Field tests show that the Next Generation Concrete Surface is competitive with the quietest pavements available.

In the past decade or so, environmental noise has become a major issue in many parts of the world, including the United States. Stakeholders ranging from the general public to the roadbuilding industry have expressed concerns over highway noise. Recognizing that highways are a factor in urban noise, the concrete pavement industry set out to research and develop quieter pavements without compromising performance, durability, safety or other inherent benefits of concrete.

NGCS pavements have been placed with either a single-pass or double-pass operation by the grinder, and both work equally well.

In recent years, the concrete pavement industry has developed a Next Generation Concrete Surface (NGCS). With field tests indicating sound levels of 99 to 101 decibels, these diamond-ground surfaces are producing results that are very competitive with the quietest pavements available, says Larry Scofield, P.E., Director of Pavement Innovation for the American Concrete Pavement Association (ACPA).

Sound testing is conducted using the On Board Sound Intensity (OBSI) method, which allows assessments of acoustic performance of pavements over time. The method was developed by General Motors and introduced to the highway community by the California Department of Transportation. More about the NGCS follows:

The background

Research showed that much of the perceived problem with concrete pavement’s noise results from a pure tone, or “whine” that occurs when noise with a certain discrete frequency emanates from the tire/pavement interface. Almost always, those frequencies were set with concrete pavement by uniformly-spaced transverse tining.

In an effort to improve pavement safety, the FHWA in the late 1970s had mandated transverse tining, and many states complied. Then in 2005, FHWA dropped the requirement for transverse tining, and opened the door to other concrete pavement texture treatments. California, for example, had used longitudinal tining for more than 30 years and reported few if any problems with it.

Recognizing the worldwide interest in quiet pavements, in 2004 ACPA, with support from the cement industry, developed a program to research the noise characteristics of concrete pavements. A primary objective was the evaluation and development of a quieter concrete pavement surface. Also providing support for the program were the International Grooving and Grinding Association (IGGA) and several of its members.

Purdue University’s Ray W. Herrick Laboratories conducted the research using its Tire Pavement Test Apparatus (TPTA). The machine consists of a 38,000-pound, 12-foot-diameter drum that makes it possible to test numerous pavement textures and compositions in combination with various tire designs. Six curved test sections of pavement fit together to form a circle around the vertical edge of the drum. Two tires, mounted on opposite ends of a beam, are then rolled over the test samples while microphones and other sensors record data. The TPTA has been described as a “noise microscope” for tire-pavement noise. Tire speeds of up to 30 mph can be tested.

Scofield says the Purdue diamond grinding research was based on theories that the blade- and/or spacer-widths might be the keys to a more quiet pavement surface. But after evaluating the range of blade and spacer widths requested by the industry, Purdue reported that no unique relationship could be found between sound levels and spacer width, blade width and spacer/blade configuration. Instead, it appeared that the controlling variable – where sound was concerned – was the variability in the fin profile height resulting from the grinding process. The fins are the tiny vertical ridges that appear on a diamond-ground concrete surface.

Textures with low variability were quieter than textures with high variability. In conventional diamond grinding, the resulting fin variability is influenced by the blade/spacer configuration, the concrete mixture, aggregate type, pavement condition, equipment set-up and more. Because the fin variability occurs in the field, it is difficult to adjust in a laboratory setting. Researchers decided to grind a pavement smooth, then impart additional texture by grooving, which provided an exact fin profile that could be controlled and predicted.

An epiphany

A conventional diamond-ground surface produces texture in the upward or positive direction, while the texture tested at Purdue produces texture in the downward or negative direction. “The texture, which later was called the Next Generation Concrete Surface (NGCS), was desirable from the standpoint that it was more of a ‘manufactured surface’ and thus could be controlled as necessary on an experimental basis,” says Scofield.

The Next Generation Concrete Surface is competitive with the quietest pavements available.

“When these new textures were tested on the TPTA, they produced the quietest diamond ground surfaces,” Scofield says. “This was an epiphany in the research because it verified, for the first time, what the controlling factor was for tire-pavement noise generation of diamond-ground surfaces.

“The point of the NGCS surface is to limit positive or upward texture,” Scofield explains. “The NGCS texture is designed to develop good macro-texture through ‘negative’ or downward texture (grooves). We want to have both good microtexture (the texture on top of the lands), and good macrotexture, which is developed primarily through the grooves.

“The NGCS is quieter because it relies on negative texture and not positive texture,” Scofield continues. “Since it is more of a manufactured surface, it can control the fin profile to a greater degree than previously possible. Purdue University determined that the fin profile is the critical element in noise generation.”

A new reality

The epiphany in research was soon confronted by reality, Scofield says. Research showed that the flush-ground-then-grooved texture could produce a quieter pavement. But the research could not verify whether such a texture could be constructed with conventional equipment in the field.

Next, in response to industry representatives, researchers developed two methods of reproducing the NGCS. The first was a grinding head configuration that used three smaller blades stacked between two taller blades. That pattern was repeated across the grinding head. That way, in one pass the head could grind the surface smooth and also groove it on approximately ½-inch centers in one pass of the machine. The smaller blades would flush grind the specimen and provide microtexture while the taller blades created grooves.

The second grinding configuration used the same smaller blades to flush grind the pavement in one pass. Next a second pass using taller blades with spacers created the grooves, similar to what was constructed with the single-pass operation.

That way, contractors could choose either option – the single pass or the double pass – in field construction. Some industry representatives thought the single-pass operation would cause excessive blade wear and have the potential for ruining the head and blades. Many believed the two-stage process would be required. Today, this is not a concern. NGCS pavements have been placed with a single-pass or double-pass operation, and both work equally well.

Field trials

The opportunity to construct field test sections became a reality when the Minnesota DOT allowed construction of test sections at the MnROAD Low Volume Road Test Cell Number 37 as part of an FHWA pooled fund effort. The two Purdue surfaces were to be compared to a conventional diamond grinding surface to assist in determining the benefit achieved by controlling the fin profile. So, there was a need to build three test surfaces.

This first-pass, flush-ground surface on I-355 in the Chicago area shows up as the whiter strip on the pavement.

Findings validated that the newly-developed surface was quieter, at the time of construction, than the conventional diamond ground texture. And, findings showed that the Purdue TPTA results could be reproduced in the field using conventional equipment. But because those were not full-width text sections, the next step was to construct a full-width test section using a conventional diamond grinding machine.

The first opportunity to construct a full lane-width test section occurred on Interstate 355 in the Chicago area. In October 2007, both a conventional diamond-ground test section and an NGCS were built on the I-355 tollway. The sections were 1,200 feet long and one lane wide.

Scott Eilken is the owner of Quality Saw and Seal, the diamond grinding contractor for the NGCS section at I-355. He is an ACPA member, a board member of IGGA, and was instrumental in writing the specifications for NGCS.

“On I-355 we did one pass to flush grind the surface, and the second pass as surface grooving,” Eilken recalls. “When we first tested it, the surface produced just 99 dB(A). We were one of the first concrete pavements in the nation to get below 100 dB(A), so it worked pretty well.”

The next opportunity to build test sections occurred at MnROAD’s Interstate 94. A two-lane wide by 500-foot-long section of NGCS was constructed in a single-pass operation on a 14-year-old random transverse-tined pavement in October 2007.

With the successful placement and performance of the two mainline sections, the ACPA officially named the texture as the Next Generation Concrete Surface (NGCS). The name describes a category of textures that evolve for both new construction and rehabilitation of existing surfaces.

“The desirable characteristics of such textures will be predominately negative texture coupled with good microtexture and excellent macrotexture,” says Scofield. NCGS can now be found at seven sites in five states. There are three test sections near MnROAD; one in suburban Chicago; one in Norman Okla.; one near Abilene, Kansas; and one near Omro, Wis.

Other test sections have been established this year in Washington state and in Arizona.

All surfaces are still performing as intended. As of 2009, ACPA’s figures show that OBSI testing was conducted on 288 pavement sections consisting of 126,720 lineal feet (24 miles) of concrete pavements across North America. The surfaces were evaluated with two goals in mind; first, to benchmark current surface texturing practices, and second, to develop insight into the acoustic longevity of textures. The acoustic longevity will become increasingly important as quiet pavement technology becomes integrated into noise mitigation.

Recent sound results from the MnROAD test sections indicate that NGCS pavements are running in the range of 99 dB(A) to 101 dB(A). By comparison, conventional diamond ground sections ranged up to 104 dB(A).

One test section in Kansas shows that an NGCS surfaces has produced 99 dB(A) and 100 dB(A) in two different tests. By comparison, an Astro-Turf drag surface ranges up to 102.5 dB(A) and an exposed aggregate surface ranges up to 104.5 dB(A).

A renewable surface

At MnROAD, Diamond Surface Inc. constructed a surface casually called NGCS LITE, which was designed as a renewable surface. It was developed to provide additional microtexture on existing NGCS surfaces if the need arose to do so. With the large land size (between the grooves) of the NGCS surface, the texture wear has been assumed to be less than for a conventional diamond-ground surface. So, NGCS is expected to have a long life by comparison. v

by Daniel C. Brown, Contributing Editor

In association with ACPA

(American Concrete Pavement Association)

How the Mechanistic-Empirical Pavement Design Guide Helps Optimize Concrete Pavements

The M-E PDG can account for numerous variables in concrete pavement design

In its simplest terms, concrete pavement design optimization considers the performance benefits of various components versus their cost.

