throughout the depth. The strokes will eliminate anyvoids when the concrete is placed in the cone.If the cone is overfilled, the excess concrete is madeflush with the top of the cone with a straightedge. Thecone is raised from the concrete by raising the conecarefully in a vertical direction. The slump is determinedby measuring the difference between the height of thecone and the height of the concrete specimen (fig. 7-3).The slump is recorded in inches on the quality controlreport.After the slump measurement is completed, the sideof the mix is tapped gently with the tamping rod. Thebehavior of the concrete under this test is a valuableindication of the cohesiveness, workability, andplacability of the concrete mix. If the mix iswell-proportioned, tapping will only cause it to slumplower and retain its original identity, and a poor mix willcrumble, segregate, and fall apart. Normally, the EAsperform three slump tests per truck load of concrete.Another test performed by the EAs on a concrete mix isa concrete strength test. This test is performed to controlthe quality of concrete manufactured in the field, toevaluate the performance of available materials used ina concrete mix, and to establish mix proportions thatgive concrete the required strength.PLANT SAFETY1.2.3.All personnel working in the batch plant areashould wear hard hats at all times.When hoppers are being charged with aclamshell or loader, personnel should stay awayfrom the area of falling aggregate.Housekeeping of the charging area is important.Keep the area clean and free of spoiled materialand overflow.4.5.6.Respirators must be worn by all personnel whenhandling bag or bulk cement.Particular attention should be given to any rashor other irregularities of the skin as it mightindicate “cement poisoning.”Vapor type of goggles should be worn bypersonnel in batch plant operations.TRANSIT MIXER SAFETYThe use of transit mixers on construction projectsimpose traffic problems that must be considered.Caution must be used during backing of the transitmixer. Backing should be controlled by a signalman,positioned so the operator can clearly observe thedirections given. Extrement caution must be used whentraveling on a construction site. The stability of themixer is greatly reduced with the extra weight of theconcrete. Also, the weight of the mixer can crush newlyplaced underground utilities, sink in the mud, cracksidewalks, and so forth. In such cases, a slow speed isrecommended.Some additional safety precautions that must beenforced are as follows:1.2.3.4.Reduce speed before making a turn or applyingthe truck brakes.Secure the discharge chute properly, using thelock provided.Check to make certain other personnel are in theclear before starting the mixer charging ordischarging.Make sure the mixer is stopped before makingany adjustments.7-8
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