Concrete Consolidation for ICFs 3
March 29th, 2010 | Common Troubleshooting, From the Field
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.
Concrete Consolidation in ICFs 2
March 23rd, 2010 | Common Troubleshooting, From the Field
Last post we went over the proper concrete mix for insulated concrete form walls. Depending on the forms’ size and the concrete core width, the concrete aggregate size and slump should be adjusted accordingly. The ultimate goal is to get the correct compressive strength for the concrete as specified.
Insulated Concrete Form Concrete Placement
The concrete should be placed in 4′-0″ lifts to ensure proper concrete consolidation. Typically if there is more than one concrete pour per project, the walls are poured a story at a time. Concrete is placed in 4′-0″ lifts using several passes around the perimeter of the building plan until either the top of the wall is reached or until the first pour is completed. Concrete should be placed below every window opening through the opening left in the sill of the window buck.
Most Reward builders have found that an overhead boom pump truck is the most efficient method to place the concrete in the Reward walls. With the overhead boom pump truck it is important to slow the velocity of the concrete by reducing the diameter of the hose to 3″ near the end of the line.
During placement, the ICF contractor must keep a close eye all the time on how the concrete is flowing through the forms and around rebar. Be sure the concrete is not getting hung up on rebar or any embedments.
During cold and hot weather, the concrete mix may need to be adjusted to modify its flowability and the rate of concrete placement may also need to be adjusted.
Next post we will cover the actual concrete consolidation and use of internal vibrators with insulating concrete forms.
Concrete Consolidation in ICFs
March 18th, 2010 | Common Troubleshooting, From the Field
Concrete consolidation is a very critical component in the construction of ICF buildings. The consolidation of concrete in the ICF wall is more difficult to inspect after the pour because the forms stay in place. That is why internal vibration and proper concrete mix and placement is important to ensure that there are no voids or honey combing in the wall.
There are three main components that must be evaluated and addressed. Consolidation is a function of all three components.
- Concrete Mix
- Placement
- Consolidation
Concrete Mix Design for ICF
One of the most important aspects of concrete placement is the proper concrete mix design. The flowability of the concrete is crucial. A quality concrete mix can go along way to assure a successful and efficient concrete placement. Proper concrete mix will save time on labor, facilitate concrete consolidation and provide for a successful Reward wall pour. Cutting corners on the concrete mix can add cost and problems when you go to place concrete into the Reward walls. Concrete mix can vary from region to region throughout the country, as the raw materials are different in various areas. Because of the variance in materials and the importance of a quality concrete mix, the best advice is to work closely with the local concrete supplier. Explain to the concrete supplier that you will be placing concrete in Reward insulating concrete forms. Reward cannot provide the specific concrete mix design; we can only provide guidelines for the mix.
A proper Reward concrete mix will incorporate the following guidelines. These guidelines must be conveyed to the concrete supplier. They will have the most knowledge about the materials in the area to design the best mix for the Reward projects.
Concrete Compressive Strength
The 28-day compressive strength of the concrete must be specified to meet the strength used in the design of the Reward walls. The minimum strength that should be specified is 2,500 psi. A slightly higher compressive strength of 3,000 to 4,000 psi can help the flowability and pumpability of the concrete and provide additional strength to the walls with minimal or no additional costs.
Slump for Insulating Concrete Forms
The slump is an important criterion in the concrete mix to allow the concrete to flow and be pumped at an efficient rate. Inadequate slump can create voids and honeycombs in the walls, or put excessive pressure on the forms during concrete placement. Reward generally recommends a concrete slump of 5.5 to 6.5. The core size of the forms will help determine the slump, and the smaller the core size the higher the slump. For example, the proper concrete slump for each size is listed in the table below.
| Form Sizes | 9″ | 11″ | 13″ | 15″ & 17″ |
|---|---|---|---|---|
| ICF Concrete Slump | 6.5″- 7″ |
6″-6.5″ | 5.5″-6″ | 5.5″ |
| Course Aggregate Size | 3/8″ | 3/8″-1/2″ | 1/2″-3/4″ | 3/4″ |
The slump specified must be the slump that arrives in the cement truck at the job site. Water should not be added to the concrete at the job site. Additional water will reduce the compressive strength of the concrete and affect the water to cement ratio.