Design optimization can be thought of in various ways, says Michael Ayers, PhD, Director of Education for Design and Construction at the American Concrete Pavement Association (ACPA). Those include:

Achieving long life;

Lowering initial cost;

Minimizing maintenance and rehabilitation costs; and

Developing a sustainable, environmentally-sound pavement system.

Until recently, pavement designers were mostly limited to the 1993 AASHTO Pavement Design Procedure. Although many agencies are still using the 1993 protocol, it has limited inputs and is not ideal for optimizing pavement design.

Concrete pavement design optimization considers the performance benefits of various components versus their cost.

By contrast, the current AASHTO Interim Mechanistic-Empirical Pavement Design Guide (M-E PDG) has many more input parameters, which allow designers greater influence over pavement performance. The M-E PDG combines empirical or observed pavement performance data from a number of sources – primarily the Long-Term Pavement Performance Studies done under the Strategic Highway Research Program, and mechanistically-calculated pavement response parameters.

“When you combine those two elements, it gives you the flexibility to account for various types of design optimization,” says Ayers. The variables to be considered depend on the design method used in the analysis. The M-E PDG has the capacity to consider support conditions (including subbases for concrete pavement), concrete materials and properties, load transfer (both longitudinal and transverse), and numerous other criteria.

ACPA provides training programs in which designs are generated using the AASHTO 1993 guide, M-E PDG and StreetPave software, and are optimized for performance. Ayers says slab thickness is often used as a basis for comparison between design elements. However, says Ayers, it is preferable to compare estimated costs for the overall pavement structure including the subbase, load transfer, slab configuration, etc.

To establish a baseline design using AASHTO 1993, Ayers established the following inputs for an example:

Traffic: 20 million 18-kip rigid Equivalent Single Axle Loadings

Reliability: 90 percent

Concrete Modulus of Rupture: 600 psi

Concrete Modulus of Elasticity: 4.050 million psi

Load transfer coefficient: 3.2

Drainage coefficient: 1.0

Initial serviceability: 4.5

Terminal Serviceability: 2.5

Initial and final serviceability reflect the initial construction quality (primarily smoothness) and the end of the design life of the roadway (the point at which major rehabilitation or reconstruction is required).

With those inputs, AASHTO 1993 produces a calculated slab thickness of 11.5 inches. With AASHTO 1993, concrete strength and load transfer are important parameters. However, specific guidance as to the configuration of load transfer is not provided. Concrete durability and dimensional stability issues are also not addressed.

Many important design elements cannot be accounted for using AASHTO 1993. Simply altering traffic levels, reliability, support conditions, and levels of serviceability is not a true design optimization strategy, Ayers says.

Inside the M-E PDG

In 2008, the M-E PDG was adopted as an Interim Design Procedure by AASHTO. Full implementation by the states will take a number of years, and some states may not adopt it. The “final” version of the program, referred to as DARWin ME, is currently under development. However, the research grade software is available as a free download at (http://trb.org/mepdg/home.htm).

Ideally, optimization should be conducted based on a state or regional calibration of the M-E PDG. State or regional calibrations take into account such factors as climate and locally available materials.

The bases for comparison among the various design features are the three failure criteria for concrete pavements in the M-E PDG. The three criteria include transverse slab cracking, joint faulting and smoothness as determined by the International Roughness Index (IRI).

In his example of how M-E PDG works, Ayers includes the following variables:

Concrete strength;

Coefficient of thermal expansion of the concrete;

Subbase type and thickness;

Dowel bar size;

Edge support; and

Joint spacing.

30-year design

Failure criteria was set to the default values for cracking, faulting and IRI. Slab cracking was set at 15 percent; a faulting threshold of 0.12 inches was used; and terminal IRI was set at 172 inches per mile.

Those values, Ayers emphasizes, can have a significant effect on your final design. Establishing realistic failure values for a specific project is a key to successful use of the M-E PDG software.

Two primary climatic zones were analyzed in the example: Wet/freeze in Chicago, Illinois; and dry/no freeze in Phoenix, Arizona. Traffic was based on 5,000 AADT, and M-E PDG default values were used for traffic variables. Fully 100 percent of the design traffic was allocated to the design lane. The compound annual growth rate was fixed at 2 percent, and the design period was 30 years.

Next, Ayers chose suitable values for: soil type; granular subbases; concrete properties (modulus of rupture and coefficient of thermal expansion); dowel bar diameters and spacing according to ACPA guidelines; and edge support. A number of pavement configurations were evaluated, including the following: a 12-foot lane with no shoulder; a 13-foot widened lane; a 14-foot widened lane, and a tied concrete shoulder.

Graphs were developed illustrating the climatic effects on estimated transverse cracking, estimated faulting, and estimated IRI. In each case, the independent variable is shown as the slab thickness, and the failure mode is plotted as the dependent variable.

Similarly, the effects of base type on estimated transverse cracking, faulting, and IRI were plotted for various base types. Again, the independent variable is the slab thickness and the failure mode is shown on the vertical axis. For example, at a slab thickness of 10 inches, using a granular base in Chicago with 50-percent reliability, cracked slabs go to zero.

The effects of various modulus of rupture values, coefficients of thermal expansion, dowel diameters and spacing, and edge support were plotted to show what happens to the various failure modes for varying slab thicknesses.

Ayers says the next steps are to establish unit costs for the most likely design elements such as dowels, widened lane, treated versus untreated subbase type, and so forth. Designs that meet specified criteria – specifications, design standards for the type of pavement structure being constructed, materials availability, etc. – are selected. An economic analysis is then conducted to select the “best” designs. The final step is to select the least-cost, best-performing option, and rerun the analysis on the selected design for verification.

The results

In Ayers’ trial runs of the ME-PDG, design thicknesses ranging from 8 inches to 12 inches met the established criteria depending on the design elements selected. An economic analysis would determine the optimal design elements to specify in the final design. For instance, the use of a 13-foot widened lane significantly improved performance and thereby lowered the required slab thickness. The economic analysis would then determine if the added cost of the widened lane was offset by the decrease in slab thickness and difference in anticipated performance. A similar analysis would be performed for each critical design element. The process can become somewhat complex when multiple variables are analyzed simultaneously, according to Ayers.

Conclusions

Design optimization can lead to cost savings and enhanced performance if correctly applied. In order to generate realistic design options, a relatively sophisticated design procedure such as the ME-PDG should be used. Although it is possible to generate comparable designs with the AASHTO 93 Guide, the limited number of variables and sensitivities make comparing options difficult.

Implementation of the ME-PDG is an important step in developing realistic comparisons between design options.v

by Daniel C. Brown, Contributing Editor

In association with ACPA

(American Concrete Pavement Association)

Massachusetts has saved nearly $12 million in the year-plus since it started using civilian flaggers to direct traffic at some road construction sites, state officials say, providing factual underpinning to what has become a hotly debated issue in the 2010 gubernatorial election campaign, according to the Gloucester (Mass.) Daily Times.

A job-by-job breakdown provided to The Associated Press shows how the state saved $28,000 during four relatively slow days in May by paying lower wages for flaggers to either replace or supplement the police officers who formerly had exclusive rights to stand watch over highway and side-road work zones.

Essex Police Chief Peter Silva said he’s still not convinced. “The savings that are being described may be mirage-like,” Silva said. “They are telling us that this is going to save us a substantial amount of money; I want to see where the savings are.” Silva also highlighted the dangerousness of the work, and the value of having extra police officers on the road. “It’s second to none having a police officer on a work site,” he said. “They have instant communication with the police, ambulance, and fire officials in our community, which the flaggers currently do not have.”

Police are still used exclusively in high-speed or otherwise dangerous locations.v

Fund Gap = Road Gap

A gap in funding will lead to a gap in a busy stretch of roadway in West Virginia, say state highway officials.

Officials with the Department of Highways are floating the idea of tolls to help fund the reconstruction of a 14.6-mile stretch of U.S. Route 35 from Buffalo to Henderson. The unfunded two-lane stretch lies between a completed piece of widened U.S. 35 and another portion slated for completion this fall. “As this gap section gets narrower and narrower, the issues of safety become more and more,” Greg Bailey, DOH director of engineers, told a public meeting in Winfield.

Between $200 million and $250 million is needed for the yet unfunded stretch, which has a long history of fatal accidents, says Putnum County Commissioner Steve Andes. “There’s more truck traffic on the stretch of road than I think on any other road certainly in West Virginia and the surrounding area,” he says.

DOH has yet to decide on a final funding package, says Bailey, but even with tolls, “the amount of revenues that appear we could generate is not enough revenue to complete the entire 15 miles of highway construction. We would have to take some of our normal construction funds and apply it to the project.” Without local tolls, the road would be built as funding become available, one mile at a time, DOH spokesman Brent Walker has said.

Some area residents attending the public meeting balked at the idea of having to pay $1-$4 to travel U.S. 35 each time out. “We’ve already paid for that road,” said Frazier’s Bottom resident Rob Logus. v

To The Editor:

Kirk Landers sure holds onto a grudge, doesn’t he? (“Failure to Bash,” July) Why else would he feel compelled to write today about events that happened almost a decade ago?

I can’t speak to Mr. Landers’ experience in 2001. I wasn’t with FHWA at the time, the current public affairs staff was not here, nor was our Administrator, Victor Mendez. Mr. Landers acknowledges an “aversion” for government employees, meaning the deck was probably stacked against any staff member he dealt with.

But beyond his personal experience, Mr. Landers raises questions about the role of FHWA, the professionalism of our communications staff and the quality of the information we provide the public.

