Loss of Air Content in Pumped Concrete Related Information

Mix Design and Pumped Concrete - Civil Engineering Portal

A loss of slump during pumping is normal and should be taken into consideration when proportioning the concrete mixes. A slump loss of 25 mm per 300 meters of conduit length is not unusual, the amount depending upon ambient temperature, length of line, pressure used to move the concrete, moisture content of aggregate at the time of mixing

Re-Examining air content testing for pumped concrete

Oct 17, 2020 · The pressures from pumping seem to cause air to dissolve. This air then returns to the concrete over time. This can cause the concrete producer to introduce air contents that are much higher than needed. This causes a loss of strength and an increase in porosity. Concrete may also be wrongly rejected. 1. Sample concrete before and after the

A Review of ACI 301 Section 4, Concrete Mixtures

Exposure class Maximum w/cm Minimum f' c, psi Air Content Additional requirements 4.5 Exposure Class F2 and F3 3/8" 6.0 5.0 Air Content 1" 6.0 1-1/2" 5.5 4.5 Air Content Exposure Class F1 6.0 5.5 TABLE 4.2.2.1.b.1 — Total air content for concrete exposed to cycles of freezing and thawing 3/4" 7.5 1/2" Nominal maximum size of aggregate, in. 7.0

Air Loss in Fly Ash Concrete| Concrete Construction Magazine

Loss on ignition (LOI) is a measurement of unburned carbon remaining in the ash. Specifications of the American Society for Testing and Materials (ASTM C 618) for fly ash used in concrete limit the LOI to 6 percent. Values greater than 2 to 3 percent, however, will probably require you to significantly increase the air entraining agent dosage.

The effect of air content on concrete strength

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.

Why do we lose air while pumping air entrained concrete

Sep 03, 2020 · Pumping air entrained concrete is a significant challenge for the concrete industry. It is common to lose 1% to 3% volume of air during pumping. This loss

Volume 19/Number 1 Control of Air Content in Concrete

Control of Air Content in Concrete Air-Void Analyzer Figure 1. Freeze-thaw deterioration of non-air-entrained concrete railing. (S44517) Control of Air Content in Concrete New manual provides concrete producers and users with tips on achieving and controlling air in concrete. Air entrainment is a necessary com-ponent of concrete mixtures exposed

CIP 21 Loss of Air Content in Pumped Concrete

It is normal to find a loss of about 0.5 to 1.0 percent air as concrete is conveyed through a pump. However, with long boom pumps, having the boom in an orientation with a long, near-vertical downward section of pipe, the air content at discharge may be less than half of that of the concrete going into the pump …

Air Content Loss in Pump | CZBY CONCRETE PUMP PARTS

May 26, 2015 · If air loss occurs, do not try to solve the problem by increasing the air content delivered to the pump beyond the upper specification limit. High air content concrete with low strength could, or almost surely will be placed in the structure if boom angles are reduced or somewhat lower slump concrete is pumped.

Ready Mix Concrete - Pete Lien

CIP 21 - Loss of Air Content in Pumped Concrete CIP 22 - Grout This information provided courtesy of the National Ready Mixed Concrete Association, Silver Spring, Maryland, USA.

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

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. 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 0.5 to 1.0 percent air as concrete is conveyed through a pump.

CONCRETE TECH-TIP 21

Keep concrete from sliding down the line under its own weight. Where possit;>le, avoid vertical or steep downward boom sections. Be cautious with higslumps, particularly with high cement content mixes and mixes containing silica fume. Steady pumping may help somewhat to minimize air loss…

CIP 21: Loss of Air Content in Pumped Concrete - Kentucky

Kentucky Concrete Association 1 HMB Circle Frankfort, KY 40601 502 695-1535 [email protected]

Air entrainment and its effects in concrete • Aggregate

Jul 12, 2010 · 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

CONCRETE 101

specification requirements which require a specific amount of air content at the point of placement or at the discharge end of the pumping. Air loss can be minimized when pumping by slowing down the "free-fall" of the concrete and minimizing the pumping pressure. 2. What is slump? (Why/what/how it effects concrete and us)

Research - Concrete Pumping Effects on Entrained Air-Voids

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.

TEC LOSS OF AIR - concretesask.org

Loss of Air Content in Pumped Concrete 2:2 HOW TO PREVENT AIR LOSS: 1. Keep concrete from sliding down the line under its own weight. 2. Where, possible, avoid vertical or steep downward boom sections. 3. Be cautious with high slumps, particularly with high cement content …

CONCRETE CONSTRUCTION TROUBLESHOOTING TIPS

Air Loss During Concrete Pumping . Definition: Changes in the air content of the concrete due to concrete pumping operations. Concrete air entrainment requirements are typically based upon concrete sampled and tested from concrete supplied at the end of the chute of the concrete truck. When

Slump Loss When Pumping? - Concrete Engineering general

Nov 23, 2001 · I have personally seen concrete pumped over 200' with a loss of 1-2". And that with a grout injection at the beginning and a concrete with flyash to aid in reducing the heat. At this location it was agree by all parties that the concrete would be tested at each end and the results monitored. We wound up with a 5" slump going in and a 3 coming out.

Air Entrainment and the Properties of Concrete | Concrete

Generally it can be said that air entrainment in concrete reduces the compressive strength of concrete. On the basis of experiments carried out at Road Research Laboratory U.K., 'WRIGHT' has stated that each 1% of air entrained results in the loss of 5.5% in compressive strength of concrete.