have a number of companies, and you are very decentralized in management. They work almost independently of central direction. Why?

You get a very narrow product focus, and you get pride of ownership and authorship.

Rollers compact the 50-percent RAP mat on Manitoba PTH 8.

Half and Half

One year later, a mat with 50-percent RAP looks really good.

by P. Michael Harnsberger,

Western Research Institute

All photos courtesy of Western Research Institute.

A stretch of asphalt in Canada, laid down in September 2009, is beginning to reveal its secrets.

Initial tests on the road included examination of a section which used 50-percent Reclaimed Asphalt Pavement (RAP) provided by the old road it replaced. The first results are positive. And that’s good news to proponents of using higher percentages of RAP, a process which had environmental (fewer emissions) and budgeting (lower cost) plusses for road building.

In March 2009, the Asphalt Research Consortium (ARC), consisting of the Western Research Institute, Texas A&M University, the University of Nevada-Reno, the University of Wisconsin-Madison and Advanced Asphalt Technologies, met with Manitoba Infrastructure and Transportation (MIT) to discuss research being conducted by the ARC and the desire of MIT to incorporate “green” technologies into its asphalt paving construction. The ARC was working on a five-year research project funded by the Federal Highway Administration (FHWA) with significant emphasis on “green” technologies like higher levels of RAP, warm-mix technologies, and cold-mix technologies.

Fig. 1 Gradation of the Manitoba PTH 8 aggregate.

Both the ARC and MIT were interested in incorporating higher levels of reclaimed asphalt pavement (RAP) into pavements to reduce the cost of new pavement and to recycle the value and materials from the older pavements. Recycling of asphalt pavement into new pavement is not new, but using higher percentages of RAP in the surface lifts of pavement is not nearly as common. But constructing sections with high RAP content was not the only concern. MIT and the ARC wanted to monitor the performance of pavements to obtain valid data on the value of using d materials.

Designing the Road

In the early discussions, MIT was planning on using RAP on a 28.5-kilometer (about 17-mile section of Provincial Trunk Highway 8 from Gimli to Hnausa. The ARC was interested in using 50-percent RAP in the top two lifts of the pavement and providing asphalt binder and mix testing of the proposed materials prior to construction. MIT was also very interested and enthusiastic to try higher levels of RAP in surface courses and to have additional resources to help test and evaluate the materials. Since the old pavement on the project highway was being completely removed, it was advantageous to be able to use all of the available old pavement in reconstructing the highway. The final plan for the RAP pavement sections included a section with 50-percent RAP, a section with 50-percent RAP and a softer grade of asphalt, a section of 15-percent RAP, and a section of conventional hot-mix, all of which were to be constructed in sequential pavement sections in the same project using the same contractor and the same materials. The plan allows for a direct comparison of the effect of RAP on pavement performance.

The hot-mix plant used on the Manitoba RAP project. The bin on the left was used to add RAP to the mix.

The MIT project personnel conducted mix design testing of the four proposed mixes and provided materials to the ARC members at the University of Nevada-Reno (UNR), the University of Wisconsin-Madison (UWM), and Western Research Institute (WRI). The MIT mix designs adjusted the aggregate gradation to account for the gradation of the RAP at both the 15-percent and 50-percent levels. In some cases where high RAP content is planned, it is recommended that the RAP be fractionated into coarse and fine fractions using the ¼-inch sieve. Because high RAP content paving mixtures are not common in Manitoba, the contractor was not required to fractionate the RAP into coarse and fine fractions.

RAP stockpile used on the Manitoba RAP project.

The mix designs used the Marshall mix design method with a target air void of 4-percent, 5.1-percent asphalt content, and 13-percent voids in the mineral aggregate (VMA). The geology of Manitoba, being mostly an ancient lake bed, makes it challenging to economically use substantial quantities of rock. Therefore, most of the aggregate gradations are on the finer side of the maximum density line and manufactured sand is used as a method to attain VMA. A plot of the Manitoba aggregate gradation is shown in Figure 1.