FHWA works in partnership with the states to create a highway system that is second to none. Under the leadership of Administrator Mendez, we are constantly looking for ways to provide the best service to the American people. An experienced, professional communications staff – knowledgeable in everything from asphalt temperatures to work zone safety – works hard every day to help keep the public informed.

Administrator Mendez demands accountability and transparency in all aspects of our work. Our FHWA website is rich with information and our contributions to recovery.gov – the government’s web-site dedicated to the Recovery Act – include contract data, pictures and descriptions of projects, even interviews with workers.

It would be hard to find a federal agency that provides more information than we do.

Again, I can’t speak to events that may or may not have taken place nearly 10 years ago. What I can tell you is that the people of FHWA work tirelessly to enhance safety, improve our infrastructure, strengthen our economy and create jobs. Perhaps it’s time Mr. Landers stops holding onto 10-year-old encounters and starts focusing on 21st century transportation opportunities.

Cathy St. Denis

Associate Administrator for Public Affairs

Federal Highway Administration

Feds fund streetcar revival

The Obama Administration has provided $300 million to, as Secretary of Transpiration Ray LaHood puts it, expand the Administration’s livability initiative agenda, to fuel economic recovery for local communities

The funds, being made available through two competitive grant programs, the Urban Circulator Grant Program and the Bus and Bus Livability Grant, mean that “residents in dozens of communities nationwide will soon enjoy major transit improvements, including new streetcars, buses, and transit facilities.”

The investment, actually $293 million, is part of the Obama Administration’s livability initiative to better coordinate transportation, housing and commercial development investments to serve the people living in those communities, said the secretary.

“This investment by the Obama Administration in our nation’s communities will create jobs, boost economic development and recovery, and further reduce our dependence on oil,” Secretary LaHood said. “Our goals are to provide cleaner, safer, and more efficient ways to get around.”

Six new streetcar and bus rapid transit projects will be funded with $130 million from the Federal Transit Administration’s Urban Circulator Program, and 47 additional projects aimed at upgrading bus services and facilities are slated to receive more than $163 million from the Federal Transit Administration’s Bus and Bus Livability Program.

“Streetcars are making a comeback because cities across America are recognizing that they can restore economic development downtown – giving citizens the choice to move between home, shopping and entertainment without ever looking for a parking space,” said FTA Administrator Peter Rogoff. “These streetcar and bus livability projects will not only create construction jobs now, they will aid our recovery by creating communities that are more prosperous and less congested.”

The six cities that submitted successful Urban Circulator proposals include Dallas and Fort Worth, Texas; Chicago, Ill.; St. Louis, Mo.; Charlotte, N.C.; and Cincinnati, Ohio. The six projects were selected from 65 applications totaling more than $1 billion in requests. Construction of bus facilities and new bus and bus-related purchases will move forward in the 31 states where 47 Bus and Bus Livability projects are located. These projects were selected from 281 applications totaling over $2 billion in funding requests.

The Obama Administration’s Livability Initiative is a joint venture of the U.S. Department of Transportation, the U.S. Department of Housing and Urban Development, and the U.S. Environmental Protection Agency. Projects were eligible to receive up to 80 percent in federal funding, with a maximum of $25 million for Urban Circulator projects.

Fill ‘er up!

It seems like a fair question. If hybrids run on electricity (and only electricity, not the ones that also use gasoline) should owners contribute fuel taxes when they fill up? Especially when stimulus dollars are involved.

There are more than 200,000 electric hybrids on America’s roads relying on internal generators. A relative handful get their power by plugging into an electric outlet. [Should they be called hybrids if they are all electric?] In the fourth quarter of this year, with much fanfare, both Nissan and Chevy will roll out new plug-ins.

But you don’t just pull into any old gas station to refuel if you are away from home. Today there are approximately 450 public electric refueling stations out there. Millions of dollars from the American Recovery and Reinvestment Act (ARRA), that is, ‘stimulus’ money, has been handed out to two companies that deal in public refueling stations for plug-in electric vehicles.

Some new owners will get free charging stations, worth more than $2,200 thanks to the stimulus grants. The idea is that data recorded by stations will help the efficient future development of public charging stations nationwide.

kirk.landers@att.net

When I became the new editorial director of Better Roads in 2001, I made a pilgrimage to the Federal Highway Administration to tap into the agency’s vast resources of information and expertise.

The experience was a lot like gorging on Chinese food — post meal bloat followed by pangs of starvation. A professional PR guy introduced me to a half dozen executives and loaded me with 10 or 20 pounds of FHWA publications. It seemed like an embarrassment of riches, but when I sorted through the publications, only a few brochures bristled with the kind of hard facts I was seeking. The rest of the literature seemed to use hundreds of words and precious few facts to cover things like road building and safety in ways that would not offend anyone, while also not informing anyone of anything they didn’t already know.

I took solace in having expert contacts in all the right places in FHWA, but that turned out to be a limited benefit, too. A couple years later, I scheduled a series of meetings with FHWA personnel to learn about trends in the road and bridge industry. The afternoon before the scheduled meetings, an agency PR person called to emphatically inform me that I had committed a nearly treasonous breach of FHWA security by scheduling these meetings without the sanction of an official FHWA PR person. Not only must an official FHWA PR person set up such meetings, I was told, the official PR person must be in the room at the time the meetings occur.

Naively, I told the official PR person I would be delighted to have her sit in on all the meetings. Of course, being an official PR person, she already had commitments for the next day and the next week, and no surrogate could sit in for her. My information tour would have to be rescheduled for some time in the future. The distant future.

I have an aversion to bureaucrats, so I never again tried to deal officially with FHWA. I was able to gain some insights by speaking informally with FHWA experts at various industry functions they attended without professional PR people shielding them from unwashed muckrakers like me, but I always felt like a great information resource was being withheld from the road industry and the trade press for no other reason than bureaucratic excess.

In the months and years since then, each time I have encountered a state DOT employee who seems to have an anti-bureaucracy, small-government bias, I ask that person if they think FHWA is worth whatever it costs to have it. I focus on these people because they are the most likely to give me a candid, negative response.

To my surprise, every single person has answered yes, FHWA is worth having. While this is a sample of just seven or eight people, they all had experience working with FHWA, and they all disliked big government and bureaucracies. Several had to think about it for awhile before responding, but each of them told me that FHWA plays an important, behind-the-scenes role in coordinating road programs in the U.S. and advancing new concepts in technology and best practices . . . in addition to administering the spending programs put into law by Congress.

I confess to being disappointed at this outcome. It pains me to acknowledge the worth of an organization that has so little regard for my own enterprise. However, my concession is limited. I still think the communications side of FHWA needs a robust audit to see if it is performing any useful function to the country or the road industry. And I still think at least one of the agency’s official PR people should know the difference between asphalt and concrete, should drive to work every day in a car, and should be aware of the existence of a trade press and how it differs from the Washington Post.v

New technology bringing new standards to measuring bridge conditions

By Tom Kuennen, Contributing Editor

“Smart” bridges are on the way for road agencies burdened with the responsibility of monitoring bridge conditions.

Not-so-old technologies like ground penetrating radar (GPR), acoustic emissions testing and lasers for bridge condition testing are being augmented with advanced mobile radar and laser technologies and today’s nanotechnology, which puts the science of bridge condition monitoring into a whole new era with products such as bridge coatings which can sense trouble within.

In the meantime, reliable, low-cost cellular phone service has lowered the barrier to remote reporting of bridge conditions, as battery-powered systems can “call in” condition reports to an agency computer and database or alert an agency if conditions change abruptly.

Today’s benefits can include better information about bridge conditions, a better database for National Bridge Inventory (NBI) reporting, and, long term, fewer demands on personnel for inspection. But field implementation depends on the ability to make high technology marketable in the field, and on the ability of cash-strapped agencies to pay for it.

Rewards, Barriers to Implementation

Nanotechnology is the latest permutation of bridge condition monitoring, but it caps a decade-and-a-half of activity in high-tech bridge condition monitoring.

“Advanced bridge condition monitoring techniques can provide quantitative condition measurements, as opposed to the subjective assessments that a visual inspector provides,” said Dr. Steven B. Chase, research professor of civil engineering, University of Virginia-Charlotteville Center for Transportation Studies, where he works following a 30-year career with the Federal Highway Administration.

“Many of the new methods can provide indications of conditions that exist prior to a visual indication,” Chase said. “And many of the technologies can measure things that simply aren’t visual.”

Current federal regulations require that a state conduct a bridge inspection every two years. With a total of about 583,000 bridges in the national inventory, in order to inspect nearly 300,000 bridges nationally with the amount of manpower that’s available, efficient and rapid assessments and inspections are required. Today’s new technologies can provide that.

But there are built-in barriers to implementation. Past data, and systems put in place to record the results of those inspections, have been predicated on use of visual inspection, not high-tech. “It will be a long time before these new technologies supplant or add a great deal of opportunity for an agency to save money,” Chase told Better Roads. “The case will have to be made that technology can provide better inspections, with a higher probability of finding a defect that could be significant.”

And staff will have to be trained, he said. “The use of all this technology does require a higher level of capability, training and experience that the typical bridge inspectors do not have,” Chase said. “We’re trying to change that by making the technology easier to use, and produce results that are easier to interpret. We want to change bridge management and inspection practices to integrate the kind of quantitative information this technology can provide, in a way that produces better decision-making. But we have been involved in this a long time, and it will evolve over time. I don’t expect any easy breakthroughs.”

Nonetheless, Chase and his fellow researchers have been fighting to bring the technology to the field. “We are working to bring this technology to bear, to make it easier to apply and to improve the quality of information that’s available to the bridge owners from inspections,” Chase said.

