I have, on the very first block I poured into my metal block slip forms. It had set for weeks or maybe even months before I got around to adding cement to it, the smell was very bad but I went a head and poured it anyway hoping it would work because if it didn't work, being the first block on the bottom row I would have been in trouble with all the othe blocks and rows above. As it turned out it was the very best block of the whole batch, I still don't know why.
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