The UNR team and the WRI team also tested and characterized the asphalt cement planned for the project. Manitoba is fortunate to have only one source of asphalt (one crude oil source) for its projects, and the asphalt has historically provided good performance so testing of the asphalt cement before construction was almost certain to represent actual construction. The project asphalt was designed to be a 150/200 pen asphalt from the McAsphalt Industries terminal in Winnipeg. The softer grade planned for one of the 50-percent RAP sections was also supplied by McAsphalt and was a 200/300 pen asphalt. The UNR team performed Superpave binder testing on the two asphalt samples. The 150/200 pen asphalt graded as a PG 58-28 with the continuous grade being a temperature of 136.0° F. and -25.96° F. The 200/300 pen asphalt graded as a PG 52-34 with the continuous grade being 129.38° F. and -29.92° F. In both cases, the low temperature value was controlled by the bending beam stiffness value and not the slope of the creep stiffness value (m-value).

In many other cases, the low temperature grade is determined by the m-value. Research at WRI has shown a correlation between the crystallizable fraction of straight-run asphalt and the low-temperature controlling value with the low crystallizable fraction asphalts having the low-temperature specification limits controlled by the stiffness value. Asphalts that have a higher-crystallizable fraction have the low-temperature specification value controlled by the m-value.

The UWM and UNR teams used the pre-construction materials provided by MIT in the development of a new RAP mortar test to evaluate the properties of the virgin/RAP binder blend without using a solvent extraction. RAP mortar is defined as RAP material that passes the Number 50 sieve and is retained on the Number 100 sieve. The sieved RAP material is mixed with fresh binder at the desired concentration and a beam of material is prepared in a standard bending-beam mold. Using the BBR data from the fresh binder and the data from the BBR beam including RAP, the effect of the RAP on the low-temperature grade can be determined. A similar procedure can be used using the dynamic shear rheometer (DSR) to determine the effect of RAP on the intermediate and high-temperature properties. More information on the ARC testing and research can be found at the ARC website, www.arc.unr.edu.

Construction of the sections commenced in September 2009. The construction consisted of two 50-millimeter lifts of each of the four materials. A 1.3-killometer length of each material was constructed with great attention to ensure that the correct material was placed in both lifts in the correct locations. It was an important requirement of the project to have a substantial length of each material to allow the production equipment to attain a smooth and continuous processing environment for the temperature and production rate. Another aspect of the 1.3-killometer pavement length was to have enough length to plan and establish two 500-foot performance-monitoring sections in each material.

Documenting Construction

During construction, personnel from MIT and WRI were present to document mix-plant conditions, placement location of materials and sampling of paving materials. Another goal of the project was to collect substantial quantities of the construction materials for testing of the as-constructed pavement and also to collect large, but reasonable quantities of construction materials for storage at the FHWA Materials Reference Library. Storing construction materials provides an opportunity to conduct testing on these materials in the future if new performance-related tests are developed. MIT and WRI personnel collected approximately 26,000 pounds of loose mix, 6,000 pounds of aggregate and RAP; and about 250 gallons of asphalt cement.

The UNR team is conducting tests on the plant-produced mixtures for moisture damage, permanent deformation (rutting), fatigue cracking and thermal cracking (transverse cracking). The mixes are tested for moisture damage using the multiple freeze-thaw procedure outlined in AASHTO Method T-283. The permanent deformation testing is evaluated using the repeated load triaxial test in the Asphalt Mixture Performance Tester (AMPT). The fatigue cracking propensity of the mixes is being evaluated using the flexural beam fatigue test, AASHTO T321-07. The thermal cracking properties of the RAP mixes are measured using the Thermal Stress Restrained Specimen Test (TSRST), AASHTO TP10-93.

Results of the testing to date indicate that the four mixes (three containing RAP, one hot mix) will perform adequately. One of the main goals, if not the largest goal, of the project for both the ARC and MIT is to compare the laboratory testing with actual field performance.

Measuring Performance

Following completion of construction, WRI and MIT personnel established two 500-foot performance monitoring sections in each of the three RAP and one hot-mix sections (eight monitoring sections). The sections were established and the initial monitoring used the FHWA Long-Term Pavement Performance (LTPP) guidelines and protocols. MIT personnel conducted Falling Weight Deflectometer (FWD) and Longitudinal profile testing of the sections for baseline data.

