anhydrite

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Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the orthorhombic barium (baryte) and strontium (celestine) sulfates, as might be expected from the chemical formulas. Distinctly developed crystals are somewhat rare, the mineral usually presenting the form of cleavage masses. The Mohs hardness is 3.5, and the specific gravity is 2.9. The color is white, sometimes greyish, bluish, or purple. On the best developed of the three cleavages, the lustre is pearly; on other surfaces it is glassy. When exposed to water, anhydrite readily transforms to the more commonly occurring gypsum, (CaSO4·2H2O) by the absorption of water. This transformation is reversible, with gypsum or calcium sulfate hemihydrate forming anhydrite by heating to around 200 °C (400 °F) under normal atmospheric conditions. Anhydrite is commonly associated with calcite, halite, and sulfides such as galena, chalcopyrite, molybdenite, and pyrite in vein deposits.

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  1. AD Ceramics

    anhydrite

    Hi Guys Just had the rep from Mapei out today to spec for 60m² 800x800 tiling to a kitchen on to anhydrite screed, never tiled on to an anhydrite screed always steered clear of them, what would you use to sand the floor for the best results? he specified Mapei primer T after sanding as many...
  2. I

    Failed anhydrite floor

    I went to look at a floor that had failed a couple of days ago and of the 60 m2, not much of it seems to be left attached to the screed. The grout is cracking and most tiles sound hollow. It's going to be a mammoth task sorting it out as the skirtings and kitchen are all fitted ontop. Now before...
    • Ian
    • Thread
    • adhesive anhydrite anhydrite adhesive aus floor floor tiling screed usa
    • Replies: 75
    • Forum: Canada Tile Advice
  3. I

    SLC on anhydrite

    Has anyone successfully done this? And are there any gypsum based SLC's out there? I've done somewhere in the region of 500 m2 on these screeds now and not one of them has been decent, it's always around the edges where it's run away (poor prep!), always end up building up the adhesive in...
    • Ian
    • Thread
    • adhesive anhydrite aus screed slc usa
    • Replies: 13
    • Forum: Canada Tile Advice
  4. Dave

    Anhydrite Screeds: Are You Confident When Tiling To Them?

    As the market is growing very fast for Anhydrite screeds , are you as a tiler ok tiling to them and are you confident in doing so.
    • Dave
    • Thread
    • adhesive anhydrite anhydrite adhesive aus screed tiling usa
    • Replies: 66
    • Forum: Canada Tile Advice
  5. J

    Priming Anhydrite Screed

    Anhydrite screed on kitchen floor with UFH. There were some hairline cracks which were bonded with Flowcrete PHS. Floor is otherwise sound and dry and has been sanded. Plan is to use porcelain tiles on Ditra mat. May also have to apply some levelling compound but only to small areas...
    • jesteh
    • Thread
    • adhesive anhydrite anhydrite adhesive aus priming screed usa
    • Replies: 7
    • Forum: Canada Tile Advice
  6. D

    Anhydrite friendly adhesives.

    Are we being over charged for Gypsum based/friendly adhesives..? Are we being taken for mugs because they think they have found the magic cure for tiling to Anhydrite screeds etc..?
    • DHTiling
    • Thread
    • adhesive adhesives anhydrite aus screed tile adhesive usa
    • Replies: 26
    • Forum: Canada Tile Advice
  7. H

    Norcross anhydrite floor adhesive

    Hi, has anybody used this adhesive if so is it any good. Got 60m2 of stone put down and also does this adhesive require the anhydrite screed to be sealed ? cheers Steve
    • Higgzzee
    • Thread
    • adhesive anhydrite anhydrite adhesive aus floor floor tiling screed tile adhesive usa
    • Replies: 11
    • Forum: Canada Tile Advice
  8. S

    Travertine on Anhydrite screed

    Having read many posts on anhydrite screed I am totally confused. We have a 5x6m screed floor to tille with travertine. The travertine is unfilled with minimal holes 12mm thick and various sizes (opus pattern). The screed is 55mm thick and has been down for 90 days now. It has been heated...
    • smallholder
    • Thread
    • adhesive anhydrite aus screed travertine usa
    • Replies: 7
    • Forum: Canada Tile Advice
  9. G

    Ditra on Anhydrite

    So if you were using the Ditra over Anhydrite/Gyvlon type screeds what adhesive would you be using to fix the mat down with ?
    • Gazzer
    • Thread
    • adhesive anhydrite anhydrite adhesive anti-crack aus ditra floor matting membrane schluter screed systems uncoupling usa
    • Replies: 137
    • Forum: Canada Tile Advice
  10. D

