Less than 85 degrees: Per ASTM C94 unless a shorter time is necessary due to the job conditions, but 1 ½ hours maximum. Air Temperature: Maximum allowable combined mixing, delivery, and placement time. Investigators probe efficacy of 90-minute discharge window in ASTM C94 SeptemSeptemConcrete News Findings in a Ready Mixed Concrete Research & Education Foundation report support reexamination of the 90-minute delivery threshold in ASTM C94, Standard Specification for Ready Mixed Concrete.
Every project, city, engineer, and general contractor is different. Ready-Mix Concrete: Comply with requirements of ASTM C94, and as herein specified.
In this meeting, the parties will discuss a number of issues, but an important scenario is what to do with a concrete truck when it reaches the 90-minute mark. Before any large or unique pours are performed, there should be a pre-pour meeting between the contractor, concrete supplier, and pump operator to ensure a successful and timely pour. In concrete construction, planning and communication are imperative to successful projects. No – ASTM C-94 also states that these limitations can be waved if the slump meets mix design specifications without adding water. Yes - According to ASTM C-94, concrete discharge must be complete within 90 minutes of mixing water with cement and aggregates. When is a concrete truck considered too old to pour? Do you have to send it back? In the past, concrete contractors have tried to sneak old trucks into the pour, but today we have third party testing companies that test the concrete batches. A common issue on job sites is the decision on whether to pour an old concrete truck or send it back.
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