Subsequent LTPP protocol distress monitoring will be conducted annually on the 500-foot sections by the ARC. Distress documentation will follow LTPP protocol. Core samples will be obtained annually to examine the physical and mechanical properties of the pavements by the UNR team. The WRI team will use the core samples to assess the extent of aging in the asphalt and the effect of the RAP on aging.

The first annual performance monitoring of the Manitoba RAP sections was conducted in October 2010. As should be expected, all of the sections are performing well and no distress was noted.

Data gathered during the life of this project will help determine the value of using RAP and help the asphalt community learn how to use high levels of RAP in the most effective manner. MIT and the ARC expect this to be a long-term relationship. v

Diamond milling teeth making a case

By Daniel C. Brown, Contributing Editor

Chewing up old asphalt is tough on teeth.

Replacing teeth on a milling machine is a time-consuming process, but it’s a job that must be done regularly as milling machines do their work. Standard tungsten carbide teeth last from a few hours to a few days, depending on the material they’re working in.

But now millers have a new set of teeth to choose from, with the advent of polycrystalline diamond teeth. And they’re showing that they last many times longer than conventional teeth.

“Depending on the abrasiveness of the aggregate and the hardness of the asphalt, our teeth will last from one month to 40 weeks,” says Jeff Crockett, business development manager for Novatek (novatek.com), the Provo, Utah-based R&D company developing the new teeth. “We’ve had some teeth last for a year.”

Sure, but how much do they cost? “The diamond teeth are very expensive – they would cost in excess of $100 per tooth,” says Crockett. “So, during the product development phase, we lease them on a tonnage basis – contractors pay us by the ton for the teeth.” He says that the lease price is determined so that Novatek can recover some of the development cost yet still save the contractor money compared to buying standard teeth.

Man-made diamond milling teeth last longer.

The teeth, now in a trial marketing phase by Novatek, have been tested by some 15 to 20 contractors in 10 states and in Europe in the Netherlands, Crockett says. More than 6 million square yards of asphalt have been milled with the new diamond teeth.

Wade Bortell, a superintendent with Mill-It Corp., a large milling contractor in Altamonte Springs, Fla., has fitted nine of his milling machines with the diamond teeth and plans to outfit a 10th machine. “We’ve got some mills out there with 1,000 hours on one set of diamond teeth. If we have 10 milling machines with these teeth, I think that speaks for itself. Our crews like them. They’re not on the ground changing teeth all the time. We just don’t have the downtime we would have with carbide teeth.”

The key material in the new teeth is polycrystalline diamond that starts out as a diamond powder. Novatek uses a high-temperature, high-pressure process to fuse the powder into a solid mass and on to the tungsten carbide base. The highly wear-resistant diamond offers benefits to milling contractors that include a more efficient operation, reduced fuel consumption, less wear and tear on the milling machines, and a more consistent and better quality road surface that is attractive to departments of transportation, says the company.

There are two designs of the new teeth. One design fits the Kennemetal, Sollami and Caterpillar holders. A second smaller design fits a Wirtgen-style drum.

“Right now, there’s a sticker shock over the price of these teeth – but the value more than compensates for the cost,” says Crockett. v

High-tech materials, mobile equipment can keep potholed, cracked pavements in use longer.

By Tom Kuennen, Contributing Editor

Potholed, cracked or delaminated pavements are so common that they can be easily overlooked. That’s until driver complaints spur reaction, or until it becomes apparent that the pavement has decayed so much that it’s no longer worth remedial maintenance spending.

By that time, it will be no longer worthwhile to put any more money into the pavement to attain a serviceable condition. Having fallen off the “preservation curve,” during which maintenance funds will substantially extend the pavement’s service life, the pavement will have to be rebuilt at much greater expense than if periodic preservation had been provided (see adjoining page).

Classic “throw, roll and go” patching is a time-honored solution to pothole repairs.

Fortunately, a variety of pavement preservation tools exist – among them, new high-performance patch materials for asphalt and concrete pavements, and self-propelled pothole patching machines – that are making the preservation of potholed and distressed pavements, well, less distressful.

