Introduction
In 1889, in the true spirit of American innovation, George W. Bartholomew proposed the first concrete pavement to city officials of Bellefontaine, Ohio. Although the first automobile would not appear for another ten years, Mr. Bartholomew was convinced that the cement he was producing in his small laboratory could be used to produce a hard, durable paved surface.
After two years spent convincing citizens and city officials and by agreeing to donate all the materials, Mr. Bartholomew received permission to build America's first concrete pavement. There was a stipulation - he had to post a $5,000 performance bond and guarantee that the pavement would last for five years.
Completed in 1891, the first section of concrete pavement, an 8-ft.-wide strip of Main Street along the side of Bellefontaine's Courthouse Square, was an immediate success. Local businessmen petitioned to have the entire block around the Square paved with concrete. In 1893, Court Avenue and Opera Street were paved. Columbus Avenue and the remainder of Main Street followed in 1894. The 1894 project was built by William T.G. Snyder, a Bellefontaine roadbuilder and America's first concrete paving contractor.
Mr. Snyder used wagons with teams of horses to haul the cement, gravel and sand to the paving site. As the term "concrete" had not come into use, the "artificial stone" was mixed with shovels and placed into 5-ft. square forms. The surface was scored to give better footing for horses. With these techniques, a new product and industry were born.
As word of success spread, a number of cities began to build concrete roads. Until then, roads were dirt or paved with bricks or poor quality macadam. Most paved roads were in the cities - none in the country. That would soon change, however, as Americans took to the highways.
Automotive Influence
With the 1908 introduction of the first mass-produced automobile, the "Model T" Ford, Americans began taking to the roadways in ever increasing numbers. Local governments responded to constituents' demands for better roads. In 1913, 23 miles of 9-ft.-wide, 5-in.-thick concrete pavement was built near Pine Bluff, Arkansas. As it cost one dollar per linear foot to build, it became known as the "Dollarway." Motorists came from many miles to drive the smooth pavement and to run their automobiles up to 45 mph. It is reported that motorists actually brought their automobiles to Pine Bluff on railroad flatcars to spend a day or two speeding up and down the Dollarway.
A final tour of transportation duty: In early paving operations, horses were called upon to help power the era of concrete streets and roads...and the automobile.
Early dump truck hauls materials to paving site.
In 1914, commissioners from Lee County, Mississippi, traveled by train to Wayne County, Michigan, to scope concrete roads. Upon returning to Mississippi, the commissioners authorized the construction of 49 miles of rural county roads.
Government was responding to the needs of the citizens and a growing nation. By 1914, portland cement had been used to pave 2,348 miles of roadway. America was getting out of the mud.
Rensselaer County, New York, 1908 -- Rural-road users were quick to appreciate what a little concrete could do for farm-to-market thoroughfares.
The introduction of motorized vehicles in the early 1900's also changed the way concrete roads were built. Horse-driven wagons were being replaced by motorized vehicles. In1905, the first "dump truck" was manufactured. Cement and aggregate were dry mixed, then transported to the paving site. A truck-mounted mixer batched the concrete and spread it on the grade between forms. Vibrating strike-off machines screeded and consolidated the concrete.
Two Firsts in 1916
While the advent of the automobile accelerated the nation's desire for better roads, it was another segment of transportation users - bicyclists- who were the most organized and effective in promoting and advocating better
roads. In 1902, the League of American Wheelmen helped organize the American Road Makers. In 1910, the organization was renamed the American Road Builder Association and became a strong advocate for better roads at the Federal level.
In 1916, President Woodrow Wilson signed the first "Federal-Aid Highway Act" directing the federal government to cooperate 50/50 with states in road building. The states needed a professional highway department to be eligible for federal funds and had to maintain the federal-aid road once it was competed. Three years later, Oregon became the first state to level a fuel tax on gasoline, a course soon followed by many states. During the 1920's and 1930's, $2 billion for federal-aid road construction was authorized.
The Portland Cement Association was also organized in 1916, having previously been called the Association of American Portland Cement Manufactures. Improving and extending the use of portland cement for road building became a major goal of the Association and the cement industry and remains one of the primary efforts of PCA today.
