By Greg Sitek
Did you ever wonder where we’d be without roads? Without roads we certainly would not be the United States; the east coast would never have met the west coast; the north would never have met the south; railroads would never have been built across the country; the telegraph and telephone would never have spread their spider-like lines of communication; electricity would lack a system of distribution; newspapers would sit on docks; cars and trucks would have no purpose; we’d have no way of getting to airports or out to dinner or to go shopping; we wouldn’t be able to go to work; and of course without all this there could be no Internet. This litany barely starts the list of what roads mean to us, our commerce, our civilization and our society.
We need our roads.
In our comparative brief history in international commerce it has been our transportation infrastructure that has catapulted us to world leadership.
To be a player, let alone the dominant player, in global commerce, we need the best transportation infrastructure on planet earth. We have the wherewithal to update and improve what we already have and maintain that leadership role.
Asphalt is one of the key ingredients in doing this.
There are concerns about our environment, global warming, oil and a host of other things. Asphalt and the people who produce asphaltic pavements have been addressing these concerns since the late 1970s when the industry fought and won a battle to use
recycled asphalt pavements. Going back to that time, it seems strange that there were people in the government, industry, society and academia who were against the concept. As a result of the efforts of recycling pioneers, the concept was accepted and became an integral part of asphalt paving, making it a leader in “green” construction.
According to National Center for Asphalt Technology (NCAT), 96 percent of all paved roads and streets in the U.S. – almost 2 million miles – are surfaced with asphalt. The Hot Mix Asphalt (HMA) industry directly employs approximately 300,000 people, and indirectly accounts for an additional 600,000 jobs. On an average, the industry produces and places approximately 500 million tons of hot mix asphalt annually valued at some $20 billion. When combined with state and federal employees associated with the construction and maintenance of asphalt-surfaced roads, the HMA industry has a significant impact on the economic vitality of the nation. NCAT was established to ensure the HMA industry meets this challenge and improves pavements.
NCAT ensures this industry’s ability to provide pavements that are durable, environmentally friendly, quiet, safe and economical. NCAT works with state highway agencies, the Federal Highway Administration and the highway construction industry to develop and evaluate new products as well as design technologies and construction methods, which quickly lead to pavement improvements. Its research center and test track make it one of the world’s leading institutions for asphalt pavement research and an important source of information for those tasked with maintaining our nation’s infrastructure.
NCAT started operating in 1986 through an agreement between the National Asphalt Pavement Association (NAPA) Research and Education Foundation and Auburn University. The visionary leadership of dozens of individuals, in conjunction with companies associated with the Hot Mix Asphalt (HMA) industry, large and small, brought about this joint venture at a truly appropriate time.
The asphalt industry owes much of its development to a number of associations that are dedicated to providing the country with the most economical highway system in the world. As with most such organizations, these groups are comprised of the individuals working in the industry. Understanding who they are and what they do provides a deeper insight into the industry and its future.
The National Asphalt Pavement Association (NAPA) represents the interests of the Hot Mix Asphalt producer and paving contractor on the national level with Congress, government agencies, and other national trade and business organizations. NAPA supports an active research program designed to answer questions about environmental issues and to improve the quality of HMA pavements and paving techniques used in the construction of roads, streets, highways, parking lots, airports, and environmental and recreational facilities. The Association provides technical, educational, and marketing materials and information to its members, and supplies technical information to users and specifiers of paving materials. The Association, which counts more than 1,100 companies as its members, was founded in 1955. There is more to come from NAPA later in this article.
The Asphalt Recycling & Reclaiming Association (ARRA) was founded to help the industry standardize methods, equipment, nomenclature, standards and training for the recycling end of the business. In ARRA’s outlook statements, the association states:
“No matter what goes on with politics, social issues, anti-terrorism policies and procedures, or the economy, one thing is certain – America needs its highways. Everyone acknowledges that sooner or later all roads have to be maintained, preserved, and rehabilitated, and that the methods represented by ARRA offer the least expensive, longest lasting alternatives for stretching available dollars. Our future is bright!
