By Greg Sitek
Concrete is the cement that holds the construction industry together to rebuild our infrastructure for a better tomorrow.
Everyone knows this, but we all forget and often use the two terms interchangeably – right, I’m referring to concrete and cement. According to the dictionary, and you’ve probably heard or read this a million times or more, concrete is “an artificial, stone-like material used for various structural purposes, made by mixing cement and various aggregates, as sand, pebbles, gravel or shale, with water and allowing the mixture to harden.” On the other hand, cement is “any of various calcined mixtures of clay and limestone, usually mixed with water and sand, gravel, etc., to form concrete that are used as a building material.”
Cement and concrete are not the same thing. One is a component of the other; without the one the other cannot exist …
Without concrete the construction industry would be in serious trouble, to say the least. Concrete has been around for a long time. According to the Historical Timeline of Concrete assembled by Auburn University, somewhere around 12,000,000 B.C. (and please, no smart aleck wisecracks about my having been there), “Reactions between limestone and oil shale during spontaneous combustion occurred in Israel to form a natural deposit of cement compounds.”
Around 3,000 B.C. the Egyptians used mud mixed with straw to bind dried bricks and furthered the discovery of lime and gypsum mortar as a binding agent for building the Pyramids. In China, cementitious materials were used to hold bamboo together in their boats and in the construction of the Great Wall. Around 300 B.C., the Romans incorporated slaked lime – “a volcanic ash called pozzuolana, found near Pozzuoli by the bay of Naples. They used lime as a cementitious material. Pliny reported a mortar mixture of 1 part lime to 4 parts sand. Vitruvius reported a 2 parts pozzolana to 1 part lime. Animal fat, milk and blood were used as admixtures.”
Auburn’s Historical Timeline of Concrete runs from 12,000,000 B.C. through 1996 yet has a significant time gap between 400 A.D. and 1678. After the collapse of the Roman Empire, people stopped using concrete until 1756, when a British engineer, John Smeaton, rediscovered it. It didn’t gain popular use for some time.
In 1824 Joseph Aspdin of Leeds, England, patented portland cement because it resembled stone quarried on the Island of Portland off the British coast. In 1825 the Erie Canal was the first U.S. project that created serious demand for cement. As new applications developed, the use of cement continued to increase. The first portland cement plant in the U.S. became operational in 1871 in Colplay, Pa.
Since then the importance of cement has continued to increase. Right after the turn of the last century, 1902, Thomas Edison became involved in developing improvements in the rotary kiln, which improved cement production. In the 1930s he became one of the first “contractors” to use concrete to build single-family concrete houses in New Jersey in an effort to provide low-cost housing. Some of them are still standing.
Among his other accomplishments, Edison owned the Thomas A. Edison Cement Works and supplied 160,000 bags of portland cement for the construction of Yankee Stadium in the 1920s. Frank Lloyd Wright designed and built concrete structures as well as concrete furniture. Both of these men were major contributors to the use of concrete in construction.
Today there are endless examples of concrete construction applications, but two that readily serve as monuments to the value of this material to society are Hoover Dam and Coulee Dam, both built in the late ’30s (circa 1936) with literally millions of cubic yards of concrete (Hoover Dam – 4,360,000 cubic yards; Grand Coulee – 11,975,520 cubic yards).
Through the years industry has consumed an immeasurable amount of the earth’s basic natural resources in making portland cement – for example, limestone, shale and silica sand are the raw manufacturing materials, and coal and oil fuel the heat needed to fuse these materials. More recently, shredded tires have also been used in the manufacturing of portland cement. Along with the consumption of these materials, the final product of cement – concrete – uses reinforcing and prestressing steels, aggregates, admixtures and more recently, supplementary cementing materials like fly ash, slag, pozzolans and silica fume. The list of these consumable materials goes on as the industry and producers continue to look for ways to not only improve the product but also make it “green.”
Concrete is a critical component in our quest to improve the infrastructure of the world in which we live. As the industry continues to improve the product, contractors and equipment manufacturers continue to find new and better ways to apply it, and architects, engineers and designers continue to find new ways to use it.
No question, there are negatives to using cement to produce the concrete products that make our lives more comfortable, but the industry continues to evolve, and as part of the evolutionary process becomes more environmentally friendly. When you look at the Pyramids, the Great Wall, Hoover Dam, Grand Coulee Dam or Yankee stadium, you can see how cement and its products have played a critical role in the advancement of mankind and civilization. The next time you pull into a parking deck, cross over a bridge, or enter a hospital, stadium or office building, notice the materials that made it possible.
In this issue we are looking at the role concrete plays in construction, its applications and how it’s put in place. If you are interested in reading articles appearing in the other ACP magazines, visit www.site-kconstructionzone.com.
Editor’s note: Click here to see Auburn University’s Historical Timeline of Concrete.
This article appeared in the ACP magazines as the October 2009 editorial.