Pothole Patching Today

Historically, filling potholes might have needed a truck and a crew of maintenance workers, who would place a few tons of material per day. The “throw, roll and go” paradigm – in which workers toss shovels of hot- or cold-mix asphalt into a pothole, the rear tire of the truck backs over the pothole, and everyone moves on to the next pothole – no longer need be the norm. That’s because new methods automate this process with great improvements in productivity.

At the same time, the longevity and quality of pothole patch materials has gotten better. And with mobile patching equipment, even though more expensive equipment is required, agency work forces no longer are exposed to traffic in a moving work zone.

With higher cost materials, pothole patching should be considered an investment, rather than a quick fix. The material used should be selected on the basis of where a pavement fits into a pavement inventory and pavement management system (PMS). If a pavement is so far gone that it is ready for reconstruction, the least expensive material likely is the best for emergency repair.

By applying pavement maintenance at frequent intervals, existing pavement (green) condition can be prolonged over many years (blue), as opposed to letting the pavement decline over years to a point where major expenditures are required (red).

Ultimately, the issue boils down to available funds. The road industry and owners know how to build long-lasting roads, but they usually don’t have the funds to build the longest-lasting pavement. Instead, a road may not be constructed to optimal standards, and then the pavement may not be maintained in a timely manner that will prolong pavement performance. Potholes and other surface distresses can be the result.

The right choice of patching material should be determined after study, because pothole repairs should be an engineered process. Emergency repairs may use a material – such as hot- or cold-mix asphalt – that can hold for 48 hours to three months, perhaps until late spring. But other materials, when cured, can be far stronger than the existing pavement matrix, with the possibility that the pavement can disintegrate from around the patch, with the patch material still intact.

What is a Pothole?

The Federal Highway Administration defines a pothole as a bowl-shaped hole in the pavement surface, of various sizes, with a minimum width of 6 inches. Low-severity potholes are less than 1 inch deep, moderate from 1 to 2 inches deep, and high severity greater than 2 inches deep.

Patching will work only so long; this county road in central Illinois will receive a complete foamed asphalt recycling.

Potholes in asphalt pavements always are associated with HMA fatigue damage and water damage, and the worst potholes appear in late winter or early spring, depending on the climate, after a series of freeze-thaw cycles.

As Sunbelt agencies will attest, cold winter climate isn’t necessary to form potholes. Water enters the road base through surface cracks or from the sides of the road, and water can become trapped in small voids beneath the pavement surface. This water saturates and compromises the base. As vehicles run over the surface and the saturated base material, the unsupported surface layer is forced down, displacing the saturated layer and causing a hole. This hole gets larger as vehicles strike the hole and begin to pull existing pavement out of the depression.

But icy weather exacerbates the pothole. During the winter, the water freezes, which draws more water into the base material. February and March freeze/thaw cycles result in frost heaves, which let in more water. Then the ice melts from the top down, leaving a trapped pool of water. Again, traffic strikes the hole and breaks it open.

The time that the worst potholes appear is not the best time to be making permanent patches with conventional materials such as standard hot or cold mix asphalt. But use of high-performance bonding agents or patching materials can result in a durable patch whether the hole is wet or the patch is executed in below freezing temperatures.

Choices of Repair Materials

Most agencies have three types of cold mixes available to them, reports the FHWA in its guide, Materials and Procedures for Repair of Potholes in Asphalt-Surfaced Pavements: Manual of Practice (Google FHWA-RD-99-168). “The first of these is cold mix produced by a local asphalt plant, using the available aggregate and binder, usually without an opportunity to consider compatibility or expected performance.”

High-performance, proprietary repair materials can be placed in cold, wet conditions and still perform to spec.

Use of such a mix in late winter or early spring would probably be a stop-gap measure until weather improves. In winter, such material congeals and is not easy to work with, while in summer the material is fluid and sticky.

“The second type is cold mix produced according to specifications set by the agency that will use the mix,” FHWA said. “The specifications normally include the acceptable types of aggregate and asphalt, as well as acceptance criteria for the agency to purchase the material. The aggregate and asphalt usually are tested for compatibility before specifying acceptable sources.”