Focus: Decks and Superstructures

For rating and NBI purposes, states must collect condition data on a variety of bridge structural characteristics, including, according to Chase:

The bridge deck and all wearing surfaces

The bridge superstructure, including all primary load-carrying members and connections

The bridge substructure, including the abutments and all piers

Culverts, for culvert bridges, and

Channel and channel protective systems for all structures which cross waterways.

In addition to structural condition, bridge functional adequacy also is logged. This can include load carrying capacities, whether deck geometry or lane constrictions restrict safety, the presence of low underclearances that may result in detours, and the ability of the bridge to handle water flow rates.

Bridge condition technologies are centered on decks and superstructures, and much less on substructures. “Cracks in steel and concrete, damage from corrosion, all are areas in which various technologies are available for assessment,” Chase said. “There’s a lot of work on bridge decks and superstructures. By themselves, cables have been the focus of a lot of attention.”

But except for scour, the condition technologies available for bridge substructures tend to be focused on evaluating the quality of the substructure as it’s constructed, not after it’s in-place, said Chase.

“Evaluating the integrity of piles, drilled shafts and other substructure elements while they’re being constructed has evolved to the point where technology such as cross hole sonic logging and other methods are routinely employed to assess whether substructure elements are constructed properly,” he said. “But once the bridge is placed in service, we tend not to be too concerned with the substructure, with the one exception of scour. That’s because we tend not to have large failures of substructure elements; most of the collapses or other failures have been things that happen in the superstructure.”

Ground Penetrating Radar

Like with pavements, ground penetrating radar (GPR) has great applicability for studying bridge deck condition. GPR systems use electromagnetic radiation at microwave frequencies, and the radiation penetrates and characterizes concrete, while reflecting off metallic material like rebar. It has the potential to replace manual chain drag testing of decks, in which experienced staff listen to the sound the chain makes; ringing indicates a sound spot, while a dull thud indicates subsurface delamination.

A wireless sensing system from MicroStrain Inc., Williston, Vt., was installed on the I-95 Gold Star Bridge over the Thames River at New London, Conn.

The FHWA pioneered GPR for bridge decks by underwriting the development of the HERMES (High-Speed Electromagnetic Roadway Measurement and Evaluation System) product at the Lawrence Livermore National Laboratories in California. HERMES was intended to provide a GPR system that can reliably detect, quantify and image delaminations in bridge decks, at normal highway speeds, and was delivered in 1998.

“HERMES was a radar system that was much, much smaller than anything at the time was commercially available,” said Chase. “It had a much higher frequency, and was based on new technology that had been developed for producing extremely short, precisely timed pulses, which was created for Livermore’s work on fusion reactors. The integration of all of that into a system that employed computer-aided tomography, with an array of antennas, was a first.”

PERES/HERMES II system on Carter Creek Bridge, Dumfries, Va.

HERMES included a computer workstation and storage device, survey wheel, and control electronics, in addition to the array of 64 antenna modules or transceivers mounted in a towable trailer. To investigate specific areas of a bridge deck that require more detailed study, a single-antenna scanning device called PERES (Precision Electromagnetic Roadway Evaluation System) was developed as an extension of HERMES.

In mid-decade they both were supplanted by HERMES II/PERES, new GPR technology using a single transmitter and receiver antenna pair configuration, developed under a participating states’ pooled fund. Work using HERMES II/PERES incorporating other technologies continued into 2009 under the auspices of the University of Vermont.

A variation of this technology is the digital synthesis arrayed radar. HERMES and most radar systems employ a very short pulse, radiated into the deck as a very broad-band signal. “The pulses are on the order in picoseconds [one trillionths of a second], and the frequency content are in gigahertz [billions of cycles per second],” Chase said. “But they are very low energy, spread out over a broad band. Short wavelengths give you more detail, but don’t propagate very far into a material. Lower frequencies give you less resolution, but go deeper.

“What the digital synthesis radar does is, rather than rely on a pulse, it synthesizes [creates] a particular frequency digitally, and radiates that specific frequency,” Chase said. “By hopping or changing frequencies rapidly you can ‘interrogate’ the bridge deck, and it makes it easier to comply with prohibitions on intentional radiation of electromagnetic energy in certain protected wavelengths.”

Acoustic Emission Technology

Acoustic emission technology is a process especially suited for steel bridges, by which engineers “listen” for characteristic signals associated with cracks forming and extending.

“It’s used primarily for detecting and locating fatigue cracks in steel highway structures, and it’s a technology used in a variety of other industries,” Chase said. “When energy is released as a crack propagates, a series of stress waves are generated that can be detected with sensitive accelerometers, combined with sophisticated signal processing that separates those signals from the rest of the noise of a highway bridge.”

Acoustic emission technology is central to a new technology from the Center for Advanced Materials and Smart Structures at North Carolina A&T State University.

There, in 2007, Dr. Mannur Sundaresan, professor of mechanical engineering, developed a single-channel continuous sensor that has the potential to detect and locate early crack growth in structures, thereby providing timely information to prevent catastrophic failures. This single channel continuous sensor can detect the leading edge of the acoustic emission event, occurring anywhere in the region covered by the sensor.

Essentially, the technology involves using commercially-available sensors deployed in a unique configuration to acoustically monitor structural integrity to remotely detect and address standard flaws via acoustic emission signals.

According to Sundaresan, the technology operates like the body’s nervous system. “If you’re hurt, the nervous system lets you know right away,” he said. “That doesn’t happen with a structure. An inspector has to go look. With small cracks, it’s like finding a needle in a haystack. Small cracks are like cancer. They’re usually not noticed until they’ve grown large enough to cause serious damage. These sensors will detect the growth of cracks in their early stages just as our nervous system alerts us of any injury immediately so that we can take action to limit the damage.”

Smart Structures

Even as development of GPR and acoustic systems progresses, attention is shifting to how structures themselves may be outfitted to provide condition data. These “smart” bridges comprise an exciting new opportunity for advanced bridge monitoring.

Smart systems will have several advantages over GPR-based systems. They can provide information that is continuous and that takes place between survey visits. They can measure elements that GPR cannot measure, such as stress, strain, temperature, displacement and vibration, all of which are very useful in determining what is going on in a bridge structure. And they can measure performance instead of detecting damage, providing quantitative information, such as the scenario behind the generation of fatigue cracks.

“The definition of ‘smart structures’ has changed over time,” Chase said. “The National Nanotechnology Initiative has been important in producing new technology that can be turned into a sensor at a scale much, much smaller than before. And the new wireless communication technologies and miniaturization of computers are helping to bring the application of this sensor technology to civil structures. So it’s now possible to deploy multiple sensors – that are relatively small – that do not require much power and can more easily interrogate the structure at hand.”

For example, small, wireless sensors can be can be attached to bridge superstructures to measure variables such as strain, tilt, vibrations, temperature, and seismic activity. Using this technology, it’s possible to rapidly instrument a bridge at fatigue-prone or critical details, and measure what happens under traffic and wind loading.

Another example: recently a wireless sensing system from MicroStrain Inc., Williston, Vt., was installed on the I-95 Gold Star Bridge over the Thames River at New London, Conn. The sensors are powered via 6-in. by 9-in. photovoltaic panels, linked to rechargeable batteries which power microelectronic modules that record data from inside watertight enclosures. The data are wirelessly transmitted to an agency database. Because they are solar-powered, there is no need to manually replace batteries, a benefit as the sensors may be installed in hard-to-access places.

“Just the expense of running power cables to dozens or hundreds of sensors can be more expensive than the sensors themselves,” Chase said. “If we can get away from the need to have wires, and have inexpensive sensors that are compatible with wireless communication and data acquisition systems, and are tailored to the particular job they are asked to do, then it becomes economically possible to implement a system that will actually measure what’s going in multiple locations in a bridge in response to age, deterioration or traffic.”

The most common types of sensors will be battery-powered, with an emphasis on battery life. But they don’t have to be self-powered, as unpowered receiver-transmitter transponders also will do the trick.

“Wake-up” Sensors

“There is a new focus on sensors that will ‘wake up’ when you send them radio waves, measure conditions, transmit that data, and go back to sleep,” Chase told Better Roads. “These are best used for measurements that won’t change too much. But for conditions that are constantly under traffic, or wind loads, and continuous information is required, you will have to have a continuous power supply.”

‘Smart’ can apply to bearings as well. Smart bridge bearings take advantage of the fact that the distribution of live and dead loads to the bearings through the structural systems of the bridge can be used to diagnose problems.

Non-operating bearings and the tremendous stresses that result are a common factor in bridge failures and are a common maintenance requirement.

Multi-axis fiber optic strain sensors, capable of measuring both vertical and shear strains, are integrated into a composite panel. The panel then is laminated between the neoprene bearing pads commonly used on highway bridges, and will measure the vertical and lateral forces transmitted from and to the bridge.

Nanotechnology – and its application to bridge monitoring – constitutes the next frontier in smart structures.

Nanotechnology encompasses research, development and manufacture that utilizes and manipulates the unique properties of matter existing at the “nanoscale.”

At this length scale – approximately 1 to 100 nanometers, 1 to 100 billionths of a meter – clusters of atoms and molecules exhibit properties quite different from those found at larger scales. Thus, nanoscale science and engineering provide an opportunity to gain unprecedented insight into the unique phenomena existing at the nanoscale and to use that knowledge to engineer materials and devices with new characteristics.