“ARRA members are an integral part of this continuing effort for system preservation and rehabilitation to provide a safe, cost-efficient, and comprehensive network of roads and highways. The asphalt recycling and reclaiming industry remains a strong, healthy component of the highway maintenance, rehabilitation, and preservation market. Public agencies are stretching their dollars by paying increased attention to the benefits of recycling, and reclaiming their existing asphalt pavements. Environmentalists, taxpayers and legislators will be pleased to know that ARRA member contractors are responsible for keeping literally millions of tons of asphalt out of North American landfills.
“ARRA continues to take steps to increase its visibility on federal, state, and local levels. We are actively involved with the FHWA, FP2 (Foundation for Pavement Preservation), and the new National Center for Pavement Preservation. Our 2006 Annual Meeting was again held jointly with Asphalt Emulsion Manufacturers Association (AEMA) and International Slurry Surfacing Association (ISSA). ARRA officials in the past year have come to Washington, D.C. to meet with key Federal Highway Administration officials and highway industry association executives. ARRA’s membership in the American Highway Users Association, the Transportation Construction Coalition, and TRIP (The Road Information Program) – three of the main forces behind the passage of SAFETEA-LU, and institutional leaders in making sure that SAFETEA-LU funds are spent on the highways – helps keep us attuned to what is going on at the Federal level and provides us with key contacts. A cornerstone of ARRA’s efforts to increase the market share for recycled asphalt has been our work through local organizations, universities, and technology transfer centers to conduct seminars which benefit those involved in the design, construction and maintenance of streets, roads and highways.”
The Road Information Program, TRIP, a national research group, was founded in 1971. TRIP is a nonprofit organization that promotes transportation policies that relieve traffic congestion, improve road and bridge conditions, improve air quality, make highway travel safer and enhance economic productivity.
Under the leadership of its executive director, Will Wilkins, The TRIP staff provides an invaluable service to the industry and the country. TRIP reports focus on transportation infrastructure conditions. Individual state or city reports are developed at the request of the respective state or city. TRIP researchers and analysts collect information and develop reports on the state of the
requestor’s city or state. Typically these reports are made public and aired over radio and TV network stations. In the last three or four years, Trip has developed over 50 state/city reports and 10 national reports. If you are interested in information on our transportation infrastructure, visit the TRIP website at www.tripnet.org.
American Society of Civil Engineers (ASCE) was founded in 1852, represents more than 147,000 members of the civil engineering profession worldwide, and is America’s oldest national engineering society. ASCE’s vision is to position engineers as global leaders building a better quality of life. Early in 2009, to provide guidance for the application of stimulus fund allocation, ASCE published its Report Card for America’s Infrastructure. This report was widely publicized in the national media, online and in industry trade journals.
Look at the condition of the components of our transportation infrastructure, as reported on one year ago. A quick look shows that our overall transportation infrastructure is in very poor shape:
Inland Waterways D-
With respect to our roads, ASCE’s report states:
“Americans spend 4.2 billion hours a year stuck in traffic at a cost of $78.2 billion a year–$710 per motorist. Roadway conditions are a significant factor in about one-third of traffic fatalities. Poor road conditions cost U.S. motorists $67 billion a year in repairs and operating costs–$333 per motorist; 33% of America’s major roads are in poor or mediocre condition and 36% of the nation’s major urban highways are congested. The current spending level of $70.3 billion for highway capital improvements is well below the estimated $186 billion needed annually to substantially improve the nation’s highways.”
And as for our bridges, ASCE’s report states:
“More than 26%, or one in four, of the nation’s bridges are either structurally deficient or functionally obsolete. While some progress has been made in recent years to reduce the number of deficient and obsolete bridges in rural areas, the number in urban areas is rising. A $17 billion annual investment is needed to substantially improve current bridge conditions. Currently, only $10.5 billion is spent annually on the construction and maintenance of bridges.”
What will it take to fix the problem?
