icf walls

huangyhg

icf walls
we have just started design of a large institutional project in which the architect wants to use icf (insulated concrete forms) walls. our initial reaction was positive since we would be designing basically 8" solid concrete walls. however we have since heard 'horror' stories about recent projects where substantial voids were encountered in the wall system.
since the insulation stays in place, it would seem difficult to verify full coverage throughout the wall system.
has anyone run into similar problems or determined ways to review on site.
thanks
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i have participated in the design and/or inspection of over 30 projects, with only 2 significant problems. both problem projects had insufficient inspection.
in my experience, the most important point is to treat the  icf installation 'exactly' as a masonry project. insist on low lift (48" max.) grouting, unless several recent project of higher lift can be shown. very careful 'rodding' or gentle vibration is essential. the inspection process is very important.
the type of icf 'cell' configuration has a large bearing on the ease of grout placement and requires careful thought as to the pumping procedure. the grout hose/pipe needs to be moved many, many, many times. grout movement is restricted.
the 'column' type of icf can perform very well, but is usually the most difficult to obtain proper grout consolidation. the systems with larger or more dense 'webs' may hinder grout movement, with a tendency for 'aggregate bridging'.
the reinforcing needs to be well tied and 'tightly' placed. the reinforcing oftentimes holds the icf forms in place, preventing floating or lateral displacement.  if the crews are too concerned about holding the icf blocks in place, the attention to grout consolidation always suffers, as will the project.
we typically didn't have problems with icf, except when the grout was too stiff as pumped. i am not sure if you can vibrate the grout, because that could cause blow-out of the forms. typically, the vertical rebars are "wiggled" during the grout pour, and that seems to work.
there are a lot of different icf's out there. the good systems have an interlocking feature to prevent lateral displacement.
imho, the open web products are far superior to the grid types. even if you get pockets or voids, the overall strength of a 6" or 8" concrete wall greatly exceeds that required by calculation.
thanks for your posts.
the systems we are looking at are open throughout except for the ties. they indicate in their specifications maximum 4'-0" lifts and vibrated using a small pencil vibrator. this seems adequate and may have be written in based on past problems.
i agree that even with the voids due to poor consolidation, the wall will likely be structurally sound. i am more concerned with below grade use and the possibility of water infiltration.
reading manufacturer brochures don't usually give the true picture. your experiences in past projects help ease a 'nervous nellie' engineer.
what has the general level of quality been on projects you have reviewed? we plan on specifying that installation be completed by certified installers by the manufacturer. we are hoping this will prevent the contractor working out of his car doing the work.
quality has been good. i have seen cmu masonry projects that were poorly built, but not icf.
ypu should specify a good waterproofing membrane system for below grade. concrete makes a lousy water barrier, unless it is very low-slump and heavily vibrated.
i have been involved with an icf project once, and i got involved after the origninal contractor and engineer were kicked off the project.
what i found was that the icf forms were all out of plumb and not square.  the concrete used was very poor (next contractor had to install epoxy bolts in the top of the wall, and said drilling in this concrete was "the easiest concrete he's ever drilled.  like drilling through butter".
i think this was the case of no supervision during initial pour and placement of concrete and a lousy first contractor.  i dont blame the icf's, but it has still left a bad taste about using them again.
icf is just beginning to catch on in my area.  i have done 4 to 6 projects with icf.  the good contractors and the good form suppliers are still around.  insist on a contractor with demonstrated experience (visit a current job if you can).  insist on a form system that has a proven track record.  ask questions about the components that they use.  ask to see test reports or speak with their engineering/technical department.