The use of pothole repair spray-injection equipment (see below) by agency forces would fall into this category, as the agency must check the asphalt-aggregate compatibility before placing patches, FHWA said.

“The third type is proprietary cold mix,” FHWA said. “A local asphalt plant generally produces this material using specially formulated binders. These binders are produced by companies that test the local aggregate, design the mixes, and monitor production to ensure the quality of the product. These materials (like other cold mixes) can be produced in bulk and stockpiled, or they can be packaged into buckets or bags to make the material easier to handle in the field.”

Spray-injection patching performed by a contractor would fall into this third category, as the aggregate and binder are supplied by and should be tested by a patching contractor, FHWA said.

Premium National Brands

High-performance premium national brands constitute another type of cold patching material. One such proprietary cold mix product is UPM Permanent Pavement Repair Material from Unique Paving Materials Corp. This high-performance material, the manufacturer states, can be applied any time of the year in any kind of weather conditions, including wet and freezing.

As illustrated in these pictures (from top to bottom): existing damaged pavement; repair is squared, cleaned of debris and tacked; and final repaired pothole.

For placement, an application area should be swept of debris. The material then is shoveled or poured into the pothole from bags, pails or drums, and compacted. No primer or tack coat is required, UPM says.

UPM claims that over 90 percent of repairs using its product will outlast the surrounding pavement. The product is supplied in seasonal grades, matched to local aggregates, with specific formulations to accommodate year-round patching needs. And as it’s supplied premixed, UPM says, there is no need to visit the asphalt plant and wait in line.

A competitive product is HP Asphalt Cold Patch from Crafco Inc. HP is approved as a high-performance patching material in most states, and other user agencies, within the United States, Crafco says. Like the UPM product, HP is specifically formulated for the wide-ranging temperatures and climates of its market areas. This permanent repair works in all weather conditions; wet, cold or hot, the maker says.

HP is supplied in bags, and no mixing, mechanical compaction or tacking is required. The material, Crafco says, permanently adheres to asphalt, concrete or steel, thus is applicable for bridge, drain, utility cuts and cutter work. The patch can be opened to traffic immediately, the manufacturer says.

Bonding Agents for Wet Conditions

If a lack of funds forces an agency to eschew proprietary mixes, and use conventional cold mix asphalt to patch potholes, it has the option of using a sprayed bonding or contact agent to ensure attachment to the wet substrate.

One such product is Bondade from Transpo Industries, Inc. Bondade is a solution which promotes adhesion of asphaltic materials to a variety of substrates. The coupling agents in Bondade markedly extend the working life of asphalt repairs by securing a firm, water-insensitive bond between repair asphalt and the base materials, Transpo says. “Bondade should be used whenever new asphalt or bituminous concrete is applied to either concrete, asphaltic surfaces or potholes,” the maker adds.

This bond will last up to 85 percent longer than conventional methods, the maker says. It’s an environmentally-safe “green” product, which is non-toxic, non-flammable and non-combustible, and contains no volatile organic compounds. It’s indicated for hot and cold patch repairs, damp or dry holes, overlays, cold joints between lanes of HMA, and emergency repairs, Transpo says.

Spray-Injection Uses Crew of One

A step up from the truck-and-crew methods are the self-propelled units. The spray-injection patching process using a mobile unit reduces personnel used to one worker. For example, with the Rosco RA-300 unit from VT Lee-Boy, Inc., one person controls all patching functions from the cab.

This hydraulic “patch-on-the-go” system permits patching of large numbers of patches on the move in a single day, with no auxiliary power. The driver operates a joystick from the driver’s seat and performs a four-step process, typically in less than a minute per repair, the maker says.

During the patching process, a robotic patching boom extends and retracts while on the move, with the operator’s joystick controlling boom movement. At a repair, the pothole is cleaned with a high-volume blower, and a tack coat of emulsion is sprayed. A mixture of aggregate and hot emulsion then is injected into the pothole, which is followed by a finish coat of dry aggregate. Traffic can resume at once.