The National Surface Transportation Policy and Revenue Commission studied the impact of varying investment levels (medium and high) and produced the following ranges of average annual capital investment needs (in 2006 dollars):
- $130 billion-$240 billion for the 15-year period 2005-2020;
- $133 billion-$250 billion for the 30-year period 2005-2035;
- $146 billion-$276 billion for the 50-year period 2005-2055.
The lower-end ranges reflect the estimated costs of maintaining key conditions and performance measures at current levels (the status quo), while the higher-end ranges would allow for an aggressive expansion of the highway system, which would provide improved conditions and performance in light of increasing travel demand. Even at the lower range of estimates, an enormous gap exists between the current level of capital investment and the investment needed to improve the nation’s highways and roads.
There are numerous other associations that are deeply involved in many varied aspects of our transportation infrastructure. Associated General Contractors of America (AGC), American Road and Transportation Builders Association (ARTBA), American Association of State of Highway Transportation Officials (ASHTO and/or AASHTO), American Concrete Pavement Association (ACPA), Association of Equipment Manufacturers (AEM), Associated Equipment Distributors (AED), Portland Cement Association (PCA) and literally dozens of others are concerned about our transportation infrastructure.
The bottom line is that our transportation infrastructure is in need of a serious overhaul that cannot be delayed much longer. The
rate of deterioration will only accelerate with the passage of time. If we don’t address the problem, bad roads will worsen, congestion will intensify, and bridges will become unsafe. Asphalt paving is an important ingredient in our formula for rebuilding our roads and our economic strength. It is also a critical component in addressing climate change and other environmental issues.
On March 31, 2009, Mike Acott, president of NAPA, addressed the subcommittee on Technology and Innovation on the Role of Research in Addressing Climate Change in Transportation Infrastructure. He responded to two questions.
1. Is research needed to help address climate change and other environmental issues in transportation infrastructure? What purpose would it serve?
2. What issues and topics should be encompassed within a research agenda to address climate change and other environmental issues in transportation infrastructure? How should the research agenda be implemented?
Acott started his testimony with a statement regarding the reauthorization of the highway bill which, as we know, has been temporarily extended, now for the second time. “In the next five years,” he stated, “we can achieve significant gains in addressing climate change by accelerating research and deployment of technologies that reduce greenhouse gas emissions. These include warm-mix asphalt, reuse/recycling and Perpetual Pavements. Also worthy of attention are porous asphalt pavement technologies.
“By 2014,” he continued, “with assistance in applied research and technology deployment that may be provided through the next highway bill, we can increase use of warm-mix asphalt to represent the majority of all the pavement material produced in the U.S.; we can double the reuse/recycling of asphalt pavements; make Perpetual Pavements the standard design method; and have porous pavements accepted as a best management practice for reducing stormwater runoff and improving water quality.”
Each of the technologies Acott noted exists but can be improved through additional research and technological development. This is where NCAT becomes an important partner in the future of asphalt pavements.
“We believe there is a critically important role for the federal government in helping to fund the development and evaluation of these new technologies, assess their long-term performance, and ensure their deployment. A primary focus should be to get greenhouse gas-reducing technologies onto the roads in all the states.”
The new federal highway bill, once passed, should specify funding that would foster and aid this type of research. It will make a difference in how are roads are built and how long they last.
The four technologies that Acott referenced are: (1) warm-mix asphalt, (2) reuse/recycling, (3) Perpetual Pavements and (4) porous asphalt. Lets take a look at what Acott had to say about them and how they fit into the future of highway pavements.
(1) Warm-Mix Asphalt
Warm-mix technologies allow production and placement of asphalt pavement material at lower temperatures than conventional technologies. Conventional asphalt pavement material is produced at around 320 degrees Fahrenheit, and warm mix is typically produced at temperatures ranging from 280 degrees F down to 212 degrees F. Since the first public demonstration of warm mix in the U.S. in 2004, warm mix projects have been constructed in all but 10 states.
