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 The Scenic Solution, by Charlotte Overby.

 

When Englishman Joseph Aspdin patented his breakthrough cement mix in 1824, he proudly dubbed it "portland" because the color of the concrete it produced reminded him of beautiful stone quarried on the Isle of Portland, a limestone peninsula in the English Channel.

The new cement had advantages beyond its good looks: it was easier to mix, could harden under water and, most importantly, made for stronger concrete. Still, cynics in the building trades said it didn't have much potential beyond the construction of bridges and dams. Their bearish outlook was due mostly to the arduous, unhealthy process of producing the stuff. Cement manufacture was hard on workers, left great holes in the earth from quarries, and scarred the landscape with heaps of heat-blasted dust left over from the manufacturing process.

The skeptics, of course, were wrong: Portland cement is now the most popular building material in the world. And unlike the anything-goes ethos of the typical 19th century cement entrepreneur, many of today's cement manufacturers are working hard to lessen its environmental impact. Notable among them is the Continental Cement Company, a century-old plant in Hannibal, Mo., that for the past three years has teamed up with a trio of researchers from MU to come up with a scenic solution to dust left over from portland cement making.

"The idea is to make an artificial soil out of various materials, to use it to immobilize a potentially hazardous waste and, over the long term, essentially to recreate a sustainable natural resource to reclaim the land," says William Likos, an assistant professor of civil and environmental engineering at MU who is part of the team working with Continental.

So far their work has changed only a small portion of a single limestone quarry. But the technique they've employed could one day help restore thousands of similarly blighted landscapes.

Cement is an ancient material. The Babylonians made a version from clay. The Egyptians improved on it by using heat-fired lime, gypsum and water to bind sand and pebbles into mortar for the pyramids. The Romans re-added clay to the Egyptian mix, then used it to lay foundations for virtually all of the great structures that came to symbolize their empire.

Joseph Aspdin, a mason and brick layer by trade, made his mark on this distinguished history by "rediscovering" what the Romans knew: that pulverizing a controlled portion of limestone and clay together changed the chemical properties of both. Burned to the point of reforming into a "clinkered" mass, the materials were ground to a powder then blended with gypsum to form a mix that -- when combined with water and aggregate -- made for an amazingly durable concrete. Aspdin jealously guarded the details of his process, even to the point of building 20-foot-high walls around his Wakefield, England, plant. His recipe was copied anyway, and portland cement took its place among the world's most important building materials.

So it remains. According to industry figures, some 98 percent of the world's cement is portland. Here in the United States, there are 178 companies manufacturing portland cement in 279 different locations, with at least one manufacturer located in every state. Together they do $6.5 billion in business each year.

       
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Published by the Office of Research. Copyright 2005, Curators of the University of Missouri. Click here to contact the editor.