What is "roman cement"

Roman \Ro"man\, a. [L. Romanus, fr. Roma Rome: cf. F. romain. Cf. Romaic, Romance, Romantic.]

1. Of or pertaining to Rome, or the Roman people; like or characteristic of Rome, the Roman people, or things done by Romans; as, Roman fortitude; a Roman aqueduct; Roman art.

2. Of or pertaining to the Roman Catholic religion; professing that religion.

3. (Print.) (a) Upright; erect; -- said of the letters or kind of type ordinarily used, as distinguished from Italic characters. (b) Expressed in letters, not in figures, as I., IV., i., iv., etc.; -- said of numerals, as distinguished from the Arabic numerals, 1, 4, etc. Roman alum (Chem.), a cubical potassium alum formerly obtained in large quantities from Italian alunite, and highly valued by dyers on account of its freedom from iron. Roman balance, a form of balance nearly resembling the modern steelyard. See the Note under Balance, n.,

   1. Roman candle, a kind of firework (generally held in the hand), characterized by the continued emission of shower of sparks, and the ejection, at intervals, of brilliant balls or stars of fire which are thrown upward as they become ignited.

      Roman Catholic, of, pertaining to, or the religion of that church of which the pope is the spiritual head; as, a Roman Catholic priest; the Roman Catholic Church.

      Roman cement, a cement having the property of hardening under water; a species of hydraulic cement.

      Roman law. See under Law.

      Roman nose, a nose somewhat aquiline.

      Roman ocher, a deep, rich orange color, transparent and durable, used by artists.
      --Ure.

      Roman order (Arch.), the composite order. See Composite, a.,

Roman cement is a substance developed by James Parker in the 1780s, and finally patented in 1796.

The name is misleading as it is nothing like any material used by the Romans, but was a "Natural cement" made by burning septaria - nodules that are found in certain clay deposits, and that contain both clay minerals and calcium carbonate. The burnt nodules were ground to a fine powder. This product, made into a mortar with sand, set in 5–15 minutes. The success of Roman cement led other manufacturers to develop rival products by burning artificial mixtures of clay and chalk.