updating old red brick fireplace

I tried to 'skim coat' a floor-to-ceiling mid-century fireplace - red brick over concrete block construction. Here's what I tried without success (looked great for a few days then fell off): thinset (acrylic fortified) over the brick, then a finish coat of portland cement steel trowel finish. The finish coat went on after the thinset had fully dried - a few days or so. I wetted the thinset coat well before applying the cement finish coat, however. I fully expected this to work. The 'polido' finish is common: fine cement stucco over concrete block with a final portland cement slurry troweled over to a polished finish. Drying conditions affect adhesion of the polido so I was careful to manage the drying of my fireplace polido accordingly. As it turned out, some sections of the finish adhered perfectly but much of the work is cracking and falling off.
I'd appreciate guidance on how/what I can get to work with the dry thinset coat and why my polido finish is falling off. I'm assuming the acrylic prevented a good bonding with the cement. Not sure why parts of the finish are good and others not. If the acrylic is indeed the problem what should I use as a new intermediate step to bridge to the polido coat? Thinking Sika something.
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Define what you mean by portland cement steel trowel finish, If you literally mean you troweled on a slurry of Portland and water on thinset, I don't see any way it could have worked. If all you wanted was a slick cementitious finish, why didn't you hard trowel the thinset? It would not have been my choice of products to apply to the brick work. The finish coat you applied needed sand and probably some lime to work. Cement alone is NOT a finish.
What do you want to end up with? I imagine it would be major to try to remove the thinset. Can you remove all of your finish coat, back down to the thinset? Is the thinset flat enough to be finished or do you require additional "brown coat" type work? Is there any physical tooth to your thinset coat, typically called a "scratch coat" to provide adhesion of the next coat?
If you have a good plane established that will require no more than an 1/8" for finish and you can get all of your finish off, you may be able to apply EIFS finish coat. Most brands you will not be able to buy, but you should be authorized to purchase Parex, often available at major drywall houses. Here is some info: http://www.parex.com/ click on Systems/EIFS Products/Finishes&Coatings
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By steel trowelled portland cement finish I mean making a paste with portland cement and troweling it over a rough cementitious surface. I work in Mexico where it's common. It works well and looks great. About 1/2 of the coat I put over the the thinset adhered well and looks good. Blind luck I guess. You're right, I should have worked the thinset. Thanks for the lead on parex. In Mexico, concrete block. Then a sand + cement mix then the final 'polido'. Most of the time it bonds well. Depends significantly on the age of the sanded coat - overnight vs over the weekend - and how it dried in the otherwise hot dry climate. Not sure where the limits are on this method. Thoughts?
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