By John Davis
When World War II and gas rationing ended in 1945, automobile and truck traffic began to increase. Full-scale automobile production resumed in 1946, as well as major road maintenance and new highway construction.
Massive resurfacing programs began but could barely keep up with the demands of post-war travel. By 1950, vehicle registration exceeded 10 million cars and 8.4 million trucks. The asphalt industry was in a good position to meet the demands for new roads, asphalt driveways, parking lots and large-scale recreational facilities.
The restrictions of asphalt during the war years had resulted in a 9 percent drop in shipments of paving grade asphalts. After the war, and the lifting of restrictions on road construction materials, prospects for the asphalt industry looked bright.
In January 1950, Bernard Gray was elected President of the Asphalt Institute. Previously Engineer Economist for the U.S. Bureau of Public Roads and Chief Engineer with the West Virginia Road Commission, Gray’s research writings and promotional efforts were a milestone in launching the use of asphalt for roads and streets around the nation.
Gray’s technical writings, his vast knowledge of road materials, his ability to work with a knowledgeable staff of field engineers and his smooth teamwork with Prevost Hubbard (one of the finest chemical engineers in the asphalt industry) aided in building the Asphalt Institute into the most learned and trusted source of highway construction in the world. The Maine Turnpike was a major breakthrough for the use of asphalt on U.S. highways.
The turnpike era
After World War II, highway travel greatly increased but there was a big gap between the dollars spent for car and truck travel and the dollars spent to build and maintain roads. In 1950 over $10 billion was spent for motor vehicles, compared to $4 billion spent for roads and highways.
Traffic congestion in the cities and suburbs was becoming a major problem, and the American pastime of pleasure driving was almost impossible in some urban areas. The death toll on the highways was tens of thousands per year, and the public was crying out for relief from congested highways.
The source of highway revenue was the gasoline and motor vehicle tax. The critical need for post-war maintenance left little money for new road construction. Highway engineers began looking at turnpikes for possible sources of revenue. The Pennsylvania Turnpike, built during the depression, was a prime example of how to increase road quality and pay for it at the same time. Politicians felt they could abate the public cry for new roads by building turnpikes and paying for them with tolls.
The state of Maine was the first to put the turnpike theory into action. In 1945, Maine’s existing U.S. 1 Highway from Kittery to Portland could no longer handle summer tourist travel. The economy of the state depended on tourists’ easy access to the ocean and vacation areas. To meet the problem, Maine created a turnpike authority and began to let construction contracts.
The Maine Turnpike was a major breakthrough for the use of asphalt on U.S. highways and was a milestone in the Asphalt Institute’s promotional successes. Many of the turnpike consulting engineers had served in the Corps of Engineers during World War II and they were familiar with the high standard of technical and engineering information provided by Asphalt Institute engineers.
State DOT design engineers around the nation had not even considered the idea of using asphalt for high-profile projects such as the Maine Turnpike. Without question, they had thought the turnpike should be built with concrete.
Concrete versus asphalt
The competition from portland cement concrete (PCC) was intense but Maine asked for alternate bids— both asphalt and concrete. The Asphalt Institute recommended a mechanically stabilized gravel base with a dense-graded asphalt surface. The results of the alternate bids showed a marked cost advantage in using asphalt, enough so the entire length of the Maine Turnpike was awarded to asphalt. The first 48 miles of the turnpike was constructed in 1947 and opened to traffic in the fall of that year.
The Maine Turnpike proved that together with a flexible base, an asphalt wearing surface would stand up to any type of traffic loading. During construction and for many years after, engineers from all over the U.S. and the world visited the Maine Turnpike. The full 66-mile turnpike, from Portland to Augusta, opened in 1955.
New Jersey Turnpike
Asphalt Institute engineers were also influential in the decision to build the New Jersey Turnpike with asphalt. The four-to-eight lane highway was built to handle the heavy traffic from South Jersey and Philadelphia to New York City and north.
The same consulting engineers that led the design on the Maine Turnpike were used to supervise the design and construction of the New Jersey Turnpike. When engineers compared bids of PCC and hot-mix asphalt, they saw the New Jersey Turnpike Authority would save $5.5 million dollars by using asphalt, so they awarded every section of the turnpike to asphalt. Construction of the 118-mile turnpike began in 1949 and was opened to traffic in January 1952.
Historically speaking, the decision to build the New Jersey Turnpike with asphalt was of tremendous significance to both the asphalt industry and state DOTs across the country.
