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VACUUM CURING CONCRETE RLOCI by HARPER S. JACA'SOX. Design Engineer, and BLAKE BERRY, .Stiles Manager, Arkhola Sand and G'icet Company, Fort Smith, ,-J,y Looking across the storage yard of the Arkhola Sund and Grace! Company. 7 he two tong cylinders at lejl are the steam and vacuum curing kilns. Alounted on the corner of the building directly abore the in Arkhola can he seen the Elliott taciturn equipment. A rack of green blocks being loaded into the curing kiln at the Arkhola plant. THE use of cement dates baa antiquity, and no one knows a first discovered it or applied knowledge to masonry construed however, the pyramids of Egvpt one of the earliest evidences. Ixi the Romans made a cement cc posed of slack lime and volcanic ; that hardened under water, maki possible the building of their gr< aqueducts in 67 B.C. that broug water front far-off Caul. After t fall of Rome, not again until abo the eighteenth century was any si nificant amount of concrete masom construction used, and just within tl past hundred years a large industt has built up around its use. Around the turn of the century th concrete block industry began t grow. At first, anybody who had sand bank in his back yard could tak a few wooden forms, a few sacks o cement, and some water, and be ii the business. With these methods th< quality and strength of blocks variec considerably. Today, however, the situation is radically different. All ingredients are accurately measured and thoroughly mixed. Further, the concrete mixture is fed into rapidly vibrating steel molds which eliminate large air pockets, and in most modern plants the blocks are steam cured. The Arkhola Sand and Gravel Company, Fort Smith, Arkansas, pictured here, goes a step further and subjects the block to an additional vacuum curing process. The vacuum equipment for this new curing process was designed and supplied by Elliott Company. The significance of this further cur ing under vacuum lies in the advan tage of reducing the moisture content PAGE 10 POWERFAX. SUMMER 1954