Concrete – How long will stored powder charges last

According to the Copper Development Association, it is perfectly fine to embed copper tube in concrete under certain conditions. However, it is unlikely your home met all the conditions like making provision for thermal expansion (especially important with a heating system that will likely cycle on and off many times in one day) Another important requirement is to protect the copper if "it comes in contact with concrete mixtures that contain components high in sulfur, such as cinders and fly-ash, which can create an acid that is highly corrosive to most metals including copper."

In the early 80s I lived in a house that had plumbing in the concrete slab floor. Not heat, just domestic water. It was much younger at the time than your house is now. There was a leak and the only way to find and fix it was to jack-hammer the living room floor. Because the water followed existing cracks in the concrete, a lot of concrete had to be removed to find the actual location of the leak.

My recommendation: write off the radiant heat system and budget for a forced air heat replacement. You can upgrade the house to have air conditioning for the summer at the same time.

Concrete will definitely be strong enough if done right.

Make sure you use the right mix. I would use sakrete 5000 plus, NOT quikcrete 5000, and add a hand full of Portland cement to better hold the mosaic. Then add superplasticizers. More water is bad, but you want it to flow into an odd shaped mold and around mosaic tiles, superplasticizers will solve this. You can get this at http://www.expressions-ltd.com/default.asp You can get some integral coloring for the concrete there too.

The forms will be tricky, but i think i would build a wood box and drape some cloth in it the way you want. Then spread some glue on it to stiffen it up. Then use bondo and sand it down to smooth. Then you can use some spray adhesive or silicone to put your mosaic tiles in upside down.

You are going to need to vibrate it after you pour it. Maybe just hammer on the wood box.

I am saying this would be solid concrete, but this will be very heavy when you demold it. You could put something lighter in the mix after you pour it, maybe some empty bottles?

Anyway, yes, this can be done with concrete. Concrete would be very strong, and no you don't need mesh in this setting. The tensile strength of concrete is terrible but the compressive strength is amazing.