The Asphalt Institute had been championing since the 1930s recognize asphalt as the preferred construction material for major heavy-duty highways.
The acceptance of asphalt by highway engineers on the Maine and New Jersey turnpikes persuaded many other states to use asphalt on their turnpikes. Oklahoma, Kansas, Massachusetts, New Hampshire, Connecticut and Florida followed with toll roads, thruways and parkways constructed with asphalt.
Asphalt Institute influence
Extensive writings by Asphalt Institute engineers, such as Hubbard and Gray and the success of asphalt pavements during World War II were positive influences. Extensive discussions at the AI paving conferences, papers presented by the Federal Highway Research Board, as well as asphalt test sections around the country were further proof that asphalt would work on heavy-duty highways.
The Asphalt Institute was able to show consulting engineers that asphalt had the ability to support large vehicle loads yet be constructed with local aggregates. Lower initial costs, speed of construction and lower maintenance costs also persuaded state design engineers to use asphalt on heavy-duty highways and turnpikes.
In 1952, the Western Association of State Highway Officials (WASHO) decided to test the strength of asphalt pavements and asked the Highway Research Board to supervise the test. The test was located at Malud in Southern Idaho. WASHO designed the flexible road sections with varying thicknesses—from 6 to 22 inches and subjected them to repeated applications of 18,000 and 22,000-pound single axle loads and 32,000 pound and 40,000 pound double axle loads. The tests produced four major conclusions:
• Asphalt pavements can carry the heaviest legal truck loads without distress.
• Asphalt pavements can support the heaviest trucks during the critical spring thaw periods.
• Paving the shoulders of asphalt roads will greatly increase the load-carrying capacity of the roadway and reduce maintenance.
• An asphalt surface four inches thick is far superior to an asphalt surface two inches thick.
Shortly after World War II, the federal government and the municipalities began building airports in all parts of the country. Most of them were constructed with asphalt due to lower initial cost and the Asphalt Institute’s valuable technical help given to the Corps of Engineers during WWII.
Later, after the war, AI engineers supplied the Civil Aeronautic Administration (CAA) with critical technical information for our national and international airports.
The interstate system
The Federal-Aid Highway Act of 1956 launched the interstate system and created a national highway infrastructure unmatched anywhere in the world. The heart of the system was a 41,000-mile highway network connecting major population centers across the U.S.
The job of creating the geometric designs for the system was given to the Federal Bureau of Public Roads and the state highway departments. The selection of pavement type was done by the states, so both the Portland Cement Association and the Asphalt Institute began meeting with state highway engineers to tell them about the advantages of concrete and asphalt.
The meetings resulted in many states specifying asphalt for their part of the interstate system. Other states, however, ignored the economy of asphalt and continued their preference for concrete, even though the cost of construction was much higher.
At the end of WWII there were less than 50,000 miles of asphalt highways in the U.S. By 1957, however, this increased to 200,000 miles while concrete roads had declined from 100,000 miles to 80,000 miles during the same period. State highway engineers turned to asphalt overlays because they were the least expensive and most reliable method of renewing interstate highways.
Asphalt for canals, reservoirs, lagoons and swimming pools
The use of hot-mix asphalt for dams, irrigation canals, reservoirs and other hydraulic structures increased rapidly during the early 1950s. After extensive field experiments, the Bureau of Reclamation found that dense-graded asphalt was the best solution for the problem of water seepage in irrigation canals and storage reservoirs. The Ludington Pumped Storage Facility in Michigan, constructed of asphalt, is still one of the largest reservoirs in the world.
But it was not just for hydraulic structures that design engineers were interested in asphalt. Parking lots, swimming pools, recreational facilities, automobile test tracks and speedways were also a rapidly developing market for asphalt.
Full-depth asphalt pavement
In 1962 Duke Beagle, Public Works Director for the City of Woodbridge, New Jersey, began using full depth asphalt on his city streets. He believed that the clay subgrade of Northeast New Jersey could be sealed off by a layer of stabilized asphalt base and be strong enough to support wheel loads without serious deflection.
Beagle laid a 4-inch stabilized asphalt base-course on several of the Woodbridge streets and topped them with a 2-inch surface course. The streets withstood the winter months without cracking or deflection.
The speed of construction and the economy of labor and materials on the full-depth asphalt Woodbridge streets saved 10 percent over the cost of traditional pavements and they performed better. Consequently, the Woodbridge township enacted an ordinance requiring that all streets, including those in private developments, be constructed with stabilized asphalt base on subgrade.
