oridginally posted byThe Almond
Ok, then after you add water, allow the concrete to stiffen, then remix it. You should get a higher slump for the material after you remix.
I would suggest finding a hydrated source of gypsum, if you're going to simulate those conditions. I think Plaster of Paris is actually hydrated gypsum
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Hydrated Anhydrite is gypsum.
Plaster of Paris is cooked Gypsum after it is heated to 350c.
Plaster of Paris is Anhydrite, acids increase the Hydrating ability and the ability to retain more acid, especially sulfuric acid.
False set is something well known by the industry, and they certainly wouldn't have allowed it to happen during the construction of the WTC towers.
Yes but they were experimenting with using Gypsum in concrete for fire resistance. Were not even talking about the set here we are talking about fire resistance. The Gypsum used in fire resistance concrete is Hydrated gypsum it is not used for the same purpose as setting.
Dr. Greening is correct that gypsum is added to clinker to form cement. The amount of gypsum added depends on the amount of C3A in the clinker. If you add too little gypsum, you get flash set when the C3A hydrates to form monosulfoaluminate and hydrogarnet. If you add too much, you get a host of other problems like delayed ettringite formation, and weakened cement paste.
Your confusing Anhydrate, plaster of paris, Calcium + Sulfate, with gypsum, Calcium+Sulfate+H20.
Limestone is primarily composed of calcite and dolemite (CaCO3 and Mg*CaCO3), so I don't know how gypsum would form. You can calcine the limestone by heating calcite. That reaction is:
CaCO3 + Heat ---> Ca(OH)2 + CO2
Yes the quick lime process, at 600c thought of that.
But sulfuric acid breaks the Co3 bond releasing carbon dioxide and carbon monoxide.
That leaves Calcium Sulfate it absorbs H20 and Sulfuric acid from the air as it forms Gypsum.
From that, you can sulfonate the mixture by applying acid washes, but the end result is that you can't necessarily spontaneously create gypsum in concrete. Calcination occurs at about 800 degrees centigrade, and ettringite breaks down to monosulfoaluminate far before that happens.
I can desolve lime stone in battery acid, sulfuric acid I do it all the time always froms gypsum hydrated calcium sulfate.
HCl in toilet bowl cleaner will do it forming calcium chloride.
These are very simple known chemical reactions HCL is formed by sulfate attack on limestone in concrete releasing Sodium Chloride + Sulfuric Acid creates sodium sulfate, and HCl that reacts with Calcium carbonate to form Calcium Chloride. Calcium Chloride leaching from the concrete was believed to cause the rusting problem at the world trade center.
As for your hypothesis, my fire protection class mentioned nothing of such a reaction. I also haven't seen anything like this in the literature. Of course, that does not rule out the possibility that sulfuric acid is released when concrete is heated, but I just don't know what the effects would be.
If it had been known I could have looked it up on the internet, insteed of looking for it for the past 6 or so years.
Remember that concrete has a pH of about 10.5, and that, while ettringite will break down at anything below 10, CSH gel is quite hardy, and will remain stable below a pH of 7. If you think sulfuric acid is the culprit, you're going to have to account for huge volumes of material.
Thousands of gallons of diesel fuel continually refreashed, sulfuric acid batteries, and others sources do that. The Gypsum formed by the reaction of sulfuric acid with Calcium Carbonate is stable and locks further acid in harmless suspention between the gypsum Crystals with H20, until released by heating to 350c.
I'll be interested to see what you come up with.[/QUOTE]
I wish I had some one to help me film it, it is just an unknown reaction, of common materials.
Gun cotton drywall the material also has to be in a place where the hydrogen will collect like in a building designed to stop chimney effects from traveling up elevator shafts.
I have been using an old home made barbecue grill to test samples I sealed the grill with clay and then use charcoal to heat the samples, when the hydrogen ignites the top of the grill is thrown open. I can used the weight of the grills top to determine how big the reaction was.
I can also add extra weights on top to see how much more hydrogen can be produced. Since the hydrogen rises
it is trapped in the top sealed by the clay.
I did a big sample earlier now I am doing smaller samples to give me some ball park figures as to strength of the reaction.
If this fails I am finally going out and buy one of those boxes that you guys have to think in.
because of all the cleaning up I have to do.