Concrete Products

APR 2012

Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.

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Page 22 of 51

FEATURE COVER STORY Strescon awarded a single contract to Mar- cantonini S.R.L. of Italy and Buford, Ga.- based North American representative MCT Supply, Inc. It called for complete material storage, handling and transfer equipment; Sicoma MP-3750 (3.3-cu.yd. output) and MP1500 (1.3-yd.) planetary mixers; short- run, 5-yd. traveling mix bucket; Compumat Automation controls package; MCT reclaimer for aggregate and process water recycling; and, an insulated metal wall panel enclosure. Most equipment and access structures are galvanized, excepting scales, which are painted. In addition to the insulated build- ing, MCT supplied all lighting, receptacles, and motor controls, and incorporated ½- ton hoists on beams above stations where motors, pulleys, gear boxes and wear plates will need to be accessed for maintenance. As part of the Compumat system, MCT pro- vided interface with Strescon's Dynamic Color Solutions liquid color and JD Edwards EnterpriseOne accounting systems. NIGHT & DAY DIFFERENCE Strescon architectural crews had used a home- made cart to shuttle a mix bucket 20 ft. from undersized-mixers' discharge gates to crane pick point. Succeeding it is a WiFi-controlled, rail-mounted traveling concrete bucket, shut- tling between the mixers and eliminating the need for workers to hook, unhook and "touch down" heavy vessels. During a pouring sched- ule, the mixers and bucket are automatically washed, with process water dispensed to the reclaimer. It separates coarse and fine aggre- gates, which are recycled at the Saint John operation, or by sister OSCO concrete or con- struction businesses. The reclaimer also con- veys slurry to a tank from which water is drawn for recycling back into concrete mixes. The Strescon contract required MCT to ne- gotiate a small exterior/interior footprint for aggregate delivery, storage and transfer. "We had to fit into a limited space because the site is along a river, and also needed to keep the old batch plant running through- out the new plant construction," says MCT President Michael Jamieson. "Our approach to architectural products plants differs from other suppliers. We use a traveling aggregate weigh hopper instead of a weigh belt. The hopper is better designed to empty itself be- tween loads, thus eliminating potential con- tamination. For moisture measurement, we have probes in coarse aggregate bins and at metering belts for sand." Strescon's new architectural line batch plant has 375 tons of aggregate storage across 12 heated bins, enabling an array WWW.CONCRETEPRODUCTS.COM of different materials. Aggregates are weighed in the mobile hopper, controlled through the WiFi-enabled signal, and de- livered to mixers by twin skip hoists. The Compumat-controlled scales and a feeder belt exhibit significantly improved weigh- ing accuracy compared to the old equip- ment, which was prone to over-batching aggregate by 50 to 100 lbs. Three 85-ton silos store fly ash, plus high early and white cement—the latter for- merly dosed by the bag. Powders are screw- conveyed to each mixer's twin scales, which afford redundancy for differing binders and minimize the amount of screw conveyor ex- panse in the tight enclosure space. The conveyors typically charge cement to within ½ percent of target. The two mixers allow Strescon to efficiently produce small to large concrete volumes, and limit the in- stances of using the structural product line's batch plant for larger pours. "The quality of mixes from old to the new system is night and day. We set the plas- ticity coefficient on the Compumat and it repeats batch after batch. Using the old equipment, operators checked consistency by opening mixer access doors," says George Lawson. "We have cut by two-thirds the old 11- to 12-minute cycle of batching, transporting and pouring mixes and elimi- nated much worker exposure to mobile ves- sels that had presented some of greatest safety challenges." our The loader-fed bin is equipped with a hydraulically operated, insulated cover (opposite page, lower right). Aggregates are delivered to a shuttle belt via a pleated conveyor running 380 tons/hour at a 29-deg. angle. The shuttle feeds eight coarse and four fine aggregate bin compartments, individually heated (forced air, stainless steel ducting, above). Galvanized like much of the new batch plant structure, the bin loads a traveling weigh hopper (lower left) for aggregate batching and mixer charging—supplanting a weigh belt. Free of wiring or cabling due to WiFi-enabled controls, the traveling hopper is designed to 'self-clean' to eliminate potential contamination between architectural product batches. It discharges into one of two skip hoist buckets feeding the Sicoma MP-3750 (right) and MP1500 mixers. MCT extended the ag- gregate hopper rails to the outside of the batch plant enclosure, affording Strescon crews ease of main- tenance and the capability of emptying an aggregate bin without mixer pass through. APRIL 2012 | 21

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