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Laying the Foundation for Asphalt Roads
Despite these early uses of asphalt, several hundred years passed before European or American builders tried it as a paving material. What they needed first was a good method of road building.
Englishman John Metcalf, born in 1717, built 180 miles of Yorkshire roads. He insisted on good drainage, requiring a foundation of large stones covered with excavated road material to raise the roadbed, followed by a layer of gravel. Thomas Telford built more than 900 miles of roads in Scotland during the years 1803–1821. “He perfected the method of building roads with broken stones, laid to a depth according to the weight and volume of traffic it would have to carry,” Gillespie writes.
Telford’s contemporary, John Loudon McAdam, taught himself engineering after being appointed a trustee of a Scottish turnpike. McAdam observed that it was the “native soil” that supports the weight of traffic, and that “while it is preserved in a dry state, it will carry any weight without sinking.” To construct his roads, McAdam used broken stone “which shall unite by its own angles so as to form a hard surface.” Later, to reduce dust and maintenance, builders used hot tar to bond the broken stones together, producing “tarmacadam” pavements.
Asphalt Roads Come to America
The first bituminous mixtures produced in the United States were used for sidewalks, crosswalks, and even roads starting in the late 1860s. In 1870, a Belgian chemist named Edmund J. DeSmedt laid the first true asphalt pavement in this country, a sand mix in front of the City Hall in Newark, New Jersey. DeSmedt’s design was patterned after a natural asphalt pavement placed on a French highway in 1852.
DeSmedt went on to pave Pennsylvania Avenue in Washington, DC, a project that included 54,000 sq. yds. paved with sheet asphalt from Trinidad Lake Asphalt. The durability of this pavement proved that the quality of the asphalt found in the Americas was as good as that imported from Europe.
Patented Roadways
Builders, quick to see the advantages of asphalt, tried to stake out claims to the material. “Looking back from today’s marketplace, where Hot Mix Asphalt (HMA) is compared and classified only by its technical qualifications, it is difficult to comprehend that until 70 years ago, competing proprietary brands of HMA were peddled, touted, and huckstered with all the enthusiasm that now is used to advertise soft drinks,” writes Gillespie.
The first such patent was filed in 1871 by Nathan B. Abbott of Brooklyn, New York. In 1900, Frederick J. Warren filed a patent for “Bitulithic” pavement, a mixture of bitumen and aggregate; despite vigorous efforts by the Warren Brothers Company to defend its patent (and the name of the material), “bitulithic” was often used to describe any asphalt pavement. Other trade names for asphalt mixes included Wilite, Romanite, National Pavement, Imperial, Indurite, and Macasphalt. Many of these patented mixes were successful and technically innovative.
The fierce competition among asphalt producers, however, allowed cities to require more stringent requirements for their asphalt roadways. In 1896, for example, New York City adopted asphalt paving in place of brick, granite, and wood block. But it also required 15-year warranties on workmanship and materials. The long-term warranties, which did not recognize pavement failures caused by factors beyond the asphalt contractor’s control, bankrupted many builders. The result was fewer and higher bids for asphalt pavements.
The patents for “Bitulithic” pavement expired in 1920, and subsequent improvements in pavements by Federal and state engineers forced most of the remaining patented pavements from the market.
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