Condensation?

Most likely the slab doesn't have a vapor barrier under it. The dew point would be trapped by anything laying on the slab.

John

In addition, copper reacts with concrete, forming salt crystals that will eventually eat the copper. The salt crystals absorb moisture from the concrete. Look at the copper surface where it touched. Are there small white crystals formations?

John

in refrigeration the exposed ducts of copper to environment are had with a layer of rubber of 2 " with thickness, to avoid the condensation, your these exactly doing?

copper is a very good heat conductor. The layer in contact with the cement is cooled by the earth and this draws more heat from the bulk of copper and the air. A thin layer of water on the cement accelerates the problem as it increases the contact area.

This cooling will cause condensation on the copper. Test this by suspending the coil 1/4" above the cement with rope or a closed cell foam pad. Once contact is broken, the problem will cease

This is the same thing that causes condensation on engines etc left on conctrete floors (or any any metal object)

"Say I have 50' of insulated coppers wire coiled up and layingon a concrete floor(not live)."

Didn't anyone read the OP insulated, INSULATED, INSULATED !

Since the copper can not react chemically with the concrete it will still cool off at night and the vapor from the warm concrete will collect on and under the cooler wire in the morning.