If it is galvanized or copper, some felt that coating the metal pipe with driveway sealer or a tar minimized corrosion or electrolysis with the concrete. Another though is if Texas like Florida may have termite protection layer sprayed down before the concrete is poured. Perhaps at the time and available treatment chemicals, this was a way to provide a barrier from termites working up into the home around the pipes. In 2009 while our church was being built in Wellington Florida, the electrician coated all metal conduit elbows that came up from under the slab through the concrete. I asked and he stated to prevent corrosion.
