When was the last time you celebrated the existence of concrete?
Chances are it’s not at the top of your curiosity list, but the history of concrete is not as dull as you might think. It’s best not to underestimate the power and ageless strength of one of the most durable compounds known to man, because the legacy and future of concrete is indeed more exciting than many would imagine.
Concrete itself is actually a phenomenon of nature, with the first evidence of its existence in Israel dating back to 12,000 B.C., when natural deposits of cement compounds were said to have formed due to reactions between limestone and oil shale, employing spontaneous combustion.
3,000 B.C. finds ancient Egyptians using mud mixed with straw to bind dried bricks. These geniuses furthered the discovery of lime and gypsum mortar as a binding agent for building the Pyramids. About the same time, the ancient Chinese people used cementitious materials to hold bamboo together in their boats and in the Great Wall, another Wonder of the Ancient World.
Romans began employing slaked lime and volcanic ash called Pozzuolana in 300 BC, named after the town of Pozzuoli, near Mt. Vesuvius. This was a hydraulic cement that hardened with the addition of water, but (hold onto your stomachs) animal fat, milk, and blood were also used as admixtures. Pozzuolana was used for aqueducts and for the Roman Coliseum, built by Emperor Vespasian. The most famous ancient use of concrete is reputed to be the incredible Pantheon in Rome, still considered one of the most historically and architecturally significant buildings of the ancient world, erected in 200 B.C during the rise of the Roman Empire. After 400 A.D., however, the art of concrete was all but lost, when the empire fell.
It wasn't until the middle ages, when people like Joseph Moxon wrote about a "hidden fire in heated lime that appears upon the addition of water" that concrete again comes into focus. And in 1750, English engineer John Smeaton reinvented hydraulic cement to rebuild the Eddystone Lighthouse off the Cornwall coast.
The British furthered the evolution of concrete in 1824, when a Leeds bricklayer, Joseph Aspdin, invented Portland cement, so called because the resulting concrete looked to him like stone quarried on the Isle of Portland. He used limestone road surfacing ground into powder by carriage wheels, added clay, and discovered that, when burned, the mixture could be formed into a uniformly strong cement. Aspdin, by the way, was arrested for shoveling up the "public dust" from the road.
Americans imported European Portland cement for the first time in 1868 and began to manufacture it for themselves in the 1870s. This cement now accounts for most of the world's output of hydraulic cement, and can be ground so finely that it can sift through a screen with 40,000 holes to the square inch. Unlike building materials relying on scarce or non-renewable resources, concrete is made from three readily available ingredients: water, aggregate (stone, sand, gravel) and Portland cement. Green folks can take heart in the fact that cement manufacturing can use recycled materials, even old tires, for fuel. It can be recycled, crushed, and reused as a road base, or used in large chunks for erosion control and fish habitat.
Today's use of concrete can take many forms. For the significance of residential and commercial building, however, concrete is having another heyday at last. It is now the most widely used building material in the world, a signature construction component in skyscrapers, bridges, superhighways and dams, houses and sidewalks. As an "artificial rock" with Portland cement as a required element, concrete protects against fire in homes and public buildings, suffers less damage due to flooding than do similar wooden structures, and has taken huge strides in modern days towards producing earthquake-safe structures.
Hurricane country benefits from concrete block construction, creating "safe" havens from the forces of nature. Insulated concrete-formed homes can account for significantly reduced energy consumption, and a concrete-built home can save 41 trees from their demise.
Any of us having traveled to parts of Europe, Mexico, or South America could attest to the broad use of concrete in new home construction, particularly in countries where wood is one of the rarer natural resources.
Okay, so concrete may never become the topic of lively conversation in the big scheme of things, but it may well be the foundation upon which other conversations take place, remaining long after the last echoes are gone.
For more information about versatile concrete, go to www.cement.org.
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