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Discussion Starter · #1 ·
Kind of frustrating, I used the expanding foam and covered with tile grout. I spent hours painting my rocks now the grout is starting to crack. I used about 4 or 5 thick layers of grout, but still cracking. The weather is starting to change, so I'm guessing the foam is expanding and contracting? Anyone else had this problem? Any way around it? Thanks!
 

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Yeah I'm having that problem. I think I started covering it too soon before it "settled" completely. I'm going to continue spraying the grout as it cures for a week or so then fill in the cracks with more grout and see how that holds up.
 

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this is a classic mistake....

grout/cement/etc takes a long time to fully cure.

-how long did you wait between coats? I would recommend waiting a minimum of 3 days between each coat at a minimum

-how did you cure it? how long did you cure it for?

-did you mist it/ keep it moist regularly while curing?
 

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this is a classic mistake....

grout/cement/etc takes a long time to fully cure.

-how long did you wait between coats? I would recommend waiting a minimum of 3 days between each coat at a minimum

-how did you cure it? how long did you cure it for?

-did you mist it/ keep it moist regularly while curing?
I waited 2 to 3 days usually, I'm still curing it by spraying it down multiple times a day.
 

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How thin are you making your grout? Remember that as the water leaves the matrix, there is now a void where the water particles used to be. That void is filled with air instead and results in a much weaker material. So the more water you use, the thinner and more paint-like the material, but the more likely it is to crack.

Thing to keep in mind with all our grout designs aside from the major pH issue, is cement/grout/plasters are all very brittle. They only gain strength from aggregate, support beams, and volume. We use none of this and usually over-water the material too. So the fact that it is cracking on you is because of one of the above reasons AND because you are using grout. Just comes with the territory with using these material this way.
 
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