Concrete Pumping Effects on Air-Entrained Voids in

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  • The effects of pumping on the air content and void

    Effect of entrained air voids on the microstructure and

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  • Concrete Pumping Effects on Air-Entrained Voids in

    Jul 02, 1994 · The actual effect of pumping on the air content measured for the concrete is not consistent; in some cases air content has increased, while in others it has decreased. Previous work has shown that pumping causes pressure in the concrete, and this pressure can alter the air-void system.

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  • Air Voids in Concrete: A Study of the Influence of

    Jun 01, 1990 · The number of air voids smaller than 10 æm in diameter, however, was found to represent less than 10 percent of the total number of entrained air voids. These small air voids are thus expected to have little influence on frost durability. The results also indicate that the distribution of the ir-void diameters is influenced by the nature of

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  • Air Entrainment and the Properties of Concrete | Concrete

    Road research Laboratory U.K, it is found that 5% air entrainment increases the compacting factor by 0.07, which would be equal to an increase in slump from 1.2 cm to 5.0 cms. 3. Effect on Strength of Concrete: Generally it can be said that air entrainment in concrete reduces the compressive strength of concrete.

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  • Impact of Concrete Placing Method on Air Content, Air-Void

    Jan 01, 1996 · Concrete Pumping Effects on Entrained Air Voids. Final Report, Research Project T9233 Task 21, for the Washington State Transportation Commission, Washington State Transportation Center, University of Washington, Seattle, June 1994, 97 pp. Google Scholar

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  • Pumping Air Entrained Concrete

    What does this Mean for Concrete? •Air Content and SAM testing after pumping may not be representative of the hardened concrete. •If this is true then concrete should not be rejected for low air or high SAM Number after pumping. •It appears that sampling the concrete prior to pumping is a good indicator of the air void system in the

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  • Air entrainment and concrete - USDA

    This has caused concern about the possible loss of resistance of the concrete to freezing and thawing. The actual effect of pumping on the air content measured for the concrete is not consistent; in some cases air content has increased, while in others it has decreased. Previous work has shown that pumping causes pressure in the concrete, and this pressure can alter the air-void system.

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  • Loss of Air Content in Pumped Concrete — What, why, & how

    "Effects of Pumping Air Entrained Concrete," Washington Aggregates and Concrete Association, March 20, 1991, 12 pp. Dyer, R.M., "An Investigation of Concrete Pumping Pressure and the Effects on the Air Void System of Concrete," Master's Thesis, Department of Civil Engineering, University of Washington, Seattle, Washington, 1991.

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  • Air entrainment and its effects in concrete • Aggregate

    Dec 01, 2019 · It is postulated that while pumping the material will adversely affect the air void structure regardless of the pump rate, the overall change in the structure may be decreased by reducing the retention time of fresh concrete in a pressurized system.

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  • CCRT ASICS - Illinois Ready Mixed Concrete Association

    "Entrapped air" is air that is naturally entrapped in all concrete, occurring without the use of an air entraining agent. These bubbles/voids are larger than entrained air and contribute nothing to durability. Entrapped air is also unstable and can be lost during mixing or certain placement operations, i.e. pumping, vibration. Depending on the

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  • Effect of entrained air voids on the microstructure and

    controversy over how frequently air loss is a problem in pumped concrete. Certainly, it doesn't occur every time, or even most times. However, it does occur of-ten enough to be considered seriously until better solu-tions are developed. There are several mechanisms involved, but air loss will occur if the weight of concrete in a vertical or

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  • Air entrainment and concrete - USDA

    These air voids in air en-t r ained concrete act thus as a safety we r e air entrained concrete speci-m e n s . After 5 years of exposure (663 lessening the effects of sulfate attack on concre t e, air entrainment is also h e l p f u l . Time and again, in labora t o ri e s

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  • Why air content varies, and what you can do about it

    The difficulty in controlling air The amount of air that can be entrained by a given dosage of air-entraining admix-ture (AEA) varies with the properties and proportions of concrete-making materials (see box on page 562). The effect of some factors, such as sand, can be confusing be-cause the effect …

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  • Research - Concrete Pumping Effects on Entrained Air-Voids

    Air Entrained Concrete - Effects on Hardened and Fresh

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  • What happens when there is a large air void in concrete

    Answer (1 of 2): My dear friend Sumit, Air void :- "The ratio of the volume of air space to the total volume of voids in a Soil mass". In HCC, a void is an empty space, other than a crack, in the cement paste that contains nothing but air. The type, size, shape, arrangement and abundance of th

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  • Examination of Air Entrainment Stability Factors of Pumped

    the air void system of the concrete. These problems are addressed on a fundamental level to provide a basis for construction guidelines to avoid or minimize such problems during pumping operations. The air entraining mechanism and the instability of the air void system in the fresh concrete is detailed.

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  • Effect of the entrained air void on strength and

    Oct 15, 2015 · In order to facilitate the development and application of air entraining agents (AEA) in the high performance concrete, entrained air void structure parameters (air void size range from 10 to 1 600 μm) of 28 d sifted mortar were measured by image analysis method. The relationship between the air void size distribution and strength of mortar was studied by methods of grey connection analysis

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  • Concrete pumping and its effect on the air void system

    Jul 05, 2018 · Pumping is the most utilized concrete placement technique on construction sites around the globe. Despite being used since the 1960s, a large portion of the knowledge related to the understanding of the concrete pumping process—especially with a focus on the effect of pumping on the concrete air void system—was generated through experience, and thus creating a need for a research …

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  • Volume 19/Number 1 Control of Air Content in Concrete

    discrete air voids in concrete, termed "entrained air." Non-air-entrained (left side) and properly air-entrained concretes (right side) are shown in Fig. 2. Most of the entrained air bubbles are smaller than the head of a pin (shown). The air voids provide empty spaces within the concrete that act as …

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  • Finishing air-entrained concrete requires a light touch

    Jul 27, 2021 · Finishing air-entrained concrete requires a light touch. When finishing air-entrained concrete, less is more. Hard-troweled surfaces and air-entrained concrete don't mix. If you need to entrain air— that is, if the concrete will experience cycles of freezing and thawing while wet—you should do as little finishing as possible.

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