Control of air content in concrete

  • 84 Pages
  • 0.84 MB
  • 8114 Downloads
  • English
by
Transportation Research Board, National Research Council , Washington, D.C
Concrete -- Air content., Air-entrained conc
StatementD. Whiting and D. Stark.
SeriesNational Cooperative Highway Research Program report,, 258, Report (National Cooperative Highway Research Program) ;, 258.
ContributionsStark, D.
Classifications
LC ClassificationsTE7 .N25 no. 258, TA440 .N25 no. 258
The Physical Object
Pagination84 p. :
ID Numbers
Open LibraryOL3192189M
ISBN 100309035740
LC Control Number83070827

Manual on Control of Air Content in Concrete Pamphlet – January 1, by David A. Whiting (Author), Mohamad A. Nagi (Author) See all formats and editions Hide other formats and editions. Price New from Used from Pamphlet, January 1, "Please retry" Author: David A.

Whiting, Mohamad A. Nagi. COVID Resources. Reliable information about the coronavirus (COVID) is available from the World Health Organization (current situation, international travel).Numerous and frequently-updated resource results are available from this ’s WebJunction has pulled together information and resources to assist library staff as they consider how to handle coronavirus.

Genre/Form: Handbooks and manuals Handbooks, manuals, etc: Additional Physical Format: Online version: Whiting, D. (David).

Details Control of air content in concrete PDF

Manual on control of air content in concrete. Control of Air Content in Concrete (PCA EB)– excerpted in this article—brings together practical state-of-the-art information to control the air content of fresh and hardened concrete in the field.

Concrete pavements and structures in many regions of North America are exposed to very severe winter conditions, including snowfall, the ap.

Water--Changes in water content affect air content by changing both the water-cement ratio and the slump of the concrete. As the water-cement ratio increases, more free water is available for the generation of air bubbles, so air content increases.

Above a slump of 6 to 7 inches, concrete is often too fluid to retain entrained air and air content decreases. MANUAL ON CONTROL OF AIR CONTENT IN CONCRETE. Control of air content in concrete book manual covers the following areas in seven chapters: Chapter 1 - Fundamentals of Air Entrainment; Chapter 2 - Air-Entraining Agents; Chapter 3 - Mixture Proportioning and Measurement of Air Content; Chapter 4 - Effects of Concrete Materials on Control of Air Content; Chapter 5 - Effects of Production Procedures on Control of Air Content Cited by: Air Content Control.

Measurement of air content is an important checking “sensor” for the concrete user to know whether concrete will resist freeze-thaw damage. Because average void spacing decreases as air content increases, an “optimum” air content at which void spacing will prevent the development of excessive pressure due to.

Air-Content Specifications for Exterior Flatwork. Q: Presently, our specifications for exterior flatwork call for a compressive strength of psi with 4% (±1%) entrained air.

I've been told that some municipal agencies require up to 9% entrained air for exterior concrete exposed to freeze-thaw conditions. Air entrainment and concrete Some things every contractor should know about a combination that assures longer-lasting and more attractive concrete This photomicrograph of air entrained plastic concrete suggests how minute bubbles of air function as very small ball bearings which make the concrete more workable than a non-air entrained Size: KB.

The effect of air content on concrete strength. How does air content affect strength. Intentionally entrained air voids improve the resistance of concrete to damage from cycles of freezing and thawing.

Any air voids reduce the strength of concrete, with about a 5% reduction in strength for each 1% increase in the volume of air voids. Buy Control of air content in concrete: Appendix F, state-of-the-art report (Addendum to NCHRP report ) by Whiting, D (ISBN:) from Amazon's Book Author: D Whiting.

The air content of concrete is measured in accordance with the pressure method, ASTM C or by the volumetric method, ASTM C for lightweight concrete or for aggre-gates with high absorptions. For air-entrained concrete, the tolerance on air content as ordered or specified is ±%. Density and Yield: When samples are obtained for strength.

Further information about air content is available in the following publications: Whiting, D. and Nagi, M. A., Manual on Control of Air Content in Concrete, EB, National Ready Mixed Concrete Association and Portland Cement Association,42 pp. Manual on Control of Air Content in Concrete.

Discusses the mechanism and measurements of entrained air and the effect of air on concrete properties. Also reviews the effects of concrete materials, production procedures, construction practices, and field conditions.