Warm mix was originally explored for its environmental benefits, which include reduced fossil fuel consumption and reduced emissions, including greenhouse gas emissions. Contractors and agencies have also discovered numerous construction benefits, including the potential to extend the paving season in northern climates, the potential to store pavement mix for longer periods, a longer window of opportunity for compacting pavement, and increases in recycling rates.
Running warm mix can reduce energy consumption during the manufacturing of the asphalt pavement mixture by an average of 20 percent, which decreases total life-cycle greenhouse gas emissions by 5 percent. This equates to 1 million tons offset annually. Combining warm mix with reuse/recycling yields even greater benefits. Warm mix with 25 percent reclaimed asphalt pavement could potentially offset asphalt pavement life-cycle greenhouse gas emissions by 15 to 20 percent. The potential for total savings in greenhouse gas emissions using both warm mix and recycling is about 3 million tons per year.
NAPA, FHWA, AASHTO and researchers created a Technical Working Group whose purpose is to evaluate warm-mix technology performance, quantify environmental benefits, develop performance specifications, provide technical guidance and disseminate information. The partnering approach has provided immense support to efforts to deploy warm mix.
So far, implementation has proceeded with virtually no complications. Demonstration projects, trials and test projects have included the full variety of asphalt mixture types. At least 10 states have adopted permissive specifications, clearing the way for contractors to produce and place the mix at low temperature as long as it meets all other criteria.
Experience with applied research and technology development suggests that warm mix may make it possible to increase the rates of reuse/recycling even further. Applied research on this topic could be helpful in speeding the rate of acceptance of combining the two technologies.
Another opportunity for applied research is full documentation of emission reductions, with specific focus on greenhouse gas emissions. Such research would assist other agencies in taking full advantage of warm mix to meet air-quality guidelines. Research funding will be needed both for emissions studies and for monitoring of long-term pavement performance.
(2) Doubling the Use of Reclaimed Materials in Asphalt Pavements
The use of reclaimed asphalt pavement (RAP) has been widespread for about 30 years. Asphalt pavement is America’s most recycled material. Every year, more than 100 million tons of asphalt pavement material is reclaimed and virtually all of which are recycled into new pavements. Materials from other industries, including roofing shingles and ground rubber from used tires, can also be beneficially incorporated into asphalt pavements. The key to this is sound engineering, design, and technology.
Consumption of fuels in the process of acquiring and processing raw materials accounts for a significant share of the greenhouse gas emissions associated with producing asphalt pavement material. Therefore, it is possible to reduce greenhouse gas emissions simply by incorporating RAP in new pavement. Currently, the average rate of reuse/recycling is 12 percent. These numbers include both states that routinely use 30 percent RAP and states that permit minimal use. Using 25 percent RAP reduces total life-cycle greenhouse gas emissions by 10 percent, which equates to 2 million tons offset annually.
A singular quality of asphalt cement is that it is rejuvenated when RAP is incorporated into new pavement, becoming an integral part of the binder. This is referred to as the highest and best use.
In view of the high reuse/recycling rate in lead states, including a preponderance of evidence that the quality of asphalt pavements incorporating RAP is equal to or better than pavements using all virgin materials, there is ample opportunity to double the quantity of RAP used within five years.
Part of the challenge is to encourage agencies in rural areas to allow milling on pavements prior to the placement of asphalt overlays. This will provide more material for recycling in areas where RAP is scarce, and it will improve the performance of the rehabilitated pavement by removing distresses from the existing surface.
Reuse/recycling is not only an environmentally sustainable practice, it is an economically sustainable one. NAPA estimates that we have 18 billion tons of asphalt pavements already in place on America’s roads and highways. Because of the ability to reuse and recycle this material indefinitely, our highways are a resource for future generations. Not only are our roads a primary engine of the economy, they have a high residual value as a source of construction materials. As a note, the process of reclaiming and processing these materials has a very low environmental impact.