Aggregate Size for ICF
The aggregate size is also important in providing concrete with the proper strength that will flow well through the insulating concrete forms. A maximum aggregate size of 3/8″ to 1/2″ is recommended for the best results. The risk of too large of aggregate in the forms could create the damming of the concrete within the forms resulting in a void.
As an example, again the smaller the core size needs the smaller aggregate. The proper aggregate for each size of core is listed in the table above.
Insulated Concrete Form Admixtures
Admixtures are ingredients in the concrete other than portland cement, water and aggregates. Some of the effects of admixtures are to improve the pumpability, durability and workability of concrete and for weathering purposes. There are many different types of admixtures available in different parts of the country. Some of types of admixtures include air-entraining, water-reducing, superplasticizers, retarding and accelerating. Fly ash, air, plasticizers and superplasticizers are common admixtures used in concrete in the insulating concrete form industry. The concrete supplier should address admixtures at the concrete mix design stage. The goal should be a good flowable concrete mix.
Be sure to thank our in-house ICF engineer Kelvin D and Darryl U for contributing to these posts. Next post we’ll go over concrete placement techniques.
|
|
9″ iForm |
11″ iForm |
13″ iForm |
15″ & 17″ iForm |
|
Concrete Slump |
6.5″ – 7.0″ |
6.0″ – 6.5″ |
5.5″ – 6.0” |
5.5” |
|
Course Aggregate Size |
3/8” |
3/8”-1/2” |
1/2”-3/4” |
3/4” |
ICF Student Residence Hall Part III
March 11th, 2010 | From the Field, Marketing, Project Showcase
Wrapping up this project highlight I wanted to give some special credit to the guys who actually put this thing together. As Reward is just the insulating concrete forms, some one has to know how to stack ICFs, align ICFs, and pour concrete as well…oh yeah and DESIGN using ICFs.
ICF Construction and Design Team
Owner: Pegasus Group/Carleton College
Architect: LHB
General Contractor: J.E. Dunn Construction
ICF Installer: Northland Concrete and Masonry
ICF Distributor: Cemstone
Some Cool ICF Pictures
The picture above shows a sunny, however frigid day in Minnesota. If you have been up there in the winter months you know it can get pretty serious. But with the dorms needing to be ready for fall semester they worked through the winter in sub freezing temperatures. Many days hit below zero, but luckily ICFs allow for concrete placement and curing with sub freezing temperatures.
This picture below is a meat thermometer(highly sophisticated measurement) stuck in an ICF and the concrete after placement. It shows what the curing temperature is of the concrete…100 degrees. The outside air temperature was under 20 degrees.
Finished Insulating Concrete Form School
Please enjoy the pictures of this awarding winning school.
As the year goes on and hopefully this projects racks up a couple more awards and we’ll post some updates on the continual energy use and any more ambitions from that campus.
Reward on PBS Series Hometime
March 9th, 2010 | From the Field, Marketing
Hometime Television Series and ICFs
Once in awhile an opportunity comes up where we can get our product on TV. It worked out at the end of the year in 2009 to partner with Hometime on PBS, as they planned to build the foundation of a beautiful home out of ICFs just outside of Minneapolis. The show also teamed up with Cemstone, and their pretty blue trucks, in Minnesota for the concrete placement.
Below is the show broken into 5 parts, for ease of downloading. If you would like to request a full version to use for your home shows involving Reward please contact us and we will see what we can do.
I got rid of the embedded players, so to view videos they will download and start when you click a link. Files sizes range from 5mb to 10mb, so please be patient.
ICFs on Hometime Part 1
ICFs on Hometime Part 2
ICFs on Hometime Part 3
ICFs on Hometime Part 4
ICFs on Hometime Part 5
Architect & Designers ICF Toolkit
March 2nd, 2010 | Marketing
ICF Marketing Support
Thought I take a post to announce a newly created brochure that is now available. This brochure, has been created to show our company history, major product lines, highlight benefits of ICFs, showcase a few projects and most importantly declares our pledge as the industry’s best in customer support- from conception of the ICF project until the walls are completed.
Too often we sell ourselves short on our service and support, however with current tough times and the better times ahead, its the innovation and service that will define our industry. Reward has a corporate office with sales and product delivery support, regional sales managers, marketing personnel, technical specialists (remember Darryl U?) and an engineer on staff- all which are corporately employed.
See here our new Toolkit for Designers and Architects to help communicate the benefits of Reward and insulating concrete forms.
Click to launch the full edition in a new window