Thermal concrete was a material composed mostly of silicon, used by Starfleet in the 23rd century in the construction of emergency shelters.
In 2267, Doctor McCoy used one hundred pounds of thermal concrete to bandage a wound on the silicon-based lifeform known as a "Horta," which appeared to be white-hot where it had been injured. (TOS: "The Devil in the Dark")
In James Blish's novelization of the episode in Star Trek 4, which was generally based moreso on early draft scripts than final drafts, states that McCoy only used ten pounds of concrete.
External link
- Thermal concrete at Memory Beta, the wiki for licensed Star Trek works