FHWA has organized the RAP Expert Task Group (ETG), which brings together stakeholders from government, industry, and academia to investigate obstacles to increasing RAP use. As part of this mission, the ETG has identified states with particularly high and particularly low levels of reuse/ recycling. The ETG is also charged with achieving the desired increases through technology transfer/accelerated deployment strategies, and eliminating artificial and arbitrary barriers to increased recycling in favor of performance-based pavement criteria.
There are also opportunities for applied research, including quantifying the environmental benefits of increased RAP use, developing technologies and procedures to recycle high percentages of reclaimed material, developing technologies and procedures to better preserve the aggregate gradation in RAP, and improving performance testing methods and specifications for use of RAP and roofing shingle mixtures. All these activities would contribute to increasing the overall rate of recycling and therefore reductions in emissions of greenhouse gases.
(3) Perpetual Pavement
Perpetual Pavement is the name given to an asphalt pavement that is designed not to fail. Construction is in layers whose properties serve a combination of different functions; they all add up to an extraordinarily long-lasting pavement. Surface distresses may occur eventually, but they do not penetrate deep into the pavement’s structure. Routine maintenance involves infrequent milling of the top layer for recycling, then placing a smooth, quiet, durable and safe new overlay. A Perpetual Pavement never needs to be completely removed and replaced. In the world of pavements, this is the ultimate in economic and environmental sustainability.
Perpetual Pavements can mitigate climate change by reducing greenhouse gas emissions, both now and for generations to come. Perpetual Pavements reduce greenhouse gas production several ways. Since only the surface is renewed, the base structure stays in place, thereby significantly reducing greenhouse gases associated with acquisition and placement of virgin raw materials. Greenhouse gas emissions associated with complete removal and replacement of pavements that have reached the end of their useful life are avoided.
Additionally, greenhouse gas emissions associated with construction delays are greatly reduced because maintenance and rehabilitation can be done quickly in off-peak hours, unlike the remove-and-replace option, which necessitates 24-hour road closures. Limiting closures to off-peak hours can reduce delays for road users by at least a factor of 12.
Perpetual Pavements are more cost-effective than traditional asphalt pavements while enhancing durability, performance and long life. Reuse/recycling is part of the maintenance and rehabilitation process. All these factors conserve construction materials and reduce greenhouse gases.
Once the road is constructed, it becomes a permanent asset within the transportation infrastructure system. A Perpetual Pavement never becomes a reconstruction problem for future generations.
Perpetual Pavements can also keep roads smoother. Significant fuel savings are associated with smooth pavements. It has been documented under tightly controlled conditions that driving a heavily loaded truck on a smooth road consumes about 4.5 percent less diesel than driving on a rough one.
The history of Perpetual Pavements goes back to the 1960s, although the term was not used until around 2000. Full-depth asphalt pavements first achieved wide acceptance in the 1960s as a way of minimizing materials use and construction costs. At that time, it was assumed that the design would result in a “20-year design life,” but experience has shown that such pavements have lasted for over 40 years with no sign of structural failure. Engineering studies in the states of Kansas, Minnesota, Ohio, Oregon and Washington have validated these observations.
Beginning in 1999 and 2000, asphalt pavement researchers initiated efforts to understand the engineering features and performance characteristics of Perpetual Pavements. Research has been conducted at NCAT, the Asphalt Institute, the University of California at Berkeley, the University of Illinois, and other leading institutions in the U.S. and around the world. The research has led to the development of materials, design methods and performance criteria to enable agencies to design pavements that ensure long life without wasting materials due to overdesign.
There are already many pavements around the United States that fit the Perpetual Pavement definition. In recognition of that fact, in 2001 the asphalt industry created a program to identify Perpetual Pavements and honor the agencies that have designed and maintained them. Fifty Perpetual Pavement Awards have been presented since that time.
There are many opportunities to accelerate deployment of Perpetual Pavement technologies. Full integration of Perpetual Pavement into the new AASHTO Mechanistic-Empirical Pavement Design Guide would be very helpful. Open houses, demonstration projects, conferences, publications and webinars can also help to push implementation forward.
