In my experience, hypertufa and moisture co-exist beautifully, however, since the 'tufa is porous, you don't want to let your project freeze. Any water that is inside the 'tufa will expand and probably crack the 'tufa.

The problem with hypertufa is that, eventually, the organic matter in the mix will rot out and leave crevices. Water creeps in, freezes, and the piece starts cracking.

Concrete doesn't have organic materials in the mix. If you added an acrylic or vinyl fortifier to concrete, it should help block passage of moisture (concrete isn't totally solid).

Before you invest good money in colors, contact the seller or mfgr and ask if the colors stay clear if or if not they are sealed, OUTDOORS. Some concrete floor contractors have run into a problem with the blues and greens turning dark (mold?) when exposed to moisture (like outdoor patios), even when sealed. If not exposed to excessive moisture, they were fine.

Sie