One of chief features of concrete pavements is its durability. Concrete pavements often exceed their design lives in applications including highways, airports, municipal streets and local roads. But just how durable are concrete pavements? The answer in at least two cases can be found in concrete pavements that are still in service after 40 to 70 years, in spite of increased loadings.
In Kansas, there is an historic eight-mile stretch of concrete pavement, which was the first completed section of the national interstate system. The Kansas Department of Transportation (KDOT) and Koss Construction Co. of Topeka, formerly of West Des Moines, Iowa, teamed up to construct this section more than 40 years ago.
They then added two lanes to the existing two lanes of US 40 to create I-70, which runs through Wabaunsee County, starting in the town of Paxico about seven miles west of Topeka. The “newest” section of I-70 opened on Nov. 14, 1956, and was the first part of a larger multi-stage job constructed between 1955 and 1962.
As part of the 40-year anniversary celebration of the interstate system a few years ago, Rodney Slater, then-adminstrator of the Federal Highway Administration, now U.S. Secretary of Transportation, and KDOT officials presented an award to Koss Construction for its important role in the construction of this historic first portion of the Interstate Highway System.
Low maintenance, long life
The project originally cost $1.5 million to construct. The highway featured a 4-in. granular subbase (bid at $0.36 per square yard) and 182,679 sq yd of 9-in.-thick mesh-reinforced portland cement concrete (PCC) pavement (at $3.93 per square yard). “The construction techniques were hugely different back then,” said Mike Lackey, assistant secretary and state transportation engineer for KDOT. “Today the quality is more uniform. We’ve learned from our mistakes and we’re much closer to the optimal design for concrete pavement.”
The year the highway was completed traffic per day was 2,310 vehicles. The traffic flow grew to unanticipated levels during the next 42 years. In 1998, an estimated 17,000 vehicles per day—3,000 of them heavy trucks—traveled along the section of interstate. The original section of pavement endured for 38 years before requiring an overlay.
When the interstate was originally constructed, KDOT based the decision to use concrete on the amount of traffic and the availability of materials throughout the state. “Back then, shipping costs were very important, so we used the materials available in a certain area,” explained Lackey.
KDOT does things differently today. “For each project, we do life-cycle costing on several options,” said Lackey. “Over the years, concrete has become much more competitive than in the past.”
Contractors make the difference
“Our concrete pavers are second to none,” said Lackey. “The quality of their work is exceptional. Koss Construction paved the original interstate 43 years ago and they’re still doing exceptional work for us today. What does that say for the integrity and quality of the organization and the concrete pavement industry?”
Don Beuerlein, president of Koss Construction, responded: “In these days of tight budgets and fiscal responsibility, KDOT has managed to put together a highway program that is the envy of the country,” he said. “While other states despair over their lack of funds and resulting weak highway programs, Kansas charges forward building and improving roads that will save lives and provide jobs.”
Not just for highways
Concrete pavements are a logical choice for highways, given the fact that many—if not most—of America’s highways are carrying far more traffic and heavier loads than when they were originally designed. But concrete also is an effective choice for streets and local roads, as evidenced by the city of Sheboygan, Wis., which for the past 80-plus years has made concrete its pavement of choice. In 1955, the Portland Cement Association erected a plaque commemorating the city’s 1.5 million sq yd of concrete pavement.
Tom Holtan, Sheboygan city engineer, estimates this city of 51,000 people now has approximately 4 million sq yard of concrete pavement, or close to 180 miles. That’s not bad considering the city’s street total is 195.21 miles.
“Before the advent of concrete, Sheboygan’s streets were constructed of cedar block,” said Lloyd Reilley. Now retired, Reilley was the Sheboygan city engineer from April 1968 to January 1997. “When I got there, Sheboygan was already a concrete city,” he added.
Built in 1911, North Sixth Street is Sheboygan’s first and longest-lasting concrete pavement. With a few exceptions, all streets have been concrete since then, including all new subdivisions.
The longevity of concrete is recognized in the city’s assessment policy. This policy sets the guidelines under which property owners pay for a portion of the street improvement costs. According to this city ordinance, a property owner cannot be assessed again for at least 30 years after a street improvement is made with concrete pavement. When a street improvement uses asphalt pavement, the owner can be assessed for pavement costs after 15 years.
According to Holtan, the city was so dedicated to concrete pavement it had its own paving crew and equipment until the early ’70s, with two concrete plants operating within the city limits.
The standard PCC pavement thickness has remained 7 in. over the past 88 years. “The mix and the process has changed,” said Holtan. “We used to use 20-ft transverse joint spacing, now we go with 10 ft.” He’s quick to add, “But it’s still 7-in. thick.”
Vinton Construction Co. of Manitowoc, Wis., has done concrete paving in Sheboygan, as well as in other Wisconsin cities. Its president, Jim Maples, pointed out that Sheboygan is not the only Wisconsin city that favors concrete pavement because of its durability and low maintenance. Green Bay, Manitowoc, Oshkosh, Appleton, among other Fox River Valley communities, also use significant amounts of concrete.
Maples recalls how concrete paving has changed over the years. “Back in the ’50s, engineering dictated that concrete pavement must cure for 28 days. Since then, the industry has made great strides and reduced curing time to five days. The invention of the slipform paver really helped, producing a denser product with earlier strengths and an integral curb and gutter system. And now with fast-track mixes you can drive on the pavement the next day.”
Why concrete pavements?
According to Maples, the decision to use concrete pavement in Sheboygan and other Wisconsin cities was based on its inherent low maintenance. “Back in the ’40s, the public works director recognized that concrete pavement required minimal upkeep and he could cut maintenance costs by using a product that lasts 30 or 40 years with little or no repair,” he said. He added that concrete can bridge utility trenches and will resist trench settlements in the road.
“We’re getting 60 to 70 years of life out of our concrete pavement, with the longest-lasting streets being in residential areas,” Maples said. “The answer is the product itself—it’s simply more durable than asphalt pavement.”
Maples applauded Sheboygan’s foresight in choosing concrete pavement in the past and its dedication to concrete for the future. “In addition to its longevity, concrete pavement goes down fast and cures quickly,” he said. “The industry has always found ways to allow immediate access for the public and businesses during construction. And a simple life-cycle cost analysis shows concrete is, in the long run, less costly than asphalt.”
A team effort
Reilley acknowledged the role of the contractor in the success of Sheboygan’s long-lasting streets. “Jim Maples is the dean of concrete pavement,” said Reilley. “His knowledge of the concrete business is phenomenal. An engineer can come up with anything, but someone has to build it. That’s where the expertise and experience of the concrete contractor come in.”
Notwithstanding the history of these and other concrete pavements across the country, there’s more to the story than the durability of concrete alone, according the American Concrete Pavement Association. Technological advances and other improvements such as fast-track paving make it possible for concrete pavements to be constructed and opened to traffic quickly. Other improvements in materials, equipment and processes make concrete pavements safer, smoother, less disruptive to traffic and lower cost.