The first concrete pavements
were placed in 1892 & 1893
Early 1900’s:
May surprise people to know that the first documented use of concrete to resurface pavements dates back to 1901!
That first concrete overlay was
1 of 15 placed between 1900 and 1915!
Although overlay technology has been around for more than a century, the focus of the first half of the 20th century was on building new highways, including the Lincoln Highway, Route 66, the Interstate Highway System, and other roadways and airports that linked our rapidly growing nation.
As the U.S. road network finally took shape, a new challenge emerged for highway engineers to address pavements that were exceeding their original design lives. Finding cost-effective solutions to keep the road network going has been a constant challenge since the 1970s. According to the National Concrete Pavement Technology Center (CP Tech Center), concrete overlays offer cost-effective, versatile, short- and long-term solutions for the full range of concrete, asphalt, and composite pavement needs and contribute to more sustainable construction practices by preserving pavement service for several decades beyond its original design life.
1970’s:
Concrete overlay solutions came into sharp focus during the 1970s:
— 4 overlays placed in Iowa by the Jackson Construction Company (now Cedar Valley Construction)
— Detroit, Michigan, USA Project – Largest fiber-reinforced concrete overlay project to date at that time: 3-in.-thick concrete overlay placed on 4 of 8 lanes on a highway carrying 100,000 vehicles per day
— 41-test-section/storied test site and a comprehensive experiment on fiber-reinforced concrete in Greene County, Iowa. In 1973, the Iowa Highway Research Board, Iowa Concrete Paving Association, and American Concrete Pavement Association (ACPA) planned the test site and, in partnership, facilitated the research. Comprised of 2-, 3-, and 4-in. sections built with fibers and without fibers, the site(s) became a de-facto proving ground for research and technology development that drew national and international attention for many years.
These construction & research projects raised interest in concrete overlays & created demand for the technology
that became known as “whitetopping”
& “ultra-thin whitetopping”—overlays under 6 in. thick
Thereafter, the use of concrete overlays increased steadily for a number of years—but soon, all that would change …
Advancing Concrete Overlay Technology
2000’s:
Following an ACPA-led initiative to coalesce concrete pavement research throughout the country, the CP Tech Center was founded in 2005 to serve as a hub for concrete pavement research and technology.
Since 2005, the use of the overlays has risen from
about 3-4% of the volume of concrete pavement placed annually across the U.S. to an average of >12%
Initially financially supported by the concrete, cement, ready-mix sectors, and cooperative research projects, the CP Tech Center worked to develop resources to meet the increasing interest in this technology. With input from ACPA and other stakeholders, the publication “Guide To Concrete Overlays”, now in its 3rd edition, and other resources continue to provide agencies, engineers, and contractors with useful practical information about how to apply concrete overlays to address almost any existing pavement condition; determining candidate projects; and gaining insights into materials, typical sections, and important construction details.
Gerald F. Voigt, P.E., President and CEO-ACPA said, “The increased acceptance of concrete overlays was a direct result of ACPA and the affiliated chapter network working closely with the CP Tech Center to develop resources and make information available to agency/owners, engineers, and contractors. Federal Highway Administration (FHWA)’s support of these technology transfer efforts has been very important. The use of concrete overlays for pavement resurfacing has been responsible for an increasing share of the concrete pavement usage for well over a decade. Overall, concrete pavements helped ease the industry through challenges such as the Great Recession of 2008 and the global pandemic. Overlays are expected to be a steady and stable market moving forward.”
“Engineers are selecting concrete overlays for almost any type of existing need—from failed asphalt pavement to old concrete sections. Year over year, the most common application is now concrete over distressed asphalt (sometimes called BCOA). Owners are increasingly specifying concrete for projects after many years of the perception that the only option was another asphalt overlay. We are seeing a proliferation of concrete overlays in every market—not just highways—including airports, high-capacity and low-volume streets, and industrial areas,” said Voigt.
He added that the marketplace is seeing more thinner designs that are 6 in. thick or less, therefore shorter joint spacing.
More concrete overlay designs are calling for:
— 6-ft x 6-ft squares
— shorter joint spacings
— slabs that are more resistant to bending
— therefore stronger
He believes such demand is being driven by a greater awareness of the technology and desire for more sustainable and resilient pavement solutions: “The traveling public is increasingly intolerant of frequent repair and replacement cycles because it’s not just the cost of the repairs—it’s also an awareness that those processes require tax dollars, fossil fuels, and often excessive traffic delays and disruptions.”
