Sample Chapter – Evolution of Road Building Materials

Sample Chapter
Short History of Roads and Highways
Chapter title – Evolution of Road Building Materials

The first roads developed from well used places like stream and river fords, mountain passes and other high traffic areas. From there these early roads most likely followed game trails and natural features of the land. Sometimes extensive networks developed which connected settlements for trade and travel, though they were little more than dirt paths in most cases. The predominant traffic on these early roads would have been foot traffic. Later on horses with travois and then wagons would have used them.
Ridgeways
Early roads tended to follow hill ridges, as these natural features were already well drained and usually have less dense vegetation. The soil is usually already exposed from wind action and already densely packed. These roads have come to be called ridgeways. They developed above flood plains, marshes and swamps and were important in human history as conduits of trade and communication. These primitive roads tended to follow the tops of hills where wind, rain and other environmental factors had eroded away the topsoil, exposing harder, rocky subsoil, rocks and boulders. The roads mostly stayed on the southern side of hills, probably because the increased exposure to sunlight made them warmer and dryer and less exposed to the weather. Ridgeways only descended into valleys when it was necessary to cross a stream or river. Inclines tended to be steep because little, if any, excavating was done. The road’s route could vary considerably on large, rounded hills as the ridgeline was wider there and people tended to follow the easiest route, which could change with weather conditions. Loads on the two wheeled carts in use at the time tended to shift during ascents and descents, necessitating constant adjustment of the cargo.
Dirt Roads
Dirt roads were among the earliest roads used by humans. Most began as game trails that humans began using and expanding. Sometimes extensive networks of these roads developed. At first there would have been no improvements to these roads, however, over time men would clear trees and create fords across streams. Also called dry weather roads or mud roads, these types of unimproved roads still exist, mostly in rural areas in the United States. In other countries they may be the only route into certain areas. Generally passable only in dry weather, the roads vary as to quality due to whether they pass over clay, loam, sandy or rocky soil. They tend to become hard packed over time and subject to erosion during rainy weather.
Timber or Corduroy Roads
The timber, or corduroy road, was one of the earliest improvements to the mud, or dirt, road. Simple to construct, they consisted of a series of logs laid side by side on the ground. The logs sometimes shifted in position, creating a hazard to horses traveling on one. They were mainly used in low, wet areas to provide a solid roadbed.
Plank Roads
To build a plank road, workers first graded and leveled the dirt road. Once level, they then laid a log superstructure lengthwise along the course of the road. Once the foundation was in place, they filled in between the logs with gravel or dirt to support the planks. They would then cut two to three inch thick wooden planks and lay them along the top of the superstructure, nailing them down. Workers dug ditches along both sides of the road to carry rain water away. They would also build plank bridges to cross streams. The finished road provided a much improved traveling surface. The sound of the horses’ hooves clip clopping along the surface made a sound similar to high heels walking on a modern boardwalk. Sometimes the vibration of the horse’s hooves would work some of the nails loose, creating a plank that flopped up and down as horses and wagon wheels traveled along. During the wet season, this “log action” would catapult mud up and over both horses and travelers.
Stone Paving
Archeologists have discovered the first known paved streets in the Middle Eastern region of Mesopotamia. The Sumerians, Assyrians and Babylonians dominated the region at different times. The oldest roads found to date are at the Tell Arpachiyah in Northern Mesopotamia which dates from 6100 to 5400 BC. The earliest paved streets were in cities where heavy traffic soon churned the streets into clouds of dust or rivers of mud, depending upon the weather. It was up to Darius of Persia to build the first long, paved roads.
McAdam and Telford Roads
Telford Road
Scottish engineers Thomas Telford and John Loudon McAdam developed a simple, more economically built road in the early Nineteenth Century that revolutionized the road building industry. Telford scientifically analyzed road traffic, alignment, slopes and stone thickness to design a better road. His design eventually became universal. A Telford Road was expensive to build, as it required skilled stonemasons to lay the foundation of the road. Maintenance of these roads was also expensive. However, John Louden McAdam used many of the principals developed by Telford to design his road.
McAdam Roads
John Loudon McAdam improved on this system by designing a road constructed using a base of crushed, coarse stones overlaid by smaller, crushed stones. Vehicular traffic would pack this crushed stone tightly, allowing it to shed water instead of absorbing it. This kept water from penetrating the surface and allowing frost to break up the roadway. The center of the road was graded to be higher than the edges, allowing water runoff into ditches constructed along the outer edge of the roads. This “McAdam” road soon became recognized as a superior road and its use became quite common by the late 1800’s. The Boonsborough Turnpike Road was the first recorded McAdam Road in the United States, constructed between Hagerstown Maryland and Boonesboro Maryland in 1823. Many consider the McAdam Road to be the biggest advance in road building since the great roads of the Roman Empire.