Problems Spur Innovations
In the 1930's, two significant forms of distress began to appear in concrete roadways. A number of states started using de-icing salts to remove ice and snow from pavements. About the same time, surface scaling developed on many pavements in northern climates.
Extensive research was undertaken by PCA and several state highway departments to determine the cause of the distress. The studies found that freeze and thaw cycles, accelerated by the use of de-icing salts, were causing the problem.
In one series of PCA investigations, concrete samples made from different cements were exposed to accelerated freeze-thaw testing. Concrete made from one particular cement showed markedly better freeze-thaw resistance then other samples. Upon microscopic examination, investigators found that concrete made from this cement contained billions of minute air bubbles.
Researchers were stymied as to the source of these air bubbles. They visited the cement plant to look at the manufacturing process. They discovered that the beef tallow that had been added as a grinding aid was unintentionally producing an air-entraining cement. Soon after, aid-entraining cement and admixtures found their way into concrete pavement construction specifications and surface scaling was virtually eliminated. During the 1920's and 1930's, after
Major durability concerns surrounding concrete pavements exposed to deicer compounds were laid to rest with the late - 1930s identification of the effects of air-entrainment. Here, a microscopic view of a polished section of concrete shows well dispersed bubbles or voids.
the topsoil was removed, concrete pavement was usually constructed directly on the underlying soil. This was satisfactory until highway truck traffic began to increase in the late 1930's. Pumping distress began to appear on roadways carrying heavy truck traffic.
Pumping, as it was defined by PCA and a special Highway Research Board Committee, is the forceful ejection of waterborne subgrade soil during the passage of heavy wheel loads. Further investigations showed that three conditions were required for subgrade pumping:
A subgrade soil containing fines that will go into suspension
Free water between pavement and subgrade, or subgrade saturation
Frequent passage of heavy axle loads
Three 34E on-site mixers supply a paving train on an early interstate project.
When pumping conditions were found to exist, it was recommended that a non-pumping layer called a subbase be placed under the slab. Gravel, crushed stone, and slag were commonly used as subbase material. In the late 1940's, California began using cement-treated granular subbase under concrete pavements. This practice quickly spread to other states.
From 1892 until the late 1940's there was no dramatic advance in concrete pavement construction procedures. Concrete was generally mixed on site. By the mid-1940's, the 34E paver, capable of mixing 34 cubic feet of concrete per batch, was commonly used by paving contractors. Up to three 34E pavers placed concrete between forms for strike-off and consolidation.
The Equipment Revolution
In 1946, two Iowa highway engineers, James W. Johnson and Bert Myers, conceptualized the slip form paver. In the laboratory, a simple device was constructed to slip-form a slab 18 inches side and about 4 inches thick. A 4 foot-wide, 5-inch-thick section of sidewalk was slipformed the following year.
In 1949, the Iowa Highway Department constructed the first slipformed roadway, a 9-ft.-wide, 6-in.-thick section of county road. By placing two lanes side-by-side, a typical 18-ft.-wide county road could be built. The paver attached to a ready mix concrete truck, which would discharge its load into the paver, then pull the paver forward.
In 1955, Quad City Construction Company developed an improved, self-propelled, track-mounted slipform paver capable of placing 24-ft.-wide slabs up to 10 in. thick. In just a few years, several equipment manufacturers were marketing slipform pavers capable of placing concrete up to four lanes wide.
During the same period, central mixing replaced on-site mixing on most paving jobs. Evaluations by several agencies showed that central-mixed concrete could be hauled from the mixer to the slipform paver in nonagitating dump trucks with no loss in workability or quality. Large central mixers could mix 7 to 10 cubic yard of concrete in 45 to 75 seconds.
A vintage 10-foot wide slipform paver: the most significant advancement in concrete paving equipment cropped up in Iowa's 1949 harvest.
It was also during the late 1940's and early 1950's that paving contractors began experimenting with sawed concrete joints. Previously, joints were formed in the plastic concrete with jointing tools. These hand-formed joints often created a rough ride. After early gobs in Kansas and California, sawing was used on several projects in 1951, and soon became a standard construction method.
