Concrete and asphalt compete as building materials in several applications, especially as pavements for highways, roads, driveways, paths, and sidewalks.
Working with asphalt and concrete can be challenging. Both have narrow working temperatures that are much higher than ambient temperatures, and both have a limited-use time once mixed.
Both perform the same job, but specific material qualities are factors in preference for specific projects.
A brief history of road construction
A lot of pavements are roads and highways, and asphalt has a long history with road construction. Babylonians began applying asphalt to stone paths 2500 years ago — they had previously used asphalt as a waterproofing agent but then learned they could improve roads by applying it like a mortar.
Two men from Scotland are responsible for originating our modern asphalt roads (and they coincidentally did it independently of each other, around the same time. Soon after, a man named John Loudon McAdam (https://en.wikipedia.org/wiki/John_Loudon_McAdam) created a better asphalt pavement consisting of stones and asphalt. He called the pavement "tarmacadam."
Although concrete is older than asphalt by several thousand years, and concrete served as a building material in everything from floors to pyramids, nobody used it for roads until the 19th century.
In 1891, George Bartholemew (https://en.wikipedia.org/wiki/George_Bartholomew_(inventor)) convinced the City Council of Bellefontaine, Ohio, to use his concrete mix design to pave a local road. (The U.S. first started paving roads with asphalt about two decades earlier.) Bartholemew guaranteed the concrete pavement would last at least five years. On the street’s 100th anniversary, the city erected a statue of Bartholemew with a plaque that reads: “Here started the better roads movement.”
The case for asphalt pavements
Fast forward to today, about 94% of America’s roads are asphalt, according to the Virginia Asphalt Association. (https://vaasphalt.org/)
Asphalt is comprised of bituminous oil, sand and gravel. Asphalt roads provide several advantages, such as:
Faster curing times: Asphalt cures faster than concrete; faster curing times result in streets and highways being open to traffic sooner.
Better traction: Skid times are shortened on asphalt compared to concrete.
Less noise: The sound of tires rolling on asphalt is decreased compared to driving on concrete.
Better heat absorption: Ice covering asphalt melts faster than ice covering concrete, so the risk of vehicular accidents caused by vehicles sliding on ice is less on asphalt roads.
Flexible during freeze-thaw cycles: Asphalt has flexibility, so its ability to expand and retract during freeze-thaw cycles leads to less damage.
Better with salt: Salt damages asphalt less than concrete.
Decreased placement costs: The cost of laying a single lane mile of asphalt costs less than covering the same area in concrete. Governments own the most roads and highways, so short-term thinking guides many decisions.
Easy to repair: It’s easier to patch asphalt than concrete (although newer concrete repair solutions have significantly narrowed that gap).
Asphalt is easier to recycle: You can recycle asphalt in place and then repave the road with the asphalt you just milled.
The case for concrete pavements
Concrete consists of sand, aggregate, water and cement — a binding agent composed of lime, silica, alumina, and gypsum. Concrete pavements provide the following benefits:
Concrete is strong: Concrete keeps its structure unchanged when under loads that would cause grooves or dents in asphalt.
Longevity: Concrete pavements last about two decades before rehabilitation is required, whereas asphalt roads require on average rehabilitation after just 13 years.
Little maintenance: Concrete pavements require little maintenance compared to asphalt roads.
Concrete keeps its shape: Asphalt can melt during very hot, sunny days, whereas concrete isn’t affected.
More resistant to oil damage: Asphalt will soften and weaken when in contact with oil, but concrete remains largely unaffected.
A variety of colors: Concrete reacts well to stains and dyes, so you can change the color of concrete roads, whereas asphalt roads are always black or dark grey.
Decreased total cost of ownership: A well-maintained concrete road will cost less over the road’s lifetime compared to an asphalt one.
Fewer potholes: The number of potholes — every driver’s worst enemy — is significantly less on concrete roads and highways.
Regardless, both asphalt and concrete are great pavements. Either way, however, there’s a host of repair and maintenance duties that must happen to keep the pavement in good working condition.