The application of concrete overlays has reduced the frequency of required replacement or repair to a roadway. As a result, traffic impacts, shutdowns, lane closures, and the danger of exposing workers and motorists to construction work zones have all been significantly reduced.
Milestones & Critical Needs—EDC’s TOPS
2020 was a pivotal year for the continued advancement of concrete overlays, despite the ongoing struggles associated with the COVID-19 pandemic and its impacts on our industry. “We are very pleased that in late August 2020, the FHWA announced that overlays have been selected by the agency’s Every Day Counts (EDC) Program for rapid deployment. The inclusion of concrete overlays in EDC’s targeted overlays pavement solutions (TOPS) as one of the innovations [for 2020/2021] means added visibility for the technology and recognition for the agencies that are using overlays to address challenges and opportunities creatively,” Voigt said.
FHWA describes its intent to shine a light on ‘solutions for integrating innovative overlay procedures into practices that can improve performance, lessen traffic impacts, and reduce the cost of pavement ownership.’ Pavement overlays were one of seven innovations recognized in the current round. Approximately half of all infrastructure dollars are invested in pavements, with more than half of that investment is in overlays. By enhancing overlay performance, state and local highway agencies can maximize this investment and help ensure safer, longer-lasting roadways for the traveling public.
The EDC program points to the many benefits of concrete overlays:
— Safety gains
— Cost savings
— Performance
— Improvements to design methods, interlayer technology, slab geometry, and concrete mixtures
— Broadened concrete overlay surface treatment applicability, reliability, sustainability, and cost-effectiveness
Contributing to the acceptance and increased use of concrete overlays have been a number of tools and resources:
— Overlays Guides—1st, 2nd, & 3rd Editions (CP Tech Center)
— Printed resources (CP Tech Center)
— Webinars (CP Tech Center and ACPA)
— Additional material (CP Tech Center)
— PavementDesigner.org: Concrete and cement industries’ concrete pavement thickness design portal
• FREE
• Different design solutions for parking areas, streets, and intermodal facilities
• No user ID or password needed, but registered users can save designs to a cloud account
— ACPA’s National Concrete Overlay Explorer
• Web-based resource
• Provides details about more than 1,200 projects
• Searchable by overlay type, application by market, pavement thickness, locations in 46 states, and Alberta, Canada
• Project size
• Joint spacing
• Reinforcement
• Construction photos
• Finished project photos
— ACPA’s Applications Library hosts dozens of digital device apps
Going Forward: Keeping up the Momentum
OUTREACH FORUMS: There is still work that needs to be done, and work is continuing on many different fronts. Voigt notes that forward movement will continue to come through sharing and outreach forums like the Concrete Overlay Summits that have become an annual event (held virtually last October) … bringing together all interested in further advancing concrete overlay technology.
RESEARCH & TECHNOLOGY EFFORTS continue in …
• Fiber reinforcements
• Fabric interlayer technology
• Cement technology
• Other materials technology
• Equipment advances
• Testing instrument advances
• Performance-engineered mixtures (PEMs)— the PEM initiative, led by FHWA with support from key industry and agency stakeholders, holds great promise for helping concrete pavements perform better under any application, including overlays. PEM is aimed at implementing what is known, refining performance monitoring and specification refinement, and measuring and relating early-age concrete properties to performance. The initiative has already had some early success, including advancing testing to reach beyond traditional slump, strength, and air measurement and focusing instead on new approaches to strength and concrete workability.
Voigt said, “The goal of PEM is to enable contractors to achieve consistent quality in concrete mixtures, and in turn, to deliver reliable concrete pavements every time, all the time.”
It is a lofty goal, but one that many industry professionals see as an important step in advancing to another 100 years of quality concrete overlay projects. Achieving that goal could mean that a growing number of overlays could still be in service in the next century.
For the Roads & Bridges article titled “CONCRETE OVERLAYS HAVE A LONG AND SUCCESSFUL HISTORY OF BETTERING OUR ROADWAYS AND ADVANCING OUR INDUSTRY”, please go to: www.roadsbridges.com/concrete-overlays-have-long-and-successful-history-bettering-our-roadways-and-advancing-our?amp
LINKS:
CP TECH CENTER CONCRETE OVERLAY: WEBINARS ON DEMAND, GUIDES, MANUALS, TECH BRIEFS, REPORTS, & CASE STUDIES: https://cptechcenter.org/concrete-overlays/
PEMs – FHWA: https://www.fhwa.dot.gov/pavement/materials/hif20005.pdf
https://www.fhwa.dot.gov/pavement/asphalt/trailer/pemd.cfm
PEMs – CPTech Center: https://cptechcenter.org/performance-engineered-mixtures-pem/