On the Rosco RA-300, a pressurized flow system minimizes maintenance with only one moving part, the maker says. Delivering the air, aggregate and emulsion needed in the spray patching process is a low pressure (3 to 4 psi) system that keeps material flowing into the air stream and eliminates the need for moving parts. A 5-cubic-yard aggregate hopper and 400-gallon emulsion tank allows the unit to patch for days, requiring only occasional aggregate fills.

Lower Costs with Patch Trucks

While less sophisticated than the robotic spray-injection units, an all-in-one pothole patch truck may help an agency lower personnel costs associated with pothole repair. For example, the Town of Irondequoit, N.Y. is aggressively fighting potholes using a self-propelled electric-heated pothole patching truck that has improved road conditions while optimizing safety and cutting costs.

“It’s very important that the taxpayers of this town are pleased with the services we provide for them,” said Jeff Graves, labor foreman for Irondequoit Department of Public Works. “We are a diverse and established town, and nobody likes to drive over or around potholes. Our flameless pothole patcher has proven to help us keep up with the volume of potholes and has significantly increased our patching quality.”

In the winter months, when HMA wasn’t available, Irondequoit used a cold-patch material and the “throw, roll and go” method. When HMA was available, the town would travel with just enough material to fill the open excavations and major patching areas. But the HMA would cool quickly and at times the crews were not able to use all of the purchased asphalt.

The town looked for a more efficient method to preserve the hot asphalt. Irondequoit had used a propane-operated patching unit, but when it was time to replace the unit, Graves looked elsewhere because he wanted something that could keep the asphalt material warm for a longer period of time. The town settled on purchasing an FP5 Flameless Pothole Patcher from Bergkamp, Inc.

The most significant element of the new unit is the electric-heated hopper that keeps the asphalt material warm while the unit is in motion or stopped. It uses an onboard hydraulic-powered AC generator to heat its insulated

5.1-cubic-yard hopper, and keeps the material at a consistent temperature throughout the day.

In addition, Graves and his crew use the tools on the unit to follow a process for most potholes. The damaged pothole area is squared off using an attached hydraulically-driven pavement breaker. The old material is then removed and placed into one of the spoils bins, located on the side and rear of the truck so workers can safely stay out of traffic’s way.

The combination compressed air and tack coat wand blows the remaining debris out of the pothole. The same self-cleaning wand then applies the warm tack coat. The ability to dispense warm tack coat in any weather condition has been a huge factor in prolonging the life of Irondequoit’s repairs.

An auger dispenses material onto the swivel material chute, which delivers the fresh, hot asphalt to the prepared area. The chute slews left or right, allowing for multiple pothole and shoulder repairs from one location. Finally, a hand-operated plate compactor – or single-drum roller – will vibrate and compact the material flush with the existing pavement.

Graves estimates he is saving up to 10 man-hours some weeks producing new patches, instead of performing repetitive repairs. The town has also lowered material costs. With the propane-operated pothole patcher, the town was unable to productively use approximately 10 percent of the hot asphalt material purchased per week. At an average of $67 per ton last year, the town saved approximately $200 per week.

In addition, by making fewer trips to the asphalt plant, the town saves on diesel fuel costs, wear and tear on the equipment and has increased on-the-job productivity. And Graves doesn’t have to worry about purchasing costly heating oil or propane anymore. He just turns the unit on and the onboard hydraulic-powered AC generator provides power to the full-length electric-heating elements. The elements produce a consistent heat from the front to the back of the patcher, eliminating hot spots and the need for heating oil.

Infrared Offers Option

A different approach to permanent patch repairs is the infrared option. Distressed pavement surface repairs – such as potholes, alligator cracking, bird baths, high spots, pavement seams, manhole covers or failed repairs – may be effectively fixed using the infrared process.

Seamless infrared asphalt repairs are achieved by using specialized equipment to heat the existing asphalt surface to a depth of up to 3 inches. New hot mix asphalt is then mixed with the existing asphalt, forming not a patch, but a seamless repair that is thermally bonded to the surrounding asphalt. After a slurry or chip seal, the repair likely will not be detectable.

The seamless repair will resist water intrusion, can be performed in any weather conditions or temperatures, and can be opened to traffic in an hour or less in most cases.