    Anhydrite screed prep and moisture testing

    I have an anhydrite screed which I have been testing with a digital hygrometer which measure relative humidity. After further research there seems to be conflicting views on how to test if they are dry enough. I was waiting until it read less than 75% RH. Then I was going to proceed with an...
    • Deleted member 18697
    • Thread
    • adhesive anhydrite aus moisture prep screed testing usa
    • Replies: 1
    • Forum: UK Tiling Forum
  11. B

    Anhydrite moisture testing, putting some ideas to you Trusted People

    Hiya me again, and guess what it's Anydrite again, but i'm hoping something positive. As we all know i've been asking lots of people lots of questions on all aspects of this flooring to try and get some kinda satisfactory answers and systems in place for us all. Now, a question to you all, be...
    • bugs183
    • Thread
    • adhesive anhydrite aus ideas moisture people screed testing trusted usa
    • Replies: 58
    • Forum: UK Tiling Forum
  12. B

    Anhydrite adhesive test.

    Hiya fellas. I've been on a large anhydrite floor and thought i'd do a little test whilst i was there. It is by no means scientific and was done quickly, but this does copy conditions found on site and not in a lab. The floor has underfloor heating, has been carbide bomb tested and was dry, and...
    • bugs183
    • Thread
    • adhesive anhydrite anhydrite adhesive aus screed test tile adhesive usa
    • Replies: 60
    • Forum: UK Tiling Forum
  13. E

    anhydrite floor screeds

    Hi All, Ive been hearing on the grape vine that there is a lot of confusion around tiling on anhydrite floor screeds, if you have a question regarding any issues with a screed you may have please feel free to ask, we can give advise on all aspects. Express screed lay various types of screeds...
    • expressscreed
    • Thread
    • adhesive anhydrite aus floor floor tiling screed usa
    • Replies: 2
    • Forum: UK Tiling Forum
  14. F

    Anhydrite screed diy tiling advice Photos included

    Hi there this is my first post from me. I have been renovating my house for the last 2+ years, it is a early 18th century cottage style house set quite rural. Around 19 months ago i set about installing under floor heating (wet system) did all the prep work myself. It already had a...
    • F430
    • Thread
    • adhesive advice anhydrite aus bathroom diy do it yourself floor kitchen screed tiling usa walls and floor
    • Replies: 5
    • Forum: UK Tiling Forum
  15. T

    anhydrite screed

    hi all,i am tiling 60x60 porcelain tiles onto anhydrite piped underfloor heated floor,it has been laid for over three years,does the floor need sanding first to take primer?thank's tysontile:yikes:
    • tysontile
    • Thread
    • adhesive anhydrite aus screed usa
    • Replies: 2
    • Forum: UK Tiling Forum
  16. R

    Gyvlon/Anhydrite

    There's lots of info here on preparing these screeds for tiling. Sooner or later though, we'll come across one in a re-tile situation. Will it be obvious that its an anhydrite screed and will there be any extra prep other than hoovering and priming?
    • Rookery
    • Thread
    • adhesive anhydrite aus screed usa
    • Replies: 10
    • Forum: UK Tiling Forum
  17. R

    Gyvlon and anhydrite

    I have tiled anhydrite screed floors but reading a lot about gyvlon screed. what is a difference? Which one is better? Are the prep works, sanding,priming the same? thanks
  18. T

    tile over anhydrite screeds

    Hi Looking for a bit of advice, I have been ask to tile a kitchen and shower room floor in a new build by a contractor. Just found out today it has a anhydrite screed on the down stair floor. I have looked on the net for information and it said that it has to be mechanically abraded and an...
    • toshtiles11771
    • Thread
    • adhesive anhydrite anhydrite adhesive aus over screed tile usa
    • Replies: 10
    • Forum: UK Tiling Forum
  19. K

    Tile on anhydrite

    Hi all, I'm new to this so please bear with me. I have a problem with my floor tiles that had been laid on to an anhydrite screed. Floor was apparently prepared as per instructions but a few months ago I noticed white powdery substance coming up through grout. I will try and attach 2 photos...
    • kiero
    • Thread
    • adhesive anhydrite aus screed tile usa
    • Replies: 10
    • Forum: UK Tiling Forum
  20. C

    Weber PR360 preparing anhydrite ,right or wrong

    Hi all Ok went for weber plus adhesive with Ad250 I have prepared the floors and started with the primer Weber Pr360. I understood that one 5 kg container would do approx 25 sq m at 0.2kg per sq metre however i am still on my first container having done over 100 sq m. It says for Anhydrate to...
    • chequers
    • Thread
    • adhesive anhydrite aus preparing screed usa weber weber adhesive
    • Replies: 2
    • Forum: UK Tiling Forum
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