Concrete Consolidation for ICFs 3
March 29th, 2010 | Common Troubleshooting, From the Field | Common Troubleshooting, concrete placement, consolidate, Darryl U, From the Field, kelvin doerr, vibration
As we have discussed so far there are three main components to proper consolidation of concrete in Reward ICFs. We have already addressed the proper mix, and the placement, and now we’ll go over the actual consolidation.
- Concrete Mix for ICF
- Placement of Concrete for ICF
- Consolidation in ICF
Concrete Consolidation
The concrete placed into the Reward walls needs to be consolidated. Consolidation is required to prevent voids, prevent honeycombing and to ensure that there is solid contact made between the concrete and the steel reinforcement. It is important to consolidate the concrete during each concrete lift. Consolidation can be accomplished by using internal vibration.
We do not recommend other types of consolidation as they are not as effective and the iForm can handle internal vibration. The Reward iForm has plastic webs 6 inches on center making the form very strong for concrete placement and consolidation. Additionally with the webs 6 inches on center, there is less EPS foam area being supported by each webs making the form strong during concrete placement and consolidation. This results in a very consistent flat wall with no pillowing or bulging at the horizontal and vertical seams that is typical with forms that have ties 8” or greater on center.
Internal Vibration
This is the best method for consolidating the concrete. A light-duty pencil with a maximum 1″ diameter head size, the lowest frequency or revolutions per minute, a lower motor size of 3/4 to 1 maximum horsepower and the shaft length to meet the wall height vibrator is recommended. The head can be either the squared headed or round head. Darryl U prefers the square head vibrator. The concrete should be stung on each lift and in such a manner that the multiple lifts should be boned together. This can be accomplished by internally stinging thru the current lift and just into the previous lift by a few inches 6” approximately, thus bonding the two together.
Do not use an internal vibrator unless it meets these guidelines. Consolidation using internal vibration method should be done with care to avoid placing excessive internal pressure on the forms.
In order to achieve the best results when using an internal vibrator, it is important to place the head of the vibrator into the concrete fast and remove it slowly from the concrete. This will do the best job of removing the entrapped air from the fresh concrete. Once the head is in the fresh concrete it should be moved slowly but consistently through the concrete.
Around areas of high reinforcement concentration special attention should be given to ensure proper consolidation of the concrete. The rule of thumb for stinging concrete is steady and deliberate when stabbing into the concrete and withdrawing at approximately 1’ per second. The rate of withdraw of the vibrator is also determined by the release of entrapped air in the concrete. and loosen the amounts of congestion inside the form at any given area. Caution should be taken so the vibrator doesn’t touch the sides of the forms. The frequency and amplitude will determine the spacing between the insertions and the rate of withdraw also.
In summary, all three of these aspects must be monitored for each pour. Internal vibration is a must to ensure that the concrete inside of the form work be consolidated to achieve structurally sound walls. These are only guide lines as experience will play into the methods of good technique of internal vibration.
One thing to stress. The most important element of all three is the proper concrete mix. If the mix shows up at job-site at a level not specified…REFUSE the concrete and send it back.
