Vibrating Concrete in ICF walls

Vibrating poured walls is an accepted norm in commercial construction; in fact, if you don't vibrate; you can expect to have problems with the inspectors, engineers, general contractors, architects, and a host of other people. As you may already know, we at R-Value have a commercial background, and desire to install ICF's at the commercial level of quality; so naturally we would want to vibrate our ICF walls.

Poured walls must be vibrated to ensure complete filling and the elimination of air pockets and voids. This is not just for apprearances! Air pockets are especially prone to form around reinforcing steel, and will significantly reduce the effectiveness of the reinforcement. ICF's add another level of difficulty to the equation, since they have many more ties crossing into the wall than a standard poured wall! These are areas prone to incomplete filling. How should we handle consolidating the concrete in ICF wallsω

What do others doω

Many residential poured wall contractors will tap their walls with a rubber mallet to consolidate the concrete. This works well for them, especially since they tend to pour the concrete "wetter" than commercial projects. If the concrete were poured at the 4"-5" slump required of commercial projects, tapping would not do the job adequatey. I'm told the reason they tap rather than vibrate is because the forms that are commonly used could not withstand the pressure a vibrator adds.

If an aluminum form will not withstand the pressures of internal vibration, how can we expect an ICF form toω Well, we did expect them to! When we first began installing ICF's, we started to vibrate them. At that time we were exclusively using an inexpensive form, and it did not hold the pressure, even with a smaller vibrator as recommended by the industry! So we began to tap the forms. This worked okay, but in order for it to work well, one must pour at least a 6" slump--too wet for quality work. In addition, there were areas of an ICF pour that still wouldn't properly consolidate without an internal vibrator, such as the reinforcement over windows, and filling underneath window openings.

A port for filling and vibrating below windows

A better solutionω

We didn't want to compromise strength or increase the shrinkage and thus crack potential of our walls by increasing the slump, so we sought a better solution. We found some different ICF manufacturers who made stronger blocks. So for a while we would tap the bottom half of the pour, then vibrate the top half. All the reinforcement above window openings is in the top half of the pour. This worked better, but we noticed that sometimes certain types of forms would lift and separate at the seam nearest the bottom of the vibrator! An internal vibrator in an ICF wall is also very time-consuming. These two difficulties would give us problems with the wall height and straightness, so we sought still another solution.

Ultimately we have found the best solution to be in external vibration. This method uses a tool in a cordless drill placed tightly up agains the wall, which shakes a small area of the wall with enough force to liquidate the concrete inside, and allow air bubbles to escape. The vibrator is moved from the bottom of the wall to the top, following along as the walls are filled. This seems to be the best solution so far, since it is both quick and the most effective. We still use an internal vibrator above and below the windows; in these areas, the wall does not lift and separate. One caveat is that the vibrator seems to be a cheap model, and I don't expect it to last too long.

We have our eyes on the latest and greatest external vibrator made for ICF walls--a commercial quality unit that is not cheap. This should speed up production even more, and will likely eliminate the need for using the internal vibrator at all! But we must wait for the finances as this tool costs a commercial price!

Why not just pour it wetω

If you have been wondering what is wrong with just pouring the wall wetter, here is your answer. While it does speed up production, and is certainly easier; increasing the slump of concrete (making it wetter) is detrimental to it's performance. Higher water/cement ratios will significantly decrease the ultimate compressive strength of the concrete, and will also cause it to shrink (and thus crack) more. Since most of the water in concrete is not needed for hydration (the process of curing and hardening the concrete), it is only added for workability. Thus it will evaporate out of the concrete as it cures, and this means that cured concrete occupies less volume than it did when it was wet! The higher the water cement ratio, the greater the volume of water that must evaporate, and the greater the volume change/shrinkage/cracking!

A culture of quality

We seek to develop a culture of quality at R-Value Concrete Structures, even if it means that it takes us a bit more time to complete than our competitors. This is one example of how we approach and solve difficulties in ICF installation. Our methods are a work in progress. I think we learn something from every pour that we make.

Every different brand of ICF has it's own peculiarities that must be mastered. There are several block that will not experience any problems with internal vibration (beyond the time issue), but the majority do have problems, regardless of what the manufacturer claims. This is just one of the reasons that it is important to use an experienced ICF contractor such as R-Value for your ICF installation!

R-Value Concrete Structures has the greatest amount of diverse experience in ICF wall installation in the area. We are able to complete your project on time and on budget and with our experience in quality ICF walls, will make it easy for you or your subcontractors to finish out the project smoothly.

"I'll frame behind Jake (of R-Value) anytime!" Stan Cordts--Cordts Construction