With nanotechnology, super-small devices can be designed and manufactured to infinitesimal degrees of tolerance. Nanotechnology involves fabrication of devices with atomic or molecular scale precision, and at such a small scale, physical forces different from those of the ordinary human dimension are at play.

Today, nano- and micro-electrical mechanical systems (MEMS) sensors have been developed and used in construction to monitor or control the environmental condition, and the materials and structural performance. One advantage of these sensors is their small dimension; such sensors could be embedded into the structure during the construction process.

Larger than MEMS, “smart aggregate” has been used to monitor early age concrete properties such as moisture, temperature, relative humidity and early age strength development. The sensors can also be used to monitor concrete corrosion and cracking.

In a structural concrete matrix, smart aggregates can monitor internal stresses, cracks and other physical forces, and can be capable of providing an early indication of the health of the structure before failure can occur.

For example, researchers at Johns Hopkins University’s Applied Physics Laboratory developed a robust wireless embedded sensor suitable for long-term field monitoring of corrosion in rebar, particularly in bridge decks. These smart aggregate sensors can be embedded throughout a structure during construction, added to the mix right before placement. The smart aggregates are interrogated by a data reader that can be mounted on a car or truck; the transmitted energy from the reader excites the aggregates as it passes over them and collects their radiated sensor data onto a PC.

Each Johns Hopkins smart aggregate contains a wireless power receiver and data transmission coils, and incorporates ceramic hybrid integrated circuit technology to withstand mechanical stresses and concrete’s high pH environment. The aggregates are built to have a lifetime of 50-plus years.

“Nanotechnology will impact smart structures because the ability to manufacture sensors integrating nanotechnology gives us the potential to sense things that we could not in the past,” Chase said.

“For example,” he said, “there is work going on to develop chemical sensors that will serve as ‘artificial noses’, that can provide a very broad band of response to a variety of atmospheric gases. You can create a sensor that will be sensitive specific to a particular chemical, small enough that they will fit into a particular capsule, and mount that sensor on a structure. It then can tell you when the chloride ion concentration in the concrete has increased to the point where it might cause corrosion, but nondestructively, at a stage before there was any visible indication that damage had been done, with no inspector required to visit the bridge.”

Smart Bridges in Michigan

In early 2009, a new $19-million project on smart bridges was launched by the University of Michigan-Ann Arbor, with cooperation of the Michigan DOT.

The five-year project aims to create the ultimate infrastructure monitoring system and install it on several test bridges whose precise locations are not yet determined.

The monitoring system is envisioned to include several different types of surface and penetrating sensors to detect cracks, corrosion and other signs of weakness. The system would also measure the effects of heavy trucks on bridges, which is extremely difficult. And through enhanced antennas and the Internet, the system would wirelessly relay the information it gathers to an inspector on site or in an office miles away.

Funded in large part by nearly $9 million from the National Institute of Standards and Technology’s Technology Innovation Program, the project involves 14 UM researchers with the College of Engineering, and the UM Transportation Research Institute (UMTRI). In addition, engineers at five private firms in New York, California and Michigan are key team members.

The remaining funding comes from cost-sharing among the entities involved and the Michigan DOT. MDOT has offered unfettered access to state bridges to serve as high-visibility test-beds showcasing the project technology.

“This project will accelerate the field of structural health monitoring and ultimately improve the safety of the nation’s aging bridges and other infrastructures,” said Jerome Lynch, principal investigator on the project, and assistant professor in the UM Department of Civil and Environmental Engineering. “We want to develop new technologies to create a two-way conduit of information between the bridge official and the bridge.”

Four types of sensors will contribute to gathering data. Victor Li, professor of civil and environmental engineering, has developed a high-performance, fiber-reinforced, bendable concrete that’s more durable than traditional concrete and also conducts electricity. Researchers would measure changes in conductivity, which would signal weaknesses in the bridge. On test bridges, the deck would be replaced with this concrete.

A carbon nanotube-based “sensing skin” that Lynch and a colleague in chemical engineering are developing would be glued or painted on to “hot spots” to detect cracks and corrosion invisible to the human eye. The skin’s perimeter is lined with electrodes that run a current over the skin to read what’s happening underneath based on changes in the electrical resistance.

The sensing skin that Lynch and his colleagues created is an opaque, black material made of layers of polymers. Networks of carbon nanotubes run through the polymers. Carbon nanotubes are a fundamental building block of the nanotechnology revolution.

Each layer of the sensing skin can measure something different. One tests the pH level of the structure, which changes when corrosion is happening. Another layer registers cracks by actually cracking under the same conditions that the structure would.

The perimeter of the carbon nanotube skin is lined with electrodes that are connected to a microprocessor. To read what’s going on underneath the skin, scientists (or inspectors) send an electric current through the embedded carbon nanotubes. Corrosion and cracking cause changes in the electrical resistance in the nanotube skin. The microprocessor then creates a two-dimensional visual map of that resistance. The map shows inspectors any corrosion or fracturing too small for human eyes to detect.

Lynch says the skin could be a permanent veneer over strain- and corrosion-prone hot spots including joints on bridges, buildings, airplanes and even spacecraft. When it’s time to examine the health of the structure or aircraft, an inspector could push a button and in minutes, the skin would generate an electrical resistance map and wirelessly send it to the inspector.

Wireless Nodes

Also in the Michigan tests, low-power, low-cost wireless nodes could look for classical damage responses like strain and changes in vibration. These nodes would harvest energy from vibrations on the bridge or even radio waves in the air. They are being developed by Dennis Sylvester, an associate professor in the Department of Electrical Engineering and Computer Science, and Khalil Najafi, chair of the Electrical and Computer Engineering division.

The fourth type of sensor would be housed in the vehicles that travel on the bridge. UMTRI researchers will outfit a test vehicle to measure the bridge’s reaction to the strain the vehicle imposes. This information generally is not available today. But how vehicles, especially trucks, affect bridges is a critical piece of information that could help predict the structure’s lifetime.

Leading this effort is research professor Tim Gordon, head of UMTRI’s Engineering Research Division. “Our work will add to what is currently done, not replace it,” Gordon said. “The infrastructure problem and the feasibility of new monitoring strategies are emerging at the same time. We believe we have ways of testing the performance of bridges as integrated structures, not just inspecting their components.”

“The technologies from this project could prove very beneficial to the citizens of Michigan in the longer lasting, smarter, safer and ultimately more sustainable roadways,” said state transportation director Kirk T. Steudle, P.E.

Carbon Nanotubes at Work

Carbon nanotubes also will figure into two research projects announced in early April by FHWA. The project, under way at Florida State University, seeks to develop technologies to inhibit corrosion for new in-situ materials, and methods to repair or retrofit structures located both above and underwater. The research will utilize carbon nanotubes to develop an on-site spray-based method to develop both a structural capacity enhancement, and a barrier layer for corrosion resistance.

FHWA also issued a cooperative agreement for the University of Minnesota-Duluth to develop new, intelligent, self-sensing concrete pavement that can monitor its own structural health by continuously detecting internal stress level changes of the pavement. In the proposed pavement structure, the concrete will be mixed with carbon nanotubes, the piezoressitive property of which will enable the concrete to detect the changes in the mechanical stress.

Phase I of the proposed work will develop and test a prototype of self-sensing CNT concrete in a lab environment, and Phase II, which will be conducted in partnership of the Minnesota DOT, will fabricate and test the self-sensing concrete in a real but controlled road environment at the Minnesota Road Research Facility just north of Minneapolis.

Commercial Implementation

In the meantime, tried-and-true technologies like GPR are continuing to make their way into the field, but it’s only possible through improved technology.

“There are companies that will conduct a commercial GPR survey, and provide you with information that is based on more than just looking at echoes,” Chase said. “The work on phased array, on synthetic aperture, computer-aided tomography, and storing all this data on a computer and processing it to get information about what’s going on under the surface, all has evolved significantly in the last 15 years. A number of commercially-available systems have the capability of doing this type of signal processing, where it was not the case 15 years ago.”

And much more has transpired over the last decade-and-a-half. “The great thing is that simultaneous technological advances are making things possible today that weren’t possible just 15 years ago,” Chase said. “There have been tremendous advances in battery technology driven by the cell phone and wireless community that are now making it possible to have battery lives that are much longer than before. There also has been a focus on the development of low-power components, again, driven by the wireless technology industry, and they all have benefits for the bridge monitoring community.” v

Recycled concrete aggregate proves its value; but it demands an engineered approach.

By Tom Kuennen, Contributing Editor

Recycled concrete aggregate (RCA) is a valuable resource for road owners and builders, both in terms of lowering costs and in constructing a “green” highway. But RCA needs to be approached as an engineered product, with its production and reuse tailored to fit its composition and ultimate end use in a project.

Fortunately, new guidance is available that will help road owners and builders make decisions on how to use RCA, even as its utilization is growing on vast scales, for example the recently completed reconstruction and widening of I-294, the TriState Tollway in suburban Chicago.

Despite being blessed with extensive virgin aggregate sources, Texas is a strong supporter of RCA. In a September 2008 report, Recycled Concrete Aggregates Make ‘Cents’, the Texas DOT said, “In today’s environment of skyrocketing material and transportation costs encountered in road construction, recycled concrete aggregates (RCA) provide substantial savings to TxDOT and taxpayers.”

With RCA, natural resources are conserved, waste disposal is reduced, and air quality is improved due to reduced haul distances and reduced energy consumption, TxDOT said. “In many cases, allowing the use of RCA can be the most cost-effective choice for an aggregate source,” the DOT said. “This is especially true for those districts that do not have good, native aggregate sources. Using RCA can reduce time and expense of importing aggregates from other parts of the state.”