After a repair area is cleared of broken and raveled asphalt, an infrared heater is positioned over the repair area, which is then exposed for up to 10 minutes. After the asphalt is softened – but not scorched – a lute or rake is used to define the outer edges of the patch. At least 6 inches of the heated surface should remain undisturbed around the outside edge of the patch, contractors say. The rake is then used to scarify the inside of the hot patch area and an asphalt rejuvenator is mixed with the raked, aged asphalt.

Then, fresh virgin asphalt is added to the site to bring the repair up to grade. The patch is then leveled with a lute and the area around the repair is swept clean. Compaction flush with the surface completes the infrared repair.

Concrete Pavement Repairs

Spalled concrete caused by fatigue, freeze/thaw cycles, warping stress, ingress of water, or substrate problems can lead to costly reconstruction, and repairs require a different approach than with flexible pavements. But patching of portland cement concrete (AC) pavements with conventional PCC – with its long cure times and lane closures – can cause excruciating user delays, whether on an expressway or airport runway.

As conventional rigid cement repairs – such as epoxies or fast-curing cementitious products – often fail due to de-bonding, fatigue and differential expansion characteristics, additional cracking and the need for repeated repairs may occur. Instead, a variety of high-performance concrete patch materials provides quick repairs that not only cure very fast, but solve long-term patch durability issues.

For example, TechCrete from Crafco provides a long-term solution for distressed concrete pavement preservation, the maker states. It’s a hot-pour repair solution which provides flexibility, high-tensile strength, the ability to bridge joints, and high compressive resistance, the maker says.

Once in place, a TechCrete patch will move with the pavement and will not de-bond or crack, Crafco says. The product also has a high friction surface ideally suited for thin bond repairs, multi-corner slab repairs, joint intersection repairs and recessed applications. Repairs with Crafco TechCrete can be opened up to traffic within as little as one hour.

Another product, Rapid Set from CTS Cement Mfg. Corp., is a specialty cement which gains structural strength in 1.5 hours after placement, materially reduces drying shrinkage, and reduces porosity for enhanced durability. It results in a workable, 5-inch slump concrete that gains compressive strength of 2,500 to 3,000 psi in 1.5 hours. The shrinkage of Rapid Set concrete is about 25 percent of the shrinkage of same slump portland cement concrete.

Its improved durability by reduced porosity is demonstrated by superior freeze-thaw resistance, the maker says. This attribute makes it ideal for placement where speed and durability is of the essence, for example on night patching on urban expressways or bridge decks, or night runway repairs at major airports, where liquidated damages for failure to open can run into the tens of thousands of dollars.v

Both processes derive their momentum from severely sinking state revenues coupled with the lack of a six-year highway bill from Washington which is keeping available funds at an level inadequate to even maintain existing roads.

Both processes help address the funds shortage. But while we see the need for them don’t forget a very old rule of political thumb: reversing practices like these when times are better is no slam dunk. We are liable to see gravelled rural roads and toll booths still being created long after the economy has recovered.  Just as we will surely hear some Washington politicians telling us that since there are now less paved roads to maintain, and since there are more income-providing toll booths, states and other agencies responsible for roads ands bridges don’t really need new money as much as they used to.

Anyway, check out USA Today’s story on the states fervor to toll.

Granite’s share of the contract is 45 percent, or about $47.7 million. Granite will book the project into backlog during the second quarter of 2010.

Led by Granite, CHC includes Kiewit and W.W. Clyde. The team is responsible for the construction of nine miles of a two-lane road between Redwood and Old Bingham Highway. All nine miles will be asphalt paved in a frontage road alignment. Work will include signalized intersections, recreational trails, drainage improvements, and new structures.

CHC was awarded the construction management (CM) portion of the contract in the fall of 2009 and has been working closely with UDOT and the project designers throughout the design, constructability and cost estimating phases. CHC is currently working with UDOT and the project designers in a CM capacity for an additional general contractor (GC) package.

Some initial early work is already underway and will be completed in December 2010. The current GC contract is estimated to be completed by the fall of 2012.

For more information, go to UDOT’ Web site at www.udot.utah.gov/mountainview.