Roman Concrete 1

THE SECRETS OF ROMAN CONCRETE IMAGINE BUILDING STRUCTURES THAT LAST 2,000 YEARS. HOW DID THEY DO IT? OUTLINE - Introduction Concrete Aqueducts The Secret Roman Recipe Buildings Conclusions TREVI FOUNTAIN CONCRETE AQUEDUCT - 11 Aqueducts – 300 miles 150 – 200 gallons per person per day - Aqua Virgo 19 B.C. (Jesus Christ was not born!) 11 miles from Salone springs - Aqua Claudia - 50 miles – Arcades of arches 60 feet high - · Aqua Alsietina · Aqua Appia · Aqua Augusta (Naples) · Aqua Augusta (Rome) · Aqua Claudia · Aqua Julia · Aqua Marcia · Aqua Martia · Aqua Tepula · Aqua Traiana CONCRETE AQUEDUCT Segovia Aqua Claudia THE SECRET ROMAN RECIPE • Lime-coated mud walls were constructed in central India as early as 2,500 B.C. • Romans, used it as a sort of stucco covering for mud walls and other crude structures • It is not known exactly when the Romans first began mixing lime with other substances to form concrete • a wall of rubble in Pompeii was held together with a firm black pozzolan and lime mortar dating to the late third century before Christ • by 199 B.C. the Romans were already using hydraulic concrete to line the harbor works at Puteoli, which indicates a • striking degree of sophistication. THE SECRET ROMAN RECIPE • Use of Roman concrete reached its zenith during the reigns of the Emperors Trajan and Hadrian, 98 to 138 A.D. • By that time the craftsmen were well trained with many tools and they were sufficiently educated to attain teamwork. • An example of concrete construction from this period is Trajan’s Forum, the forerunner of today’s shopping mall: 150 stores in the middle of old Rome. • The ruins of this landmark can still be observed today, including its centerpiece, the Great Hall, whose vaulted roof is still intact. THE SECRET ROMAN RECIPE THE SECRET ROMAN RECIPE • The Romans had two distinct types of concrete mortar: binder aggregate water 1 part lime 3 parts crushed sand 15-20% 1 part lime 2 parts river sand 15-20% 1 part 2 parts lime river sand plus 1 part of tile fragment 15-20% 1 part lime 15-20% 2 parts pozzolan “DE ARCHITECTVRA” (Vitruvius, II, v, 5) (Vitruvius, II, v, 6) (Vitruvius, II, v, 7) (Vitruvius, v, XII, 8-9) THE SECRET ROMAN RECIPE • Marcus Vitruvius Pollio • Vitruvius an engineer and architect for the Emperor Augustus, wrote 10 books on architecture and engineering: DE ARCHITECTVRA “there is also a kind of powder which from natural causes produces astonishing results. It is found in the neighborhood of Baiae and in the country belonging to the towns round about Mount Vesuvius. This substance, when mixed with lime and rubble, not only lends strength to buildings of other kinds, but even when piers of it are constructed in the sea, they set hard under water.” “Est etiam genus pulveris quod efficit naturaliter res admirandas. nascitur in regionibus Baianis et in agris municipiorum quae sunt circa Vesuvium montem. quod commixtum cum calce et caemento non modo ceteris aedificiis praestat firmitatem, sed etiam moles cum struuntur in mari, sub aqua solidescunt.” THE SECRET ROMAN RECIPE • Pozzolan • A siliceous or aluminous material which in itself possesses no cementitious value, but will, in a finely divided form, and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties • By using volcanic ash in the place of river sand in their concrete, the Romans were able to mimic the process by which Portland cement chemically bonds lime to clay through the application of heat. • But finely divided pozzolan must be amorphous (glassy) to chemically react.