Walls – How to repair aerated autoclaved concrete

Mold needs three (or really four) things to grow: Stagnant air, moisture/humidity, and dim or dark areas with organic 'food'. The solution you're looking for probably involves using a permanent waterproof barrier (either a paint product -- which would be an industrial coating -- or a foundation product) in order to largely remove the humidity from the equation. Those coatings would need to be installed by a professional. As a cheaper and DIY solution, you might also consider 6mil plastic vapor barrier on the back side of the wallboard.

If you resurface concrete the cracks from the original concrete will eventually come out to your new surface (Even with the fiber in it, infact thats the only type of concrete we place). Its really better to remove the old concrete and pour in a new porch but that's not really the cost effective way to do it. But if you do decide to resurface it any part of your walls and pillars you want to cover with plastic, and tape down the ends, its very tough to get concrete off of brick and almost impossible to remove it from wood.

But what would be nice if you could do it would be a colored stamped overlay. That way after it is stamped any cracks that might come out wont be noticeable. To do this you need a stampable overlay mix, concrete die, release (I like powdered release over liquid), you can rent the stamps, and a gauge rake to spread it out. Stamping concrete is a little difficult especially with an overlay, the concrete has to be just right (not too wet but not too dry) for the stamp to come out correctly.