"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.
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
Jul 12, 2010 · Uses and effects of air entrainment. Air entrainment is the process where many small air bubbles are distibuted into concrete and become part of the matrix that binds the aggregate together in the hardened concrete. These air bubbles are dispersed throughout the hardened cement paste but are not, by definition, part of the paste (Dolch 1984).
4. Effects of Temperature on Concrete Air Content For constant amount of air entraining admixture, the increase of temperature will lead to decline concrete air content. So, if temperature varies considerably during mixture production, it would be required to adjust air entraining admixture to achieve designated air …
•After pumping the hardened air content was on average 1.15x higher in the fresh air content. •For example –After pumping 6% fresh and about 7% in hardened concrete •The fresh measurements after pumping do not seem to represent the performance or properties of the hardened concrete.
The effect of air content on concrete strength. Q. How does air content affect strength? A. 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.
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.
Oct 01, 2011 · The volume and size of the entrained air voids depend on many factors, including the type and amount of air-entraining agent, materials and mix composition, mixing and placing techniques. These issues and concepts relating to freeze-thaw damage and the beneficial effects of air entrainment have been reviewed elsewhere,,, .
1. Effect of Air Entrainment on Concrete Compressive Strength Air entraining admixture is usually introduced when it is desired to increase concrete workability without affecting much reduction in compressive strength. It is claimed that, the place-ability of an air entrained concrete having 7.5 cm slump is better than a non-air entrained
Jul 02, 1994 · Concrete Pumping Effects on Entrained Air-Voids. Pumping is a frequently used method of efficiently transporting concrete from the delivery vehicles to the formwork. Unfortunately, pumping concrete can affect the air content of a concrete mix. This has caused concern about the possible loss of resistance of the concrete to freezing and thawing.
Queries on Concrete, Concrete International, August 1992, p. 71. 5. "Effects of Pumping Air Entrained Concrete," Washington Ag-gregates and Concrete Association, March 20, 1991, 12 pp. 6. Dyer, R.M., "An Investigation of Concrete Pumping Pressure and the Effects on the Air Void System of Concrete…
CONCRETE PUMPING EFFECTS ON ENTRAINED AIR-VOIDS. FINAL REPORT. Pumping is a frequently used method of efficiently transporting concrete from the delivery vehicles to the formwork. Unfortunately, pumping concrete can affect the air content of a concrete mix.
Effect of entrained air voids on the microstructure and
Jul 05, 2018 · Up to10%cash back · The particular effect of pumping on changes in the concrete air void system has been investigated in the past [ 5, 6, 7, 8, 9, 10 ]. The general belief within the North American concrete industry is that pumping reduces air content by two or three percent [ 11 ].
Dec 01, 2019 · In particular, the effects of pumping air-entrained wet mix shotcrete on its air content and air void system are discussed, along with the possible ramifications of using different pump rates. 2 . Equipment, materials, and procedure
The research described in this report investigated the impact concrete pumping has on air-entrained voids in concrete. The study examines the effects of different air contents, pumping time, and pressure has on the air volume and the stability of the air void system. The laboratory tests conducted show a significant amount of air volume was lost in the fresh concrete as a result of pumping.
Concrete Pumping Effects on Entrained Air-Voids Author: William Elkey, Donald J. Janssen, Kenneth C. Hover Subject: Admixtures, Air entraining agents, Air voids, Fly ash, Freeze thaw durability, Lignosulfonate, Mix design, Pressurization, Pumped concrete, Stability (Mechanics), Water reducing agents Keywords