Concrete Products

AUG 2018

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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44 • August 2018 COVER STORY BY DON MARSH Massachusetts Ready Mix is an early adopter of the Polarmoist optical mois- ture sensor, which Polarmatic North America delivers with software to store calibrations and all aggregate data, plus a box to integrate with Command Alkon and other plant control brands. Concrete Plants Inc. positioned the Polarmoist devices at the new Littleton operation to gauge moisture in aggregate passing from overhead bins to a 12-yd. aggregate batcher. As a non-contacting, remote measurement device, Polarmoist uses LED sources and determines moisture content as percentage of water by weight of dry aggregate. Coarse and fine aggregate can contain respective surface moisture by weight at up to 2 percent and 10 percent—figures that exclude absorbed water volumes ranging from 0.5 to 4 percent, according to Polarmatic NA. Aggregate moisture content must be known to fractions of a percent to minimize variability in concrete quality and support cement optimization. Optical moisture sensors are based on absorption peaks by water molecules at near infrared wavelengths, Polarmatic NA notes. Although well established among process industry operators, such devices have not been widely used in concrete plants due to their high price compared to microwave alternatives. Development of optoelectronic components from communication technology has ushered more economical sensors like those in the Polarmoist moisture probe. — Polarmatic North America, Cincinnati, 603/315-7598; Massachusetts Ready Mix plant construction called for a complete overhaul of the legacy property. Concrete Plants upgraded the exist- ing drive over hopper building (above and top, right) to accommodate deliveries by tri-axle and trailer dump trucks. Coarse and fine aggregates are transferred through a new 60-ft. tunnel to a 180-ft. charge conveyor. Polarmoist is an alternative to the conventional concrete aggregate moisture measure- ment devices—capacitive or microwave sensors, typically in direct contact with aggregate in silos, silo feeders or over a conveyor belt. Such contact causes mechanical wear, in turn requiring occasional sensor recalibration and ultimately plate or entire device replacement. MOISTURE SENSOR: NO POINT OF CONTACT

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