Beagle’s success with the full-depth method aroused national interest in the Full-Depth method—not only in the full-depth design but also in its economic advantages. Asphalt Institute field engineers began discussing full-depth asphalt design with city engineers throughout the U.S.
By the late 1960s, full-depth asphalt was being used by cities all over the U.S. City engineers liked full depth asphalt because it lowered the stress on the subgrade and reduced the total pavement thickness. It could be built faster, easier, and more economically than any other pavement type.
The 1970s saw a national interest in conserving energy and materials and in preserving the environment catalyzed an increasing interest in recycling across the U.S. It was a practical and economical way of reconstructing old pavements and was the hottest new market to develop since the 1960s. Asphalt Institute field engineers began to actively promote recycling and to develop a comprehensive recycling manual.
Road engineers were soon using recycling on interstates, primary roads, county roads and city streets.
The engineering department of Binghamton, New York, had rehabilitated its streets with PCC until 1975. Then the department changed to in-place cold-mix recycling. The recycling technique helped the city get at least thirty-five percent more for its rehabilitation dollar as opposed to the traditional haul and dump method.
The cold-mix recycling in Binghamton was done with a minimum of inconvenience to residents. Streets were closed for a maximum of a few hours over a period of three working days.
Recycling was also the answer to reconstructing the general aviation airport at Red Lodge, Montana. The existing doublechip seal-over-base runway was recycled into a 4.5-inch hot mix asphalt surface. Work was completed November 8, 1978.
By the end of the 1970s, thousands of old country roads around the U.S. were in severe need of reshaping and resurfacing. For conservation and environmental reasons, road engineers began asking for information about asphalt emulsions. Amendments to the Clean Air Act of 1977 required each state to submit its implementation plans to the Environmental Protection Agency (EPA).
The implementation plan drastically reduced the use of cutback asphalts. Consequently, the Asphalt Institute together with the Federal Highway Administration (FHWA) and the Asphalt Emulsion Manufacturers Association (AEMA) developed the “Basic Asphalt Emulsion Manual” and a series of regional workshops to train state and county road personal in the proper use of asphalt emulsions. In many cases, recycling with asphalt emulsion was the ideal solution for rehabilitating a county road, a city street or even a state highway.
The focus of the paving industry changed from new construction in the 1950s and 1960s to rehabilitation in the 1970s and 1980s. Much of the interstate system was nearing the end of its service life by the end of the 1970s and needed repair and rehabilitation.
State highway engineers turned to asphalt overlays because they were the least expensive and most reliable method of renewing interstate highways. Chicago’s John F. Kennedy Expressway, considered one of the busiest roadways in the world, was an example of a large overlay project that was cost-effective and durable.
Originally constructed with 10 inches of concrete, the expressway was experiencing surface deterioration and joint failure. Travel lanes had blown up or buckled in many places due to slab expansion on hot summer days. Carrying more than 200,000 vehicles per day in 1971, the expressway was resurfaced with 244,000 tons of asphalt. That overlay lasted more than 15 years and was in good condition when a second asphalt overlay was completed in 1987.
Rehabilitating concrete with asphalt
Rehabilitating deteriorated concrete highways with asphalt took several forms in the 1980s. The California Department of Transportation (Caltrans), along with Pennsylvania, Ohio and Virginia, found that cracking and seating concrete and overlaying it with asphalt was the most effective method of reducing concrete slab movement and the subsequent reflective cracking resulting from the underlying joints. New York and New England states found that sawcutting and sealing the asphalt overlay above the concrete joints would effectively control reflective cracking.
States in the southeast and midwest cut rehabilitation costs by rubblizing—pulverizing the concrete into small pieces with a resonant pavement breaker, then overlaying the rubblized concrete with asphalt.
The South Carolina DOT, as well as the Ohio and North Carolina DOT analyzed the rehabilitation lifecycle cost of rubblizing and found it was the most economical of the rehabilitation options.
Tennessee and Arkansas developed an effective technique to reduce reflective cracking in concrete joints by using large aggregate asphalt mixes. From the early 1970s into the 1980s the Arkansas State Highway Department effectively used the crack-relief system on more than 300 miles of interstate and state highways.
By the time the 1980s began, the world had changed again and new challenges faced the asphalt industry.
Davis is a contributing editor to Asphalt magazine.