Foundation, Concrete and Earthquake Engineering

Importance of Dispensers in Application of High-range Water-reducing Admixtures

Water/cement ratio is very important term in concrete technology as a optimum water content produced high strength than a W/C that are not specified from mix design considering aggregate grading, its moisture content and other conditions like environment ( very cold or hot weather). Some high-range water-reducing admixtures have a shortlived effect on the slump of concrete. Therefore, it is expected that these materials will be dispensed as close to placing time as possible. For ready-mix operations, this might mean the use of a truck-mounted dispenser in the form of a calibrated storage tank. The tank will be charged with the admixture at the same time the concrete is loaded. The user can request an increase in slump by injection of a HRWR admixture, and the driver will dispense the required amount into the turning drum. The volume dispensed will be recorded on the delivery ticket. The injection should be performed under pressure through a spray nozzle to thoroughly disperse the admixture into the drum. Field dispensers, consisting of a measuring unit and pump, can be used at the site.

Truck-mounted Dispenser of Admixture
Truck-mounted Dispenser of Admixture
It is incumbent on the concrete producer to take as great an interest in the admixture dispensing equipment as in the rest of the batch plant. Operating personnel should be trained in the proper operation, winterization, maintenance, and calibration of admixture dispensers. Spare parts should be retained as needed for immediate repairs. Regular cleaning and calibration of the systems should be performed by qualified internal personnel or by the admixture suppliers’ service representative. Admixtures have too powerful an influence on the quality of the concrete produced for their dispensing to be given cursory attention.

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