TxDOT has researched and used RCA with good success for about 17 years. In the years 2006-2008, TxDOT saved approximately 1.8 million tons of virgin aggregates by incorporating RCA in cement treated base, flexible base, continuously reinforced concrete pavement (CRCP), filter dams, gabion walls, concrete traffic barriers, flowable fill and select backfill for mechanically stabilized earth walls. “This equates to an estimated savings of $12.6 million from reduced or eliminated landfill and virgin aggregate associated costs. Savings from using RCA has the potential to increase tenfold based on current availability of RCA.”

RCA an Engineered Material

But care must be taken in specifying and using RCA in road structures and concrete mixes.

“Concrete pavement recycling is a viable, successful and proven technology,” said Mark B. Snyder, Ph.D., P.E., vice-president, Pennsylvania chapter of the American Concrete Pavement Association (ACPA), adjunct professor at the University of Pittsburgh, and 2010 president of the International Society for Concrete Pavements.

“However, RCA must be treated as an engineered material, and not as a straight-up replacement for natural aggregate,” Snyder told Better Roads. “The properties of recycled concrete aggregate can vary greatly, depending on the original aggregate source, and the production techniques. Therefore it’s necessary to characterize the material so it’s used properly, and if using in new concrete, appropriate adjustments are made in the structural or mix design.”

That’s why as an engineered material – like reclaimed asphalt pavement (RAP) – RCA must be tested and analyzed in a lab before being included in a structure or mix. In particular, the physical and mechanical properties of RCA vary with the quality and quantity of reclaimed mortar, which may affect the design of the structure or concrete mixture. These effects can be significant when maximizing reclamation efficiency by including lots of mortar, or minimal when efforts are made to eliminate as much reclaimed mortar as possible.

Reclaimed concrete aggregate is mostly angular and varies in mortar content, which will affect how it performs in its ultimate application.

It’s a matter of deciding what your goals are in terms of reclamation, and what the final use of the material will be, and test, test, test and characterize the material accordingly,” Snyder said.

Natural “virgin” aggregates and mortar (cement paste, sand, air and admixtures) comprise RCA. The crushing process results in aggregate particles that are often more angular and rough than typical virgin aggregates, and their properties are somewhat different. RCA typically has a higher absorption capacity, lower speci­fic gravity, greater mass loss in tests such as L.A. abrasion and sodium and magnesium sulfate, and higher chloride content than virgin aggregates, reports ACPA.

Nonetheless, ACPA says, RCA aggregates typically must (and generally do) meet the same requirements as virgin aggregates for the target application, even if the RCA is produced from a concrete pavement with a materials-related distress such as D-cracking or alkali-silica reactivity (ASR). Other concerns with RCA are precipitate potential in the presence of water, and surface dust and contaminants, which can be addressed during RCA production and pavement design.

RCA’s angularity is considered a plus when it’s used as a base course. For example, in the 2007 report, Evaluation of Recycled Portland Cement Concrete Pavements for Base Course and Gravel Cushion Material, done for the South Dakota DOT and FHWA, the researchers concluded “Strong and stable gravel cushion and aggregate base course layers can be attributed to the gradation, angularity and cleanliness of the RCA materials.”

Recycled portland cement concrete pavements have a relatively high level of water absorption, they warned, adding that relatively high level of water absorption could potentially make the proper compaction of gravel cushion and aggregate base course layers variable.

Nonetheless, South Dakota found that “recycled portland cement concrete pavements are a viable option for use in gravel cushion and aggregate base course construction.”

Acceptance of RCA

The last formal survey of RCA use among the states was released in 2004 by the Federal Highway Administration. Its purpose was to capture for technology transfer the most advanced uses of recycled concrete aggregate for use by state highway agencies.

Transportation Applications Of Recycled Concrete Aggregate: FHWA State of the Practice National Review found that concrete routinely is being recycled into the highways of the United States, and its principal application has been as base material.

State transportation agencies were surveyed to determine the current uses of RCA. Forty-one of 50 state DOTs allowed some use of RCA in their specifications, the survey reported. From the results of this survey, five states were identified as being among the highest consumers of RCA in the United States, as well as having large supplies. Their applications were spotlighted in the report, which may be easily located online by “Googling” the title.

“Of those 41 states, 38 were permitting its use in foundation layers, among other applications,” Snyder said. “Foundation layers were the most common application. But its use in pavements is increasing as aggregates costs go up, and haul distances to virgin aggregates become greater. The amount of RCA used is increasing and it’s already fairly high.”

Addressing the need for better guidance, ACPA has articulated guide specifications for use of RCA in road projects, and the American Association of State Highway & Transportation Officials (AASHTO) has a standard specification for use of RCA in foundation layers, and a draft temporary spec for its use in concrete mixes, Snyder said.

The ACPA guide spec is contained in a new publication released in October 2009, Recycling Concrete Pavements. The 102-page technical resource describes concrete pavement recycling as a proven technology that offers an alternative aggregate resource that is both economical and sustainable.

The publication begins with an executive summary and an introduction, and then continues with chapters covering production, properties and characteristics, uses of RCA, and properties, performance, and recommendations for concrete pavement structures containing RCA. Appendices follow, including guidelines for removing and crushing existing concrete; using RCA in unstabilized (granular) subbases: and using RCA in concrete pavement mixtures. Additional appendices include AASHTO and ASTM standards, as well as a glossary of terms.

 The mortar content key

Millions of tons of existing concrete pavement were recycled on the spot in last year’s reconstruction of I-294, the TriState Tollway in suburban Chicago.

The mortar content of the final RCA product is key to a successful application. “Crushed concrete will come down to either large-size coarse aggregate particles, or the ‘glue’ that holds them together, the mortar, which is the cement paste plus sand particles and fly ash or any other admixture,” Snyder told Better Roads.

How much mortar should come off the RCA depends on the ultimate use of the RCA, Snyder said. “It really depends on the application,” he said. “RCA needs to be treated as an engineered material. If you want to maximize reclamation efficiency, so you are reclaiming as much mortar as possible to be as ‘green’ as possible, there are certain types of crushing processes that will remove less mortar. Then you will need to take the presence of that added mortar into account in designing the application.”

RCA from existing pavement was placed as base of reconstructed I-294 in suburban Chicago in 2009.

For example, concrete mix designs may need to be modified to compensate for the higher absorption capacity of the RCA, and base course gradations need to be selected with consideration of the higher abrasion or degradation properties of the material.

“If you are considering the use of high mortar-content RCA in an unbound foundation layer, there may be more potential for leaching of calcium hydroxide, which is a byproduct of the hydration of cement,” Snyder said. “This will result in a high-pH runoff at first, and perhaps the collection of calcium carbonate precipitate in your drain pipes or filter fabric. So you will want to reduce RCA mortar content for this application, use a daylighted base instead of pipe drains, or use the material in an undrained layer instead.”

RCA is not confined to base applications; busy I-10 was completely reconstructed in 1995 as a continuously reinforced concrete pavement containing RCA, and is performing superbly after 15 years.

If the goal is to reclaim as much mortar as possible, and the high mortar-content RCA is going into a concrete mix, it will result in high absorption and lower specific gravity for the aggregate, Snyder said. “Perhaps there will be higher shrinkage as well,” he said. “Thus you may need to shorten up your joint spacing, adjust water content, or use additional fly ash or water reducers to adjust the mix design. You need to test and understand the properties of the RCA so that you can adjust your designs to achieve the performance you want.”

The other end of the spectrum is reclaiming less material while producing an RCA that is as close to natural aggregate as possible. “For that you may use an impact crusher, making an effort to remove as much mortar as possible,” Snyder said. “The mortar can be recycled separately into an undrained base layer, or stabilization layer. The processed RCA with minimal mortar can be placed into a new mix application, without too many mix design adjustments in that case, as you are essentially reusing existing aggregate.”

The production processes might be dictated by the engineer who decides how the material will be used, Snyder said. If the contractor wants to pick the material up and reuse it in the same pavement structure, the selected use of the RCA within that pavement structure will dictate the required handling, crushing and any post-crushing treatments (like washing or air-blowing or other beneficiation) of the material.

Dealing with ASR Concrete

Alkali-silica reactivity, called ASR, is the bane of concrete. Formerly thought to afflict only concrete made with western aggregates, it’s now thought that the potential for ASR-prone aggregates exist in every state.

ASR is a chemical reaction that occurs between alkalis contributed primarily by cement, and a reactive form of silica from reactive aggregate, which forms an alkali/silica gel. Under the right conditions – particularly enough available moisture – the gel will expand and produce stresses and damage in the concrete.

Over time, this expanding ASR gel exerts tremendous internal pressure that can lead to cracking of the concrete. This cracking can provide pathways for potentially deleterious materials such as water, sulfates and chlorides to the interior of the concrete matrix, which in turn can lead to serious durability issues such as freeze/thaw damage, sulfate attack or steel corrosion.

It’s acknowledged that ASR doesn’t destroy concrete per se. Rather, ASR-compromised concrete is weakened so that day-in, day-out wear-and-tear becomes prematurely destructive. Clues to ASR’s destructive chemical reactions include map and longitudinal cracking in bridge decks and pavements, and longitudinal cracking in structural columns.

The best way to avoid ASR in new concrete is to take precautions in the mix design. These include testing aggregates for reactivity, consideration of the use of low-alkali cements, use of suitable pozzolans like ASTM C-618 Class F fly ash, use of lithium-based admixtures, and a basic knowledge of the historical performance of all the materials used.

