Right choice, right now

Nov. 13, 2008

Oil pricing volatility and sustainability are among the most pressing and critical issues agencies and the pavement industry are facing today.

Oil pricing volatility and sustainability are among the most pressing and critical issues agencies and the pavement industry are facing today.

The rapid escalation in crude-oil prices over the past 18 to 24 months is having a significant effect downstream, as the costs of petroleum-based products, including asphalt, rise accordingly. Figure 1 shows the producer price index for asphalt and concrete, along with the consumer price index; the scale of this situation is self-evident upon examining this data, particularly over the past six months. It was recently reported that asphalt prices ranged from $209 per ton in Denver to $628 per ton in Baltimore. The news of pricing and supply concerns, traditionally limited to trades, are now finding their way to the headlines and airwaves across the country as agencies, large and small, struggle with their loss of buying power due to the cost of asphalt materials and their impact on maintaining a roadway network.

Increasingly, agencies are specifying concrete pavements, not only because of their well-known reputation for long-term ownership cost advantages, but also because they now cost less than asphalt initially. Even some agencies that did not traditionally specify many concrete pavement projects have turned to alternative bidding to allow the market to determine the pavement selection. The good news to the concrete industry is that more often than not the concrete alternatives are winning these competitions.

Do we welcome this new playing field and a stronger competitive position? Of course. We also recognize, as we always have, that the merits of our product must be considered against the competition in order for the taxpayers to receive the best value for the taxpayer dollars that go into transportation. The better news than our new-found cost advantage is that the traditional strengths of concrete pavement, including durability, safety, versatility, and toughness are making the conclusion even clearer: Concrete pavements are the right choice, right now.

Concrete pavements are gaining wider acceptance as agencies and contractors search for solutions to meet sustainable development requirements. We felt it was important to provide a snapshot of some of the current research and technology initiatives, as well as some recent achievements.

Recent history

In September 2005, the National Concrete Pavement Technology Center (CP Tech Center), seated at Iowa State University in Ames, Iowa, published the Concrete Pavement (CP) Road Map, which is a comprehensive and strategic long-term plan for concrete pavement research, prepared with broad industry participation under the sponsorship of the Federal Highway Administration.

The CP Tech Center is an independent, third-party organization that represents the research and technology transfer needs of the concrete pavement community. It also is unique among research centers in that it has the established goal of collaboration with universities and other organizations across the country to leverage the best minds and expertise.

Today, the CP Tech Center and the Concrete Pavement Road Map are managed by executive and advisory boards consisting of private-sector, public-sector and academic leaders who have demonstrated expertise and experience in concrete pavement engineering.

When published, the CP Road Map consisted of 12 research tracks. Although it was decided at that time that sustainability must be an inextricable component of each of the 12 tracks, the ever-sharper focus on sustainability worldwide led the CP Road Map’s executive committee to create a separate sustainability and environmental track in September 2007.

The track is currently under way and is being advanced by a leadership group, which is developing a track framing document to guide research and outreach, as well as to select projects for immediate and future funding, all with the goal of advancing the sustainability of concrete pavements and building on concrete’s already strong position as the most sustainable of the competing pavement materials. This track will closely align with the 12 other CP Road Map tracks to ensure a coordinated and comprehensive effort to address sustainability.

Inherent to increasing the sustainability of concrete pavements is the need to increase energy efficiency, both in the production and operational phases of the pavement’s life.

Current and future research that directly or indirectly increases energy efficiency during the production phase includes:

  • Development and adoption of new recycling methods for concrete pavements to further advance the means through which existing materials may be reused;
  • Development and adoption of advanced construction testing and monitoring to assure the quality of the end products as more sophisticated and complex material combinations are implemented;
  • Development and adoption of advanced, highly efficient equipment, as well as methods for evaluating and improving constructability to ensure that contractors operating under the low-bid procurement process have the technology and capability to achieve specified results;
  • Optimized aggregate sizing to reduce cement content to reduce the energy embodied in concrete;
  • Increasing fly-ash and slag contents in pavement concrete to advance the extent of reuse of these by-products for cement substitution;
  • Two-lift slipform paving construction to allow further use of locally available aggregate that may be acceptable in the lower region of the pavement, but not near the surface;
  • Development of practices to reduce and eliminate construction waste and increased use of recycled water as further improvements in sustainable construction practice; and
  • Development and adoption of advanced, highly efficient equipment to minimize fuel consumption and emissions generated during construction.

In addition to improvements during the construction phase, improvements in energy efficiency during the operational phase are being targeted. These include improvements that may be realized through the maintenance, rehabilitation and recycling operations and those that directly benefit the highway user and surrounding communities.

Current and anticipated research that addresses improvements in energy efficiency during the operational phase includes:

  • Increased pavement longevity, minimizing future maintenance and reducing user costs and delays resulting in significant energy savings;
  • Fast-track repairs and rehabilitation of concrete pavements to reduce construction time and congestion and associated wasted energy from vehicles delayed through work zones;
  • Precast pavements/slabs for rapid repair and replacement;
  • New and improved in-place recycling techniques that save energy by eliminating any need to transport materials to and from a crushing and processing facility;
  • New concrete overlay techniques that extend pavement life with the least amount of materials and energy expended, while also providing the energy-related advantages of concrete pavement surfaces over common asphalt overlay surfaces;
  • Lower rolling resistance, which increases the fuel efficiency of vehicles operating on the pavement surface;
  • Highly reflective surfaces that require less illumination, saving lighting energy and lives while lowering energy required for cooling urban areas;
  • Optimized textures that reduce tire-road noise, maintain frictional characteristics and provide pavement demarcation to improve aesthetics and community acceptance;
  • Photocatalytic surfaces to treat air pollution, lowering energy required for alternative treatment strategies; and
  • Pervious concrete surfaces that eliminate energy consumed to treat point source runoff.

In addition to the research efforts at the CP Tech Center, ACPA also is working closely with researchers at Arizona State University (ASU) to better understand how pavement designs and materials contribute to surface temperature changes. Begun in 2005, this research was designed to identify mix design factors that could allow production of cooler pavement surfaces and a modeling tool by which to evaluate the surface temperature changes. This work will provide further awareness of the urban heat island issue and influence municipal ordinances and building codes to adopt environmentally appropriate materials and solutions.

In pursuing this research, ASU has developed a simplified laboratory test method to evaluate the thermal conductivity of paving materials using conventional construction techniques. ASU also collaborated with ACPA to develop infrared images and place in-pavement sensors for a concrete overlay of an existing asphalt concrete parking lot in Rio Verde, Ariz. This collaboration provided dramatic information about concrete pavement’s benefit in reducing urban heat island effects in a living community.

While we recognize that there are many challenges surrounding our country in these volatile economic and political times, the concrete pavement industry can look to a bright future. It is an exciting time. I can remember a conversation at the beginning of my career, in which two engineers argued the merit of whether concrete pavement was an out-of-date product that didn’t meet today’s needs. Perhaps the tables have turned as more is being asked from our pavement systems than was 20 years ago. What an interesting reflection it is to see more agencies and consultants turning to the concrete pavement industry for solutions to their needs; what a wonderful challenge it will be to answer the call and rise to the challenge. Much work is to be done as new people engage our industry. Of course, more research is needed to explore the opportunities and challenges that lie ahead, but recent research and technology achievements, along with the inherent cost and performance advantages, are ensuring that concrete pavements are “the right choice, right now.”

About The Author: Voigt is president and CEO of the American Concrete Pavement Association, Skokie, Ill.

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