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Saturday aside: it’s concrete, not cement

Construction junkies and engineering types may appreciate this discussion at a language-related blog I read, written by the top copy editor at the Baltimore Sun. An engineer writes in to say he’s absolutely fed up with people who think cement and concrete are the same thing.

One current word usage continues to bother me. It is the use of the word “Cement” when the writer or speaker means “Concrete.” I learned the difference between the two terms more than fifty years ago in the School of Engineering at Johns Hopkins. I know that the language evolves, but this particular evolution tends to be confusing.

Cement or Portland cement, to use the technical name, is a greenish-gray finely ground powder that is one of the ingredients in concrete. The Portland Cement Association, a trade group representing manufacturers of this material, maintains an informative web site at When this manufactured chemical is mixed with gradated aggregates—usually coarse sand and either gravel or crushed stone—and water is added the resulting mixture is concrete. A chemical reaction will then take place that will cause the mixture to harden within a few hours. If the ingredients have been properly proportioned, and if the product has not been subjected to climate extremes, in approximately 28 days, this man-made conglomerate will become strong enough to withstand a compressive force of 3,000 pounds per square inch or more. Concrete is an ideal construction material. Because it is put in place in a semi-liquid state, it can be molded into shapes that are structural or decorative or both.

However, it is concrete, and cement is just one ingredient. Therefore, to speak of a cement sidewalk or a cement mixer does not make sense.

Read the comments to find out where “tarmac” comes from, and why no respectable airport employee ever uses the term.

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Tom Mangan posted at 9:23 am January 3rd, 2009 |

One Response to 'Saturday aside: it’s concrete, not cement'

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  1. Mahkno says:

    Good point… and guilty of it as well.

    Permalink | Posted January 4th, 2009, at 5:16 pm

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