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A concrete explanation

A gentleman named Hugh Andrew has written about a common error that irritates him, and since it irritates me as well, I quote him in full. If you aspire to be known as a careful and precise writer, pay attention.

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.

Technically, Portland cement concrete is not the only kind of concrete. When a stone aggregate is mixed with a bitumen—usually petroleum-based asphalt—the resulting material can be called bituminous concrete. It is much simpler and more descriptive to call this product by its common name. We properly call it blacktop, unless it is a paving material used in an airport, when it mysteriously becomes tarmac. Much of the paved surface at airports these days is concrete and not blacktop. I suspect that news people use the word tarmac to describe all of these air terminal surfaces. At least, they do not call them cement runways!



Posted by John McIntyre at 4:00 PM | | Comments (14)


The term "tarmac" combines "tar" and "macadam" to describe a mixture of broken stone and tar used to surface roads and runways.

In 1901, an Englishman, E. Purnell Hooley, passing a tar works, noticed that a barrel had spilled and that someone had poured gravel on top of the mess. That area of the road seemed free of dust. Hooley then started the Tar Macadam Syndicate Limited.

Eventually, asphalt became available and replaced the use of tar. Traditional tarmac is rare even though the term is used generically to describe runway surfaces at airports.

Do we do macadam next? ;)

My dad, a civil engineer whose career was spent in the construction of large concrete structures, drilled the difference between cement and concrete into my head during the period that "Beverly Hillbillies" ran on television. Every time Granny or Jethro referred to the "ce-ment pond" out back, my Dad would correct them by muttering, under his breath, "Concrete pond..."

(There are four paved surfaces at an airport, by the way: the ramp, the apron, the taxiway and the runway. And I've never heard anyone who actually controls an aircraft substitute "tarmac" for any of them.)

Prof. McIntyre, maybe you could add to your list a topic explaining the difference between a cow, a heifer, a steer and a bull. Those distinctions were to my father-in-law what the cement-concrete distinction was to my dad.)

Mr. Andrew notes a mistake, which has been corrected in the text:

"I have realized that there is a mistake of fact in the e-mail I sent that you posted on your blog relating to cement/concrete. The ultimate strength of concrete is measured in pounds per square INCH, not square foot. An important fact if you are designing a bridge, but it does not change the language issues.

"As the Sun might say under similar circumstances, I regret the error."

I am sure one could find many such misinterpretations and wrongful descriptions. Once such have made it into the popular culture, trying to correct them is futile. The track record is even worse for Brand Names, whose owners must constantly fight to avoid having their trademark become generic, such as Band-Aid™, Jell-O™, or even Fiberglas™.

Bring back glassphalt!

a cement mixer does not make sense.

I disagree. If you put cement in a vessel and mix it with other things, then it is a cement mixer. An egg beater is still an egg beater even if the result is pancake batter or crepe batter.

Is all bold the proper format for Mr. Andrew's letter? It hurts my eyes.

Don't forget about the whole Styrofoam™ issue. From Wikipedia:
The word styrofoam sometimes misused as a generic term for expanded polystyrene foam, such as disposable coffee cups, coolers or packaging material, which are typically white and are made of expanded polystyrene beads. This is different from the extruded polystyrene used for Styrofoam insulation. The polystrene foam used for craft applications, which can be identified by its roughness and by the fact that it "crunches" when cut[5], is not specifically identified as expanded or extruded.

Dow Chemical employs people who do nothing but watch television and scan print media for the improper use of "Styrofoam".

Even weird is that the Oscar Mayer people are also watching for any use of the word "Wienermobile". They show up every time that "Wienermobile" is mentioned on D@L. Yes I know this is the blog equivalent of "made you look", but in these tough economic times we need to keep the wiener watchers employed.

I love glassphalt. Parts of Charles Street used to glitter at night. I heard that they stopped doing it because of a lack of glass. How is that possible? They do glass recycling don't they? I heard that when they lacked enough broken glass that Mayor Schaeffer suggested or possibly had inner city kids throw bottles at walls. Awesome!

Owl, you can still see the occasional glassphalt glimmer on Charles Street near JHU (your old stomping grounds, if we are to believe previous posts).

Maryland Ave. at the intersection with Mt. Royal Ave. is also still paved in glassphalt, as are (or perhaps were, after all this road work) some parts of Charles St. in Mt. Vernon. With its blue and green flecks of glass, it's as pretty as asphalt gets.

Hillen Road in front of Mervo had glassphalt for years, I think its still there.

A high school memory: the day that the English teacher asked a girl in her class to name two kinds of nouns. Answer: "abstract nouns and cement nouns."

"cement" and "concrete" have metaphorical uses as well.

One has concrete plans, and one cements an argument with a final piece of evidence, for example.

In that usage, I think of "cement" as a "hardening glue"--to cement one's plans, one would bind them together and finalize them, in a way that implies a certain amount of unwillingness to change them, and a certain durability of the final product.

"concrete" isn't generally used as a verb, and in my experience implies nothing about a change of state--however, the dictionary (MW11) does not agree w/ me, giving a definition of "to form into a solid mass; combine, blend; to make actual or real"

Do these differences relate at all to the engineering definitions of concrete/cement?

(In fact, my dictionary gives "concrete" as a synonym for "cement."

The other interesting fact about cement is that with hydraulic cements (e.g. the Portland cement you mention) hardens by a chemical reaction with water that occurs separately of the admixture's water content; they can harden even underwater or when constantly exposed to wet weather.

For bovine distinctions, please ask a 4-H member or someone in the Dairy Sciences departments of any good land-grant university. You won't find it here.

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About John McIntyre
John McIntyre, mild-mannered editor for a great metropolitan newspaper, has fussed over writers’ work, to sporadic expressions of gratitude, for thirty years. He is The Sun’s night content production manager and former head of its copy desk. He also teaches editing at Loyola University Maryland. A former president of the American Copy Editors Society, a native of Kentucky, a graduate of Michigan State and Syracuse, and a moderate prescriptivist, he writes about language, journalism, and arbitrarily chosen topics. If you are inspired by a spirit of contradiction, comment on the posts or write to him at
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