Concrete

Concrete was a building material created by the addition of gravel to cement. (TV: Destiny of the Daleks) It was a material that hardened over time. (TV: The Twin Dilemma)

Reinforced concrete was a strong building material which was difficult to break through. (TV: Genesis of the Daleks, The Brain of Morbius) On Inferno Earth, ferrous concrete was also strong when combined with steel plating and asbestos sheeting. (TV: Inferno)

History

Concrete was invented by the Roman Empire, (COMIC: Quite Interesting) though Ace McShane noted that "they didn't have concrete" in the 8th century. (TV: Battlefield)

The Fourth Doctor called concrete an indicator of civilisation on the mysterious planet on which they'd landed. (TV: Destiny of the Daleks)

When Tom Mordley was buried in a golden coffin, it was sealed with concrete. (PROSE: Silver-Tongued Liars)

A car factory in Arcopolis was made of diamond-reinforced type five space concrete. (PROSE: The Eyeless)