Good concrete consolidation is essential. Lack of consolidation can cause voids, rock pockets, honeycombing, and poor bonding with the rebar. In extreme cases, improper consolidation can affect the structural integrity of the walls.
On the other hand, excessive vibration can create bulged walls and blowouts. How much vibration does an ICF wall need, and what is the best way to do it? Good consolidation is a combination of different factors, and vibration is only one of them. Suitable mix design and correct placement technique are critical, but are not discussed in this article.
Vibration and ICFs is an area that generates significant controversy. ICF-related discussion forums reveal a broad range of opinions and method. In finding an effective solution for you, the principles below should provide general guidelines. Even more regrettably, these sub-par methods are still being used by some contractors. Review an up-to-date installation manual or talk to the technical director at your preferred ICF company to get their latest recommendations about consolidation techniques.
If these sources reveal that the form will not withstand internal vibration, consider switching to a more modern ICF design. Jobs with inadequate consolidation not only damage your reputation, but that of the entire industry.
They tested flat panels with 4- and 6-inch cores, as well as a screen grid and waffle grid ICFs. Panels with corners and lintels were also tested. They also filled test panels with a self-consolidating concrete SCC. In every case, walls filled with low-slump mixes had poor consolidation, regardless of the technique used. On the medium slump panels, external vibration scored slightly better, but not nearly as well as those that used an internal vibrator.
High-slump concrete and SCC achieved adequate consolidation with minimal vibration. A stiff mix with a 4-inch slump needs a bigger head. The vibrator should be inserted vertically into the mix, then slowly withdrawn. Vibrators work by allowing air to float up and out of the concrete, so the tip should not be withdrawn faster than the air can move upward, about 3 inches per second.
If the wall is poured in multiple lifts, the vibrator tip should go deep enough to penetrate 3 to 6 in. For proper consolidation, the operator needs to ensure the zones of influence overlap successively so that all areas of the concrete are properly consolidated. Pay Attention to Corners and Lintels Ironically, corners and lintels—the areas that need the most strength—are where poor consolidation is most likely to occur.
But these areas need more vibration, not less. Add extra bracing as needed; each form manufacturer has developed instruction on how to minimize corner movement, using a combination of plywood, zip ties, strapping tape, or additional bracing. Set an additional brace along each side of each window opening as well. Finally, note that the area below each window buck needs to be filled and vibrated separately.
It had an amplitude of. Inserting the vibrator twice per linear foot of wall is tedious, and in many cases impractical.
Never had a problem with a blowout. I believe it will work well in an eight-inch or thicker wall, though. Most recommend a slump of at least 6 inches. Use a pump truck. A reducing hose can reduce splatter and increase efficiency.