If ASR-afflicted recycled concrete aggregate is reused in a structure, does the potential exists for ASR damage in the new concrete?

Maybe, maybe not. “There are a number of projects, particularly in Wyoming, where they’ve done large amounts of recycling of badly ASR-distressed pavements, and they’ve done it successfully, with pavements over 20 years old with no ASR,” Snyder said. “But they tested and determined the right combination of fly ash, how much RCA they could use, and how much low-alkali cement was needed to get a good outcome. It worked just fine.”

The Wyoming engineers decided to crush the concrete, lose a lot of the mortar, and limit the amount of reclaimed aggregate that could be used. Class F fly ash was specified as it’s a known mitigator of ASR.

Drain to Fight D-Cracking

D-cracking is another material-related distress in concrete pavements. It’s a concrete deterioration caused by excessive expansion of certain critically saturated coarse aggregate particles during freezing temperatures.

“Many states fight potential recurrent D-cracking by crushing the RCA down to a minus 3/4-in. top size,” Snyder said. “They may also choose to design the pavement with drains or other features that keep the pavement relatively dry. Minnesota has had tremendous success doing this. They had a number of pavements that were badly D-cracked, including one on U.S. 59 that was crushed down to a 3/4-in. top size for the concrete paving mixture, and where the pavement structure included a drained foundation so the pavement would not become critically saturated. That pavement has now been in place for nearly 30 years with no evidence of recurrent D-cracking.”

The solution is to treat RCA as an engineered material. “Again, to use RCA successfully,” Snyder said, “it’s a combination of understanding what you’ve got, understanding the mechanisms involved, and designing so that those undesired mechanisms don’t take place, either chemically in the case of ASR, or mechanically via freeze-thaw in the case of D-cracking.”

On U.S. 52 in Minnesota, cores show concrete pavement containing RCA with angular aggregates, some coated with mortar (left), and virgin aggregate control section (right).

Transverse cracking is a not uncommon problem with pavements containing RCA, but it’s not confined to RCA pavements.

In the 2009 presentation at the Transportation Research Board meeting, Performance of Rigid Pavements Containing Recycled Concrete Aggregates, 2006 Update, by Snyder, David L. Gress, Ph. D., P.E., Recycled Materials Resource Center at the University of New Hampshire, and Jeffrey R. Sturtevant, traffic engineer, Whitney Bailey Cox & Magnani, the authors describe excessive transverse cracking in pavements built prior to 1988 and containing RCA, such as I-94 near Brandon, Minn., where the recycled section developed more deteriorated transverse cracks than did the control section (31 percent vs. 0 percent).

“The transverse cracking was not necessarily related to the use of RCA,” Snyder said. “The jointed reinforced concrete pavement [JRCP] had longer 27-ft. panels, so they were longer than usual and one would expect them to crack anyway. However, the use of RCA in these long panels may have contributed to the deterioration of those cracks because of the higher shrinkage potential and thermal responses of the RCA concrete mixtures. Where RCA was used in jointed plain concrete pavements, we generally did not find excessive cracking in the RCA pavements we revisited.”

Typically, an owner will see a higher coefficient of thermal expansion with RCA, because less natural aggregate is present, and more mortar. “Natural aggregate is a stabilizing influence,” Snyder said. “Mortar has a much higher volumetric expansion and contraction, due to moisture shrinkage or thermal properties. When you increase your mortar content by including both new and reclaimed mortar, you tend to get a little more shrinkage and thermal responsiveness in the pavement. And when you have a long-panel jointed pavement like I-94, your curling and warping stresses will go up as well. In hindsight, some of the problems found on I-94 and other pavements could have been avoided by using shorter joint spacings and/or higher amounts of reinforcing.”

RCA and CRCP

Much of this is moot anyway, as JRCP designs are rarely seen these days, having been replaced by continuous reinforced concrete pavements (CRCP, see Road Science: The ABCs of Continuously Reinforced Concrete, Better Roads, May 2007).

“No one builds much JRCP anymore,” Snyder said. “It’s either continuously reinforced, or short-jointed plain with no reinforcing steel, mostly 15-ft. panels.”

Texas has done major work in the field in evaluating the use of RCA with CRCP, and is confident that it works, thanks to the largest application to-date of RCA in CRCP in 1995, a very heavily traveled section of I-10 in Houston between Loop 610 and I-45 involving 10 lanes, including HOV lanes.

Reconstruction of Houston’s I-10 (from Loop 610 to I-45) was the first project in the state in which all recycled aggregate was used for pavement concrete, according to TxDOT. Today, crushed concrete is used extensively in state projects in the Houston area and is fairly common in Dallas as well.

“Concrete from existing roadways, pavements, airfields, and buildings can be reused,” said Dr. Moon Won, P.E., now with Texas Tech University, who oversaw the I-10 work when with TxDOT.

“The project recycled everything, with nothing but recycled concrete aggregate, both coarse and fine, into the surface layer, and coarse and fine aggregates in the base layer,” Snyder said. “It was a huge project, now in place 15 years, and it looks great.”

The DOT’s objectives of the I-10 study were to evaluate the engineering properties of RCA and portland cement concrete made with RCA, investigate the effect of RCA and PCC properties on CRCP performance, and develop guidelines for the effective use of RCA for CRCP.

There are a number of factors affecting CRCP performance with RCA, TxDOT said. They include adequacy of the pavement structure, material properties, environmental conditions during concrete placement, and construction practices. The study included laboratory evaluation of RCA and PCC material properties, performance evaluation of CRCP with RCA sections in the Houston District, and analysis of information to develop guidelines for the use of RCA in CRCP.

TxDOT found that the CRCP sections utilizing 100-percent recycled coarse and fine aggregates have performed well. No distresses, including spalling, wide cracks, punchouts, or meandering cracks, have taken place. Transverse crack spacing distributions are comparable to those in concrete with natural siliceous river gravel.

The large amount of old mortar in recycled coarse aggregate did not appear to have an adverse effect on CRCP performance, TxDOT said. Moisture control of recycled aggregate was critical in producing consistent and workable concrete. No significant adjustment in paving operations was necessary due to the use of 100 percent recycled coarse and fine aggregate in concrete.

The agency found that RCA in this project did not have a pronounced effect on compressive strength, but that recycled fine aggregates had an adverse effect on flexural strength. The use of both recycled coarse and fine aggregates reduces modulus elasticity significantly, TxDOT said. For the same water/cement ratio, replacing virgin sand with recycled sand did not result in changes in tensile strength.

Echoing Snyder, the state reported that the thermal coefficient of concrete containing 100 percent recycled aggregate is much higher than that of virgin aggregate concrete, and that recycled coarse aggregate has a much higher thermal coefficient than virgin aggregate due to the attached old mortar.

Constructing the I-10 segment was not without complications, TxDOT said. In the beginning of the project, there was a problem producing concrete with consistent workability that met the minimum strength requirement. “The primary reason for inconsistent workability was due to the lack of moisture control of recycled aggregate,” TxDOT said “A better sprinkler system was installed later for aggregate stockpiles, and moisture of the recycled aggregate was better controlled. This system mitigated the inconsistent workability problem.”

Paving operations were closely monitored to identify any variations that might result from using the recycled aggregate. Not much difference was observed.

RCA and TriState Tollway

More recently, in 2009, RCA from the existing pavement was used in the complete reconstruction and widening of the TriState Tollway (I-294) in suburban Chicago, from the Wisconsin to the Indiana border.

The Illinois State Toll Highway Authority (ISTHA) said all existing concrete pavement was crushed on site and reused as base stone under new roadways.

“Recycling the existing road materials not only saved the cost of purchasing new materials for the roadway beds, but also eliminated the cost of hauling the old materials from the work site and disposal in landfills,” the authority said.

It resulted in 3.2 million tons of concrete recycled, which is enough concrete to build 4,000 miles of sidewalk, which would equal the distance from Chicago to San Diego and back, ISTHA said.

On the project, excavated concrete was broken up and crushed into smaller pieces – right on the roadway construction site with the use of mobile crushers – to create a high-quality aggregate base for new pavement. Up to 90 percent of each new roadway base consisted of recycled concrete.

But “Bein’ Green” means that you need to get recognition of it as well. Thus beginning in October 2009, roadway signs were being installed along the newly reconstructed roadways throughout the 286-mile tollway system to inform drivers that improvements have been made using “green” construction methods and materials.

“We will see much more of this in urban areas,” Snyder told Better Roads. “The hauling required to remove demolition concrete, and return with virgin aggregate, constitutes an unnecessary added cost. What the Illinois State Toll Highway Authority did was a model for the way highway agencies ought to be doing this in the future.”

RCA in Patch Mixes

RCA is going into ready-mixed patch materials, too, being part of the 50-percent recycled material content of Quickcrete Green Concrete Mix. The material’s recycled content also includes fly ash or slag cements, or both, the company reports.

Green Concrete Mix diverts material from the waste stream and preserves virgin aggregate resources. As an example, for each 60-lb. bag of the material, there is 0.25 cubic feet of waste diverted from the landfill volume. After an initial launch of the product in the Seattle, Portland, Ore., and northern California markets, Green Concrete Mix is now available in the Denver, Columbus, Salt Lake City and New England markets.v

Recycled Concrete Aggregate Best Used as an Engineered Material

The grants, from the Federal Highway Administration’s “On the Job Training/Supportive Services” program, will fund pre-apprenticeships and training centers in California for women, minorities, veterans, and disadvantaged individuals pursuing careers in the highway construction industry.

