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maximum time allowable from concrete batching plant to site

90 Minute Rule - Eng-Tips Engineering Forums

How is concrete mixed at a batching plant?

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What is the Allowed Time for the Concrete Discharge?

Dec 08, 2017 · There is always confusion on site about the required or the allowed time for the concrete discharge. Some say it is 60 minutes, 90 minutes, 120 minutes, etc.

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Maximum Allowable Time From Initial Batching to Placement ...

Maximum Allowable Time From Initial Batching to Placement By Concrete Construction Staff Question: I am involved with a large urban concrete project where concrete delivery is sometimes delayed by traffic congestion. The specification requires concrete placement within 90 minutes of batching at the plant.

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Concrete Discharge Time Requirements - ASCC

This time limita- tion is permitted to be waived by the purchaser if the concrete is of such slump or slump flow after the 1-1/2 h time limit has been reached that it can be placed, without the addition of water, to the batch. This waiver is seldom used because the reasons for allowing the waiver are not well understood.

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90 Minute Rule - Concrete Engineering general discussion ...

The question I was really asking was if concrete is first mixed at the site, why does the 90 minutes (US guideline) actually begin from the time of batching at the plant. This is a requirement in New York State DOT specifications.

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Time limit between placing fresh concrete layers

BS 8500-2 requires concrete to be delivered "within 2 h after the time of loading where transported in truck mixers or agitators or within 1 h after the time of loading where non-agitating equipment is used, unless a shorter time is specified or a longer time permitted by the specifier. These limits are sufficient for normal UK temperatures."

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Mixing and Transporting Concrete

As a general rule of thumb, thirty to sixty minutes of transportation are acceptable on small jobs. At a central or portable ready-mix plant, concrete should be discharged from a truck mixer or agitator truck within two hours. If non-agitating transporting equipment is used, this time is reduced to one hour.

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How Long Can a Ready-mix Truck Wait?| Concrete Construction ...

Oct 27, 2010 · ASTM C-94, Specification for Ready-Mixed Concrete, does place a time requirement on delivered concrete. The document states that discharge of the concrete shall be completed within 1 ½ hours after the introduction of the mixing water to the cement and aggregates, or the introduction of the cement to the aggregates.

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How to build a concrete batching plant

2 days ago · When purchasing a concrete batching plant, the theoretical productivity of the concrete plant ought to be larger than we need. For example, if projects’ required amount of concrete is 70 cubic meters per hour, then we should choose hzs90 concrete plant with a theoretical productivity of 90m³/h, instead of hzs75 concrete plant with 75m³/h.

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2 hour transit time - Concrete Engineering general discussion ...

In the summer, that can be exceeded in under 90 min. necesitating proceedures such as using ice. Assuming the plant is a reputable plant, you will get your best quality concrete by batching the concrete at the plant and placinging it before it gets too hot. The truck should be able to dump in 10 min. if it is being pumped.

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EFFECT OF TRANSIT TIME ON READY MIX CONCRETE

When the transit time of ready mix concrete is high, the initial setting of concrete may take place. To avoid setting of concrete, retarding admixtures can be used to prolong the setting of concrete. While permitting use of retarder, it should be ensured that the suitability and dose of retarder is decided after conducting necessary trials.

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Batching, Mixing, Transporting, and Handling Concrete

When truck mixers are used, ASTM C94 (AASHTO M 157) also limits the time between batching and complete discharge of the concrete at the job site to 1½ hours. ASTM C94 (AASHTO M 157) also limits the number of drum revolutions to 300 times after introduction of water to the cement and aggregates, or the cement to the aggregates.

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Work Plan and Trial Batching Precast Concrete

how QC will monitor the batch plant and hauling equipment operations including the target weights, aggregate moisture content, batch weight tolerances, concrete temperature limits, and accelerated curing requirements (when applicable). 4.2.10 Concrete Admixtures—Adjust admixtures within the allowable limits below. Obtain

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Maximum temperature limits for hot-weather concreting

Others say a temperature higher than 90 ºF (32 ºC) is allowable if the concrete contains a set-retarding admixture. A. ACI 301-16 “Specifications for Structural Concrete” and ACI 305.1-14 “Specification for Hot Weather Concreting” limit the maximum concrete temperature to 95 °F (35 ºC) at the time of discharge. This limit is for ...

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BATCHING AND MIXING

September 1, 2003 CONCRETE MANUAL 5-694.400 BATCHING AND MIXING 5-694.400 5-694.401 CHECKING BATC H PLANT OPERATION Check to ensure accuracy and dependable operati on of the proposed equipment and methods prior to the start of concreting operations and after ma king any changes in the location or arrangement of the batching plant.

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