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Tom Mazanec
Joined: 11 Feb 2016
Posts: 139
Location: Twinsburg, Ohio
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Posted: Jan 29, 2018 10:29 Post subject: Concrete as a mineral |
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Suppose you analyzed a chunk of concrete as if it were a rock. What mineral would you identify it as? |
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Bob Harman
Joined: 06 Nov 2015
Posts: 765
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Posted: Jan 29, 2018 11:32 Post subject: Re: Concrete as a mineral |
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TOM, You probably will get a whole lot more info just googling "concrete" and reading thru several of the explanatory websites.
Basically, concrete is a mixture of small and slightly larger particles of lime based stone and water. It is a slurry when made and, thru a chemical reaction, hardens to the stone phase over several days. Concrete can also be made with an aluminate base mixed with water. Asphalt concrete, used for road surfaces adds bitumen to the mixture. BOB |
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lluis
Joined: 17 Nov 2006
Posts: 712
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Posted: Jan 29, 2018 12:18 Post subject: Re: Concrete as a mineral |
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Hi, Bob
The chemistry of cement is far more complicated that the one you said, The stones added inside, I thought for what I saw in Catalonia, and for what was said me in my career in Chemistry, that were mainly quartz.
Besides, as an important point, using aluminum compounds in cement leads to "aluminosis"
This type of concrete degrades very quickly with humidity...
You see, not a simple thing. Inside you would find calcium carbonate, and many phases of calcium and sodium silicates.
And if you go to old roman cements, even odder things, that, besides, make the compound even more resistant... (I think an article was posted here....)
With best wishes
Lluís |
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Dale Hallmark
Joined: 16 Jun 2014
Posts: 189
Location: Texas Panhandle
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Posted: Jan 29, 2018 14:26 Post subject: Re: Concrete as a mineral |
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I believe that is a Alkali-Aggregate Reaction (AAR).
Depending on the type of aggregate there are other reactions that can occur,
In siliceous aggregates, the reactions are called "alklali silica reactivity" (ASR).
In dolomitic carbonate rocks, the reactions are called "alkali-carbonate reactivity" (ACR).
When these types of reactions occur, they create a gel-like substance that swells when exposed to moisture and may crack the concrete.
Concrete is a very complicated subject.
Dale |
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Jim Robison
Joined: 17 Nov 2010
Posts: 55
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Posted: Jan 29, 2018 16:43 Post subject: Re: Concrete as a mineral |
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A mineral has a specific chemical formula and composition. While concrete is an aggregate of several types of rocks and processed lime, with water, it is rock like in character. Generally speaking, a rock is a naturally formed aggregate of minerals. Concrete, by this definition, would not be a rock because it is the product of human hands.
As noted above, composition is widely and wildly varied, with certain restraints having to do with the ratio and sizes of the sand, gravel (commonly called aggregate because its components vary in size), cement, water (and often chemical additives). Typically there are types of concrete, as noted above, but there can be considerable variation in the composition of all the components, with the most closely defined being the cement, which is a component of calcined (roasted) lime, and other minerals and chemical additives. Even there', cement comes in several types.
Note in closing that quality control of the ratio's and types of materials that are roasted to make cement are strictly controlled, and from the standpoint of composition, cement is much more rigidly defined.
Fascinating subject, studied closely early in my career when I was using concrete a lot.
The science of cement types has seen major advances since those days many decades ago. I 'd have to almost start over if I was dealing with concrete these days. |
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Pete Modreski
Site Admin
Joined: 30 Jul 2007
Posts: 709
Location: Denver, Colorado
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Posted: Jan 29, 2018 17:57 Post subject: Re: Concrete as a mineral |
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Yes, Tom, as has been said, it's a very complicated subject.
One can, indeed, discuss concrete as "a rock", but the part of your question, "what mineral would it be", isn't exactly a valid question, as, being a mixture of things (like most rocks), it is not any single mineral. And, in the sense that we use "mineral" in mineralogy, only naturally occurring compounds are considered minerals--hence, the inorganic chemical compounds present in cement have formed artificially, not naturally, so we don't class them as "minerals".
And as the others have said here, aside from the pebbles or chips of rock that constitute the "aggregate" in concrete, plus the sand that goes into it, the matrix is made of a complex, fine-grained, poorly crystalline mixture of compounds, most of which never occur in nature. The compounds are basically calcium silicates and calcium aluminum silicates. One of them has a name, "alite", that is used in the technical literature of the cement industry, but it is not considered a true mineral name, because it occurs artificially in cement, not in nature.
As has been said, you can look all this up in great detail, online!
Best regards, Pete |
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Peter Lemkin
Joined: 18 Nov 2016
Posts: 398
Location: Prague
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Posted: Jan 30, 2018 00:19 Post subject: Re: Concrete as a mineral |
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Being a man-made product, it is not a mineral even if its constituents are or are primarily. |
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