CONSTRUCTOR/September 200213 - PDF document

CONSTRUCTOR/September 200213 N those catchy, uplifting, end-of-theÒRoman Holiday,Ówith Audrey Hepbaw30 years. But no matter:w comes theawy,VAwhich devoted considerable attention andThe most stunning footage of all wRome, reaching into the foothills of theground. ÒBut ev, mountainsevpossible, given the limitations of ancientThe engineering and construction w T HE S ECRETSOF R OMAN C ONCRETEIMAGINEBUILDINGSTRUCTURESTHATLAST 2,000 YEARS . HOWDIDTHEYDOIT ? The Colosseum, or Flavian Amphitheater, sitsnear the southeast end of the Forum, betweenthe Palatine and Esquiline hills of Rome.Begun by the Emperor Vespasian in circa 75A.D., and completed by his son Titus in 80A.D., it is the most imposing of Roman antiq-uities. The vast, four-storied oval is 617 feetby 512 feet, much of which is still standing.Lost to the ages are tier on tier of marble seatsthat originally accommodated some 45,000spectators, but were looted by succeedinggenerations. The Colosseum encloses anarena measuring 250 feet by 151 feet, thesite of gladiatorial combats until 404 A.D.The structure has been damaged severaltimes by earthquakes and fire, but those por-tions built with Roman concrete endure.Ñ Stephani Miller As to construction contracts, saysMoore, the Romans employed highly Photo by Lakisha Campbell The aqueducts, I knew, were just one eple of Roman concrete. In World War II, U.S.Army Gen. George S. Patton, a celebratedmystic who believed himself to be a reincar-nated ancient w, took great satisfaction indirecting the Seventh and later the Third armyover bridges used by Julius Caesar, Sulla,y, and other Roman commanders. ranean basin, northward to Britain andwly inspired, I hopped on my computer,logged onto Amazon.com, and typed thewords ÒRoman ConcreteÓ into the searchengine. Somebody, surely, the scientistsÑy must have figured it all out long ago. Butnothing came up. Next I logged ontoYahoo.com, typed the same words into the, and bingo:88,000 references. Mostof what I found, ho, was either sky,boilerplate, repetitive, or anecdotal. Certainlythere were some tantalizing snippets, univsity postings in particular, but nothing com-ve, not one discrete publicationwholly devoted to Roman concrete. I didunearth one shiny nugget, hointriguing website, which in turn touted a book, The Roman PtheonÑThe Triumph of Concr, written byvid Moore, P.E. itely footnoted, comprises the defstudy of Roman concreteÑwho, where,ivs in Laurion and Their Speciala scientific and historical perspective onger stonesÑsee sidebar above, right)the elements calcium, carbon, and oxygen. bling, heat-producing chemical reaction, concerning the Roman placement ofhydraulic pressures. Speaking of cis-evbrick, marble, or charcoal as well. zens, soldiers from the Legions, andskilled laborÑguild personsÑMooreskilled labor needed to fasten timbervided the metal work and otherThe guilds were not collective barging devices but almost akin to distinctsocial classes much like the caste systemof India. Once born into a guild, youed up the trade and practiced itthroughout your lifetime. Guilds had theirown meeting halls and even their own god-dess, MinervaÑthe deity of handiwNuma, the early second Roman king, orga-nized the following guilds: flute-players,goldsmiths, dryers, cobblers, tanners, copperers, potters, and carpenters. Other knoguilds included metal wers, for bothbronze and iron; brick and cement masons;timber wers; wagoners; and wreckge16) S E C R E T S S E C R E T SS E C R E T S cium in the lime, ho, does notIt is not known exactly when the Romansfirst began mixing lime with other substancesto form concrete, but Òarcheological studiesve noted that a wall of rubble in Pompeiiwas held together with a firm black and lime mortar dating to the late third centurybefore Christ,Ónotes Moore, citing archeolo-gist M.E. Blake. It is also known from ancientwritings that by 199 B.C. the Romans werealready using hconcrete to line theharbor works at Puteoli, which indicates astriking degree of sophistication. the pozzolanic mortar. Pozzolan.Ónoes, including the most famous of all,ws: A siliceous or aluminous materialh in itself possesses no cementitiousa-tious prTranslated: By usingicial pozzolans, such as fly ashÑacompacted concrete (RCC),a stiff, zero-slump concrete. The cementitious binderdecrease concrete porosity, create greaterNot all Roman concrete was good stufthere are notable failures referenced in ancientwritings. But the Romans learned from theires, and itÕs useful to note that by theyear 1 A.D., they had been working with theirconcrete far longer than modern man has beenworking with Portland cement! w water to cementitious materialslsbe burned from stone which, whether soft orhard, is in any case white, and lime made ofclose-grained stone of the harder sort will begood in structural parts; lime of porous stone,in stucco.Ó The Romans also selected theother ingredients with care, and were rigidlyprecise in using the same volume measure-ments for each batch, which they mixed insmall batches with a hoe and a trough.Low water to cementitious materials ratio andc o m p a c t i o n .Through trial and error thewhen Joseph Aspdin concocted his fw.s former editorial assistant, contributedcopy pertaining to roller compacted concrete and to the sec-tion ÒMAKING THE REALLY GOOD STUFF S E C R E T S S E C R E T SS E C R E T S Get more information atWWW.ROMANCONCRETE.COM