This gives them better control over the desired air content. But air-entrained cements can be useful under conditions where there's no way to measure the air content of fresh concrete. The availability of portland cements will be affected for years to come by energy and pollution requirements.

ASTM Method of Air Content Measurement in Concrete. The ASTM test method for pressure air measurement specifies two meters to measure the air content. Type A meter helps in the direct measurement of the change in volume in the concrete.

This is carried out by means of a column of water over the known volume of : Neenu Arjun. Guide to Mass Concrete Reported by ACI Committee ACI R Mass concrete is any volume of concrete with dimensions large enough to require that measures be taken to cope with the generation of heat from hydration of the cement and attendant volume change to minimize cracking.

The air content of the concrete in the mixer drum may increase when the mixer load size is three cubic yards or less while air content may decrease in larger load sizes or if the mixer drum is worn or has concrete buildup on the fins.

 Mix Time – Expect longer mix times with larger load sizes. This test method covers the determination of the air content of freshly mixed concrete. The test determines the air content of freshly mixed concrete exclusive of any air that may exist inside voids within aggregate particles.

For this reason, it is applicable to concrete made with relatively dense aggregate particles and requires determination of the aggregate correction factor (see A variety of standard methods are used for measuring: (a) the total air content in freshly placed concrete in the plastic state such as the ASTM C [1] volumetric method and ASTM C [2.

Increasingly, specifiers are requiring concrete to be tested for air content at the discharge end of concrete pumps at the point of placement in the concrete struc-ture.

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In some cases it is observed that air contents are much lower than that in samples tested at discharge from the truck chute. It is normal to find a loss of about to File Size: KB. The concrete air content was also greatly influenced by its mortar volume. The AEA dosage increased with lower W/B ratio, higher RHA content, and greater mortar volume for the target air contents.

Differences in concrete strength for a given water-cementing materials ratio may result from: (1) changes in the aggregate size, grading, surface texture, shape, strength, and stiffness; (2) differences in types and sources of cementing materials; (3) entrained-air content; (4) the presence of admixtures; and (5) the length of curing time.

File Size: KB. Air content increase by mixing for up to 15 minutes and mixing beyond this time will decrease air content. Entrained air will vary with type, physical condition, speed of the mixer and quantity of concrete that is being : Madeh Izat Hamakareem.

Controlling Air Content in Concrete That is Being Pumped, A Synthesis Study Author: Charles F. Scholer and Jay Grossman Keywords: air content, air-entrained concrete, entrained air, pumping, air voids, SPR Created Date: 1/30/ PM. Air-entrained concrete contains billions of microscopic air cells per cubic foot.

These air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand into when it freezes. Air-entrained concrete is produced using air-entraining portland cement, or by the introduction of air-entraining agents, under careful.

The latest American Society of Concrete Contractors position statement, "Measuring Air Content in Non-Air-Entrained Concrete," conveys contractors' point of view for architects, engineers, owners and other project stakeholders. Field acceptance of concrete. Air content —If the measured air content at delivery is greater than the upper limit of b, a check test of air content will be performed immediately on a new sample from delivery unit.

If the check test fails, the concrete has failed to meet the requirements of this Specification. Air content in fresh concrete. Table Corrosion rates with various admixtures: Phase 3: Prototype slab-wall application Fresh concrete air content. The air content of. 1 represents a control concrete with a super plasti-gauging the freezethaw durability of hardened.

Lately, high air contents of concrete have been occasionally observed in Finland. Problems with the compression strength of weather-resistant concrete structures were discovered in. AIR CONTENT.

Description Control of air content in concrete FB2

OF FRESHLY MIXED CONCRETE. BY THE. PRESSURE METHOD (TYPE B) AASHTO T APPARATUS [ ] Air Meter, Type B, calibrated in accordance with AASHTO T [ ] Basic function check of air meter by IAT [ ] Air chamber can be pressurized to stabilized maximum IPL mark [ ] Pressure loss no more than 1/2 IPL mark in 90 secondsFile Size: 33KB.Field testing on this concrete without the use of the aggregate correction factor shows an air content reading of %, and the concrete is reported as meeting specifications.

However, in reality this concrete may or may not meet specifications because even a very small correction factor would result in this concrete having a lower air content. Testing tip: A typical air content for concrete with a ¾-inch maximum-size aggregate is about 6%, and specified ranges in air content are typically minus 1 ½% and plus 1 .