“These grants will help to create opportunities during these tough economic times. We are providing crucial job training to people that will help lay the groundwork for jobs and drive California on the road to economic recovery,” said Governor Arnold Schwarzenegger in a written statement.

California’s grant recipients are the following:

• The California Disabled Veteran  Business Alliance in Sacramento received $367,483 to provide education and training for veterans seeking skilled highway construction jobs.
• The Center for Training and Careers in the cities and counties of San Jose, Alameda County, Fresno County, Los Angeles County and San Joaquin County participating in the “Foundation Builders-Working Together to Build a Better Foundation” program received a total of $796,415. These funds will provide outreach, recruitment, orientation, work readiness training, supportive services and placement assistance.
• The Century Community Training Program in Los Angeles received $290,000, which will provide construction industry skills training in highway, street and bridge construction, placement, and supportive services to increase participation by women, minorities and disadvantaged individuals in highway construction.
• The Family Management Matters ”Warriors Career Bridge” program in Anaheim and Orange County received $256,620. These funds will establish communication channels between veteran organizations and public works employers to identify the veteran’s skill gaps. These funds will also work toward implementing an internship/training program to prepare veterans for careers in public works and transportation infrastructure development and maintenance.
• The Northern California Teamsters Apprentice Training and Education Trust Fund in Rancho Murieta received $208,543 to provide participants with a five-week commercial driver license course, plus an additional two weeks of specific construction vehicle training.
• The Pacific Gateway in Long Beach received $230,789 to provide outreach and recruitment, orientation, assessment, construction-related training, on-the-job training, intensive placement activities, supportive services, job referral, job placement, and job retention assistance in high paying, skilled highway construction positions.
• The Sacramento Employment and Training Agency received $338,590 to provide women, minorities and other disadvantaged individuals construction industry skills training and support to increase their participation in highway construction.
• The United Job Creation Council Re-entry Construction Employment Project in Los Angeles received $254,840, which will be used to gain access to job preparation, training, and retention opportunities by providing highway construction industry skills training, tools and equipment.

“These grants will provide people the required skills to find jobs in highway construction and create a trained workforce to improve our transportation infrastructure for generations to come,” said Caltrans Director Randy Iwasaki in a Caltrans press release.

Under Governor Schwarzenegger’s leadership, California leads the nation with $2.54 billion in Recovery Act funding obligated to 912 highway, local street, and job training transportation projects statewide. For more information on the Recovery Act, to go http://recovery.ca.gov/

The grants, from the Federal Highway Administration’s “On the Job Training/Supportive Services” program, will fund pre-apprenticeships and training centers in California for women, minorities, veterans, and disadvantaged individuals pursuing careers in the highway construction industry.

“These grants will help to create opportunities during these tough economic times. We are providing crucial job training to people that will help lay the groundwork for jobs and drive California on the road to economic recovery,” said Governor Arnold Schwarzenegger in a written statement.

California’s grant recipients are the following:

• The California Disabled Veteran  Business Alliance in Sacramento received $367,483 to provide education and training for veterans seeking skilled highway construction jobs.
• The Center for Training and Careers in the cities and counties of San Jose, Alameda County, Fresno County, Los Angeles County and San Joaquin County participating in the “Foundation Builders-Working Together to Build a Better Foundation” program received a total of $796,415. These funds will provide outreach, recruitment, orientation, work readiness training, supportive services and placement assistance.
• The Century Community Training Program in Los Angeles received $290,000, which will provide construction industry skills training in highway, street and bridge construction, placement, and supportive services to increase participation by women, minorities and disadvantaged individuals in highway construction.
• The Family Management Matters ”Warriors Career Bridge” program in Anaheim and Orange County received $256,620. These funds will establish communication channels between veteran organizations and public works employers to identify the veteran’s skill gaps. These funds will also work toward implementing an internship/training program to prepare veterans for careers in public works and transportation infrastructure development and maintenance.
• The Northern California Teamsters Apprentice Training and Education Trust Fund in Rancho Murieta received $208,543 to provide participants with a five-week commercial driver license course, plus an additional two weeks of specific construction vehicle training.
• The Pacific Gateway in Long Beach received $230,789 to provide outreach and recruitment, orientation, assessment, construction-related training, on-the-job training, intensive placement activities, supportive services, job referral, job placement, and job retention assistance in high paying, skilled highway construction positions.
• The Sacramento Employment and Training Agency received $338,590 to provide women, minorities and other disadvantaged individuals construction industry skills training and support to increase their participation in highway construction.
• The United Job Creation Council Re-entry Construction Employment Project in Los Angeles received $254,840, which will be used to gain access to job preparation, training, and retention opportunities by providing highway construction industry skills training, tools and equipment.

“These grants will provide people the required skills to find jobs in highway construction and create a trained workforce to improve our transportation infrastructure for generations to come,” said Caltrans Director Randy Iwasaki in a Caltrans press release.

Under Governor Schwarzenegger’s leadership, California leads the nation with $2.54 billion in Recovery Act funding obligated to 912 highway, local street, and job training transportation projects statewide. For more information on the Recovery Act, to go http://recovery.ca.gov/

“The U.S. Department of Transportation has an excellent history of reaching out to small businesses owned by women, veterans and minorities,” said LaHood in a press release. “Nearly half the contracts we award each year go to these types of firms.”

The “Disadvantaged Business Enterprise/Supportive Service (DBE/SS)” grants are part of an ongoing federal effort to help state departments of transportation train certified DBE firms on subjects ranging from contract and business management, to procurement assistance and how to secure bonding. The goal of the program is to help them successfully compete for federal highway projects.

“By helping small businesses like DBEs, this program enriches the competition for federal highway contracts,” said Federal Highway Administrator Victor Mendez in a written statement. “More vigorous competition not only results in lower costs to taxpayers for roads and bridges, but more jobs for workers.”

A DBE is a for-profit, small business owned by minorities, women or economically disadvantaged individuals or, in the case of a corporation, in which 51 percent of the stock is owned by one or more such individuals. The daily business operations must be controlled by at least one of the socially and economically disadvantaged owners.

In 1982, FHWA began promoting the participation of DBEs in federal-aid highway contracts through the development of state-run supportive services programs. “Supportive services” are those activities that are designed to contribute to the growth and eventual self-sufficiency of DBEs so they may improve their ability to compete for federal highway contracts and subcontracts.

For more information about FHWA’s DBE program, go to http://www.fhwa.dot.gov/civilrights/dbe_program_i.htm.

The 2010 DBE/SS award recipients include the following:

State Allocation Amount

Thanks to the American Recovery & Reinvestment Act’s enactment one year ago today, hundreds of thousands of jobs in the transportation construction industry have been supported by the measure’s investments in critical infrastructure upgrades.  In fact, given state budget difficulties and significant declines in private sector transportation construction activity, the recovery act was one of the few bright spots for our industry in 2009.

To appreciate the success of the recovery act’s transportation provisions, it is necessary to sidestep the political rhetoric about “outlays” and jobs created vs. saved.  The simple facts from the Federal Highway Administration (FHWA) and Federal Transit Administration (FTA) are that as of February 17:  

• $16.84 billion in recovery act highway funds are under construction;
• $8.46 billion in highway funds have been committed for specific projects;
• $7.24 billion in recovery act public transportation funds have been awarded; and
• $1.07 billion in public transportation funds are pending award.

As such, almost 63 percent of the act’s highway funds and 86 percent of the public transportation funds are currently generating economic activity and supporting employment.  Once the pending funds are awarded, both categories of funding will have deployed nearly 100 percent of their resources to support critical transportation improvements that boost the U.S. economy.      

That this work is underway and ahead of the forecast schedule is undeniable.  It is equally obvious that American workers are being employed to build these projects.  Therefore, the only logical conclusion is that the recovery act’s transportation investments are fulfilling their intended goal.

While the success of the transportation recovery funds is a clear success story, failure to promptly continue progress in addressing the U.S. infrastructure deficit jeopardizes these gains.  These resources were never intended to substitute for the long-term transportation solution our economy requires.  Passing a multi-year reauthorization bill with robust highway and public transportation investment is one of the best steps Congress can take to provide lasting economic benefits and contribute to long-term job creation.  

Pending congressional action on a multi-month extension that stabilizes the Highway Trust Fund would provide Congress and the Obama Administration the time necessary to develop a critical multi-year surface transportation reauthorization bill.

State departments of transportation are required by ARRA guidelines to obligate (or commit funds to a specific project) all their economic stimulus funds by March 2 or risk losing those uncommitted.

“From launching the nation’s first transportation stimulus project to obligating all of our recovery act funds ahead of schedule, MoDOT has worked rapidly to show that transportation projects do play an integral role in supporting jobs and rebuilding our nation’s economy,” said MoDOT Director Pete Rahn in a written statement. “While these funds don’t come close to covering all of our transportation needs, they have helped fill a short-term gap as other federal and state resources continue to decline.”

To date, the Missouri Highways and Transportation Commission has awarded 187 economic stimulus projects totaling $469 million. The ARRA funding awarded to date will support 12,524 direct, indirect and induced jobs based on Federal Highway Administration estimates.

Pushing to obligate this funding as quickly as possible in a competitive bidding environment resulted in overall bids coming in $24 million under what MoDOT had estimated. That savings enabled the department to add another 53 recovery act projects.

MoDOT got a jumpstart on meeting the deadline by being the first state in the nation to have a recovery project under way within minutes of President Barack Obama signing the act.

More information on Missouri’s recovery act projects can be found at www.modot.org/readytogo.