Thomas Telford (August 9, 1757 – September 2, 1834)
The son of John and Janet Jackson Telford, Thomas was native to Glendinning, Westerkirk, Scotland. At fourteen years of age he apprenticed to a stonemason. In 1782 he migrated to London, England where he fell into company with architects Robert Adam and Sir William Chambers. Telford, who had little formal education, helped build some additions to the Somerset House in south-central London. After this project, he began designing and building his own projects. In 1787 he gained the position of Surveyor of Public Works in Shropshire, England. In this position, he designed several bridges and roads. His reputation as an architect led to his appointment as manager of the construction of the Ellesmere Canal. At the conclusion of this project he went on to design many other bridges and act as a consultant to the King of Sweden on a canal project in that country. He gained his best reputation as a builder of roads, leading to the nickname ‘Colossus of Roads,’ bestowed by the poet Robert Southey in reference to the statue on the Greek island of Rhodes, named the Colossus of Rhodes.
John Loudon McAdam (September 23, 1756 – November 26, 1836)
The son of James and Susanna Cochrane McAdam, John was native to Ayr, Scotland. His family was of the minor gentry class. The family lived in Lagwyne Castle until a fire destroyed it, after which they moved to Blairquhan Castle. McAdam received his education at the McDoick’s School of Maybole, which he attended until he was fourteen years old. In 1770 his father’s business, the Bank of Ayr, failed, taking the family fortune with it. His father died shortly thereafter and he went to live with an uncle, a wealthy merchant, in New York. During the years of the revolution, McAdam supported the British. During the war he became a partner in a privateering ship, the General Matthew, which captured rebel ships and confiscated the cargo. They would then sell the captured cargo, pocketing the profits. He became quite wealthy in this activity, but at war’s end most of his assets were seized and New York authorities put him and his family on a boat for Scotland. He had salvaged enough wealth to purchase an estate in his home town of Ayr. Family links with the 9th Earl of Dundonald gave him part interest in an iron foundry and a company that made products from a byproduct of coal, tar. The need to build better, cheaper roads on his estate led to an interest in road building. He began experimenting with different methods of road building. By 1819 he had written two papers on road building, Remarks on the Present System of Road-Making and Practical Essay on the Scientific Repair and Preservation of Roads. His construction methods emphasized good drainage and carefully grading of the roadbed before and during construction. His roads, cheaper, quicker to build and easier to maintain, became a hit. Soon, McAdam Roads became the standard road all over the world.
Asphalt Roads
The word asphalt derives from the Middle English word asphalte, which was in turn of French origins. The French word derives from the Latin word asphalton or asphaltum. The Romans adapted the Greek word ásphaltos to name the substance.
Sources
Asphalt comes from a variety of sources. Natural deposits of asphalt occur in lakes exposed on the surface. Other deposits occur in natural seeps called tar pits. Oil sands in Canada and Utah also form rich deposits.
Historic Uses for Asphalt
The Babylonians have the first recorded use of asphalt as a road covering. King Nabopolassar (c. 658 BC – 605 BC) used the material in 615 BC. Historians can date it from an inscription on a brick that is part of the Procession Street of Babylon Nabopolassar had constructed from a mixture of asphalt and burned brick. The Sumerians used asphalt as a mortar to seal the cracks between building bricks. Bitumen, a form of asphalt, found use as one of the substances the Egyptians used to embalm mummies. European shipbuilders used pitch to tar ships to make them seaworthy.
Modern Road Building
An Englishman, Richard Tappin Claridge, received the first patent for road building on November 25, 1837. Many roadbuilders began using tar to cover McAdam Roads to cut down the dust raised by wheels crossing over gravel. This type of road became known as the “tarmacadam” pavement.
In the United States
The modern asphalt road was developed at Columbia University by a Belgian emigrant named Edward de Smedt. He developed an asphalt mix which was well suited for road construction. Roads using his methods was in Battery Park and on Fifth Avenue in New York City in 1872. Called by various names, including asphalt pavement, blacktop, tarmac, macadam, plant mix, asphalt concrete, or bituminous concrete today about 94 % of roads in the United States have an asphalt covering.