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Ordinarily the most representative sample will be taken at the point of final discharge.For safety reasons, however, it is not always practical to do so.(Sec 501.3.2) Optimized mix designs may have a reduction in cement of 0.5 sack per cubic yard from the table shown in Sec 501.3.6 of the Standard Specifications.If cement is reduced, the mixture may be subject to review and approval by the engineer.Combining values from the two systems may result in non-conformance with the standard.This standard does not purport to address all of the safety concerns, if any, associated with its use.
The inspector must be familiar with inspection procedures for determining moisture content, scale weights, and inspection of batching equipment, the performance of tests, and reports.When concrete is being pumped our procedure has been to take samples at the truck chute.Usually there is no significant difference unless a new or reconditioned pump is being used, the concrete is being pumped a long distance or if there are high vertical drops in the line. The difference between the truck and the pump should be checked regularly, especially if there are significant changes in drop or distance, and certainly if a different pump is used.If contractor elects to use an optimized mix, the mix design shall be submitted with the target gradation and allowable gradation range.Representative samples may need to be sent to Construction and Materials for laboratory testing.
There has been discussion about the proper place to sample concrete when it is being pumped.