cement?

Clearly, I was asking the wrong question when I queried what concrete is, because from your descriptions, it's just cement with some rocks
(sand/gravel) thrown in for good measure. I guess the real question I should have asked was: what is cement, and more specifically how it's formulation has changed over the millenia. Clearly lime is involved, but agricultural lime (Calcium Carbonate) is pretty darn unreactive, so there must be a more reactive form of lime (quick lime?) which is involved. The next question is how exactly this lime reacts with the material it's put with to create something hard and durable. I hope this doesn't turn into a chemistry question, but materials science is certainly based in part on the chemical properties of the materials we use. Anyway, if anyone has useful information on cement, I'd love to hear it. Thanks. Bruce
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If you are speaking of millenia, there are tens (hundreds?) of possible formulations of "cement" which were used since the "beginnings". Just look at puzzolane. Non long ago, dentist cements were even based on Zn phosphate or silicate. J.J.
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Why don't you look up the manufacturing process. Solid state reactions take place that turn the raw materials into OPC.
--
Terry Harper
http://www.terry.harper.btinternet.co.uk /
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Terry, Thanks for your suggestion. When I tried to use Google to search for the composition of cement or concrete, I just got companies that sell the stuff. But putting "cement manufacturing process" into Google did the trick. One site I found that had useful information was: http://www.lafarge.com/cgi-bin/lafcom/jsp/content.do?function _process&lang=en
Here's some of what they say on the site: Cement is a hydraulic binder. That means it is a material which sets and hardens when mixed with water. Cement is primarily made up of limestone and clay. It is the result of chemical processing at very high temperatures, after several burning and grinding operations. The raw materials which go into the production of cement, primarily limestone and shale, are extracted from the quarry by blasting. They are then crushed and transported to the plant, where they are stored and homogenized. Very fine grinding provides a fine powder known as raw meal, which is then pre-heated and then enters the kiln. Flames reaching temperatures of 2000C heat the material to 1500C, before drastically cooling it by air blasts. The burning process produces cement clinker, the basic material required for the production of all cement. Clinker and gypsum are finely ground together to obtain a "pure cement". Secondary constituents are also added to make blended cements. Lastly, the finished products are stored in large silos from where they are dispatched in bulk or in bags to where they will be used.
On Tue, 16 Sep 2003 19:43:04 +0000 (UTC), "Terry Harper"

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