ROMAN CONCRETE: THE ASCENT, SUMMIT, AND DECLINE OF AN ART

Th e evidence of the surviving literature and structure provides this chronology for the development of concrete: Fronto dates for us, by naming consuls, two aqueducts utterly devoid of concrete at 312 and 272 B.C. From Cato, who died in 149 B.C., we can discern that (a) concrete has now become the normal foundation for building, (b) limeburning is now an established trade, and (c) his recipe for cement is primi-tive—even medieval—and non-hydraulic. Th e year 140 saw the opening of the Marcian Aqueduct, its water-channel lined in non-hydraulic cement. Vitruvius, ca. 25 B.C., describes diff erent cement formulations for diff erent purposes, even giving, knowingly, a recipe for hydraulic cement. Th e years 38–52, nonetheless, included the building of two aqueducts in the non-hydraulic variety. Th e harbor at Ostia, built with hydraulic concrete, is fi nished by 62 A.D. In this same pe