1956: Bring on the Interstate These new innovations in concrete paving construction techniques were just in time for the largest road construction project in U.S. history - the " National System of Interstate and Defense Highways." Signed by President Eisenhower, the "Federal-Aid Highway Act of 1956" called for 41,000 miles of Interstate roadways at an estimated cost of $41 billion.
Doubling the production, a two-lane slipform paver casts new ground.
Recognizing the opportunity for the use of cement, PCA's membership set a goal of 100 percent concrete construction on the Interstate system. For about five years, $1 million dollars a year was spent on advertising concrete roads in Life, Look, and the Saturday Evening Post. When the 41,000-mile system was complete, about 60 percent of it was concrete.
As the Interstate construction program got underway, highway engineers recognized the need for an improved understanding of pavement performance and design. The AASHO Test Road, a $27-million study, was undertaken near Ottawa, Illinois. Six different test loops were built and loaded around the clock for two years. Twelve different combinations of axles and many thicknesses of asphalt and concrete were evaluated. Performance histories and trends were established.
Design equations evolved from the AASHO Test Road, one for concrete, one for asphalt. These equations, with subsequent modifications and improvements, are the basis for the thickness design procedures of AASHTO Guide for the Design of Pavement Structures. (AASHO added Transportation to its title in 1973, becoming AASHTO.)
PCA's national advertising campaigns for concrete pavements spanned more than five decades, from post-World War I days to the early years of Interstate construction.
Modern, high-production slipform pavers can place and finish wide pavements to a high level of smoothness. Some can automatically implant tiebars and dowels on the move.
The 1960's and Interstate construction also saw a number of advances in concrete pavement construction technology. Electronic controls were added to slipform pavers. Subgrade trimmers were introduced for better grade control. Tied concrete shoulders, first tested in Illinois in 1964, were found to add significant structural value to concrete pavements. Concrete saws were increased in size and capability.
Recognizing the need for an industry spokesgroup to represent the growing number of concrete paving contractors and associated equipment and materials suppliers, the American Concrete Pavement Association was formed in 1964. Today, this dynamic organization represents more than 400 contractors, material suppliers, and others interested in furthering the technology and use of concrete pavements.
Shifting Gears
As the Interstate Highway System came closer to completion in the late 1970's and 1980's, a series of new challenges faced the concrete paving industry. Many roadways needed repair and restoration. In 1976, Congress for the first time approved federal funding for the 3R program - restoration, rehabilitation, and resurfacing. In 1981, a fourth R - reconstruction - was added for Interstate projects.
A variety of concrete pavement restoration techniques (CPR) was developed by contractors during this time. The Federal Highway Administration, AASHTO, ARTBA, and other groups worked closely with the industry to develop standards, specifications, and training programs. Restoration of existing concrete pavements quickly moved from experimental procedures to time-tested, proven techniques.
Equally important was the pressing need to reconstruct portions of our highway system. Again, innovations in concrete paving came to the forefront. Concrete overlays - bonded, unbonded, and whitetopping - offered permanent solutions to troubled pavements. Existing concrete roadways were recycled into aggregate for new concrete.
New demands on concrete pavement have led to material advances. Roadway repairs must be made as quickly as possible for the safety and convenience of the travelling public. New cements and concrete mixtures now allow concrete patches to carry truck traffic in as little as 4 hours after placement.
Innovations in construction techniques have also speeded up major rehabilitation and reconstruction projects. New "Fast-Track" paving techniques and materials, developed cooperatively by state highway agencies, the FHWA, and industry, can significantly decrease the time needed to open a project to traffic. Nondestructive testing techniques are available to accurately determine concrete properties in a rapid manner.
100 Years of Progress
Concrete paving has seen significant advances in the 100 years since the first pavement was placed in Bellefontaine. Changes have come through innovation necessary to meet the demands of the travelling public. Through the spirit of cooperation with government and industry, the concrete paving industry is poised to meet the challenges of the next 100 years.
Moving into the second century of progress, ACPA will continue to foster innovation and enhancements in the products and processes used in concrete paving.
