15422Transportation

Transportation of the concrete from the mixer to the site has to be accomplished without any significant change in the slump, w/b ratio, air content, consistency, and temperature. Quality control and quality assurance personnel have to be cognizant of prolonged mixing causes slump loss, and hence lower workability. Consequently, adequate job control must be established so as to prevent delays in delivery. Where practical, withholding some of the superplasticizer until the truck arrives at the site is desirable, provided that proper mixing is exercised. Particularly in the case of high-strength concrete, all mixer trucks should be inspected and certified regularly to comply with NRMCA inspection requirements. In addition, it is vital that water used to wash mixers between loads should be discharged prior to batching for subsequent loads. In lieu of that, provisions can be made to measure and account for the remaining wash water batched for the next load.

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