There are currently two national studies on Perpetual Pavement through the National Cooperative Highway Research Program (NCHRP) focused on the engineering characteristics that will be critical to the design of long-life pavements. Such pavements have been constructed with instruments embedded in the various layers to ascertain their responses to truck loadings at a variety of locations. These include the NCAT Pavement Test Track and the Minnesota Road Research Project, as well as in highways located in Kansas, Ohio, Pennsylvania, Wisconsin and other states. These will provide crucial information on the field behavior of Perpetual Pavements.
Significant opportunities for applied research on Perpetual Pavements include an investigation of high-stiffness base materials, which have the potential to reduce both costs and greenhouse gas emissions, and research on the impact of these long-life pavements on climate change, specifically greenhouse gases.
In summary, Perpetual Pavements conserve natural resources, reduce life-cycle costs, save fuel, and reduce fuel consumption and greenhouse gas emissions.
(4) Porous and Open-Graded Pavements
Porous and open-graded asphalt pavements have been shown to have a dramatic and beneficial effect on water quality. These pavements have been used widely for over 30 years with an excellent record of success. Open-graded pavement is made with same-size rocks, creating a web of interlocking pores that allow water to flow through the surface.
Open-graded pavements are used mainly in two types of applications:
First, open-graded friction courses are widely used for surfacing roads and highways. The pavement layer directly beneath this is impermeable. During a rainstorm, instead of pooling on the surface or bouncing off it, rain drains through the surface and out to the sides. Splash and spray are greatly reduced, enhancing safety.
Second, porous pavement systems are stormwater-management tools with an open-graded surface over a stone recharge bed. The system is designed and constructed to collect stormwater, which then infiltrates into the ground. Porous pavement systems are used mostly for parking lots, but they have also been used successfully for roads in communities like Pringle Creek in Salem, Ore.
Both applications can be used to improve water quality. Porous asphalt surfaces allow roads and highways to function as linear stormwater-management systems. Porous parking lots store stormwater, reduce runoff, promote infiltration and groundwater recharge, allow evaporative cooling of the atmosphere, diminish erosion on stream banks, reduce particulates in stream water after storms, and improve water quality.
Porous asphalt pavements are accessible and affordable. They can be produced and constructed by any qualified contractor. Open-graded highway surfaces have additional environmental and safety benefits; for example, they reduce road noise significantly. Texas DOT reported that replacing a conventional surface with open-graded friction course in a high-accident area reduced wet-weather accidents by 93 percent and reduced fatalities by 86 percent.
With respect to porous pavement systems for stormwater management, some local authorities may allow the construction of porous pavement systems but still require total redundancy with the use of conventional stormwater-management structures. Applied research documenting the effectiveness of porous pavements, together with a program of continuing education, could be helpful. It is important to recognize, however, that porous pavements are not appropriate for all sites, and therefore legislative or regulatory mandates for porous pavement systems would be counterproductive.
The significant benefits of porous asphalt make it desirable to accelerate their deployment, and there are many opportunities to do so. Applied research, demonstration projects, open houses, Internet-based tools and other continuing education efforts focusing on the use of porous asphalt could result in accelerated deployment.
Implementation could be further assisted through development of design guidance for use by federal government agencies such as the DOT, EPA, U.S. Army Corps of Engineers, Parks Service, Forest Service and National Fisheries Service.
Opportunities for applied research include documenting the environmental effectiveness and cost benefits of porous asphalt pavement, improving materials and mix designs, and evaluating highways as linear stormwater-management systems.
Road to the Future
In addition to these asphalt pavements noted above, let’s not forget about the standard Hot Mix pavements. They have served us well and will continue to do so in the future. If you are a paving contractor, it is in your best interest to learn as much as you can about developing trends. The future for paving is probably better today than it has ever been. No matter what happens with the highway trust fund, we will be rebuilding and improving existing roads as well as adding new roads to the system.
Without our roads there is no way we can move into the future …
NOTE: This article appeared in the February issues of the ACP magazines.