As long as bubbles still emerge as the concrete vibrator is withdrawn, more vibration is necessary.Contractors sometimes urge workers to complete this time-consuming task "efficiently," meaning quickly, but the result can be a structural failure after the concrete has cured.The mix shall be designed by absolute volume methods or an optimized mix design.
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.
Aggregate suppliers will be designated in Site Manager.
The contractor shall design and submit all concrete mixes to District Materials for review and approval.
The inspector should become familiar with the contents of manufacturer's brochures on the proposed batching equipment to understand its operation.
The contractor will normally have this information.The usual solution which, in many instances, is also a building code requirement is concrete vibration.Concrete vibrators will eliminate air bubbles by vigorously shaking the freshly poured concrete with a mechanical vibrator.Methods described should be tempered with judgment to assure that samples are as nearly as possible representative of the true nature and condition of the concrete sampled.For safety reasons, sampling should always be coordinated through contractor personnel.The proportioning plant inspector is responsible for inspecting control of materials and batching operations.