A rebar shaker might work fine on the first lift if the rebar is very closely spaced, i.e. ~8" on center. The problem is the second and any subsequent lifts. Now you are shaking the rebar in the first lift that is beginning to stiffen and setup. Shaking the bar at this point causes the concrete, particularly the larger aggregate, to be pushed away from the bar, but due to the stiffness of the concrete (partly depending on the time delay between lifts), it now might not flow back and bond with the bar properly. You may have good consolidation in other areas, but you have likely reduced consolidation in one of the most important areas.

arkie is correct. Rebar shaker works great for the first pass only (sometimes second pass for smaller pours). E.g. 20' pour use on first pass of 4' only then have the guys put it away and follow with your typical internal 14' wand. Regards.

Not sure what this is worth for the rebar vibrator, but the block I am planning on using specifically says don't let the pencil vibrator connect to the rebar as it can vibrate the rocks away from the rebar. On the other hand, the rebar vibrator claim that they have run tests and it isn't a problem. For me, I would go with the ICF manufacturer recommended installation practices. Kind of hard to complain if something goes wrong and you weren't doing things the way they said to do them.

I find it hard to believe that self consolidating concrete would not increase the risk of blowouts.

Jonr, a bit of a paradox but the faster it flows away from you the less hydrostatic pressure you have locally. I works fine but I'm not sure it's worth the additional cost. Regards.

]
yetanotherjohn,
What your manufacturer is probably saying is not to use the rebar vibrator for later lifts in the day -- e.g. It works great for the first pass or second pass on smaller jobs but as the concrete sets and lets say you are three hours into the pour and your going from 8' to 12' ---- strong direct vibrating of the rebar as lower passes are setting can cause a wallow out pushing concrete away from bar. I use this type only when i can't easily reach the bottom of the wall. Regards.

TexasICF, I went back and checked and found I had remembered it wrong. In fact, they recommend the opposite of what I remembered. Here is the section of the manual from Quad-lock. I'm now trying to remember where I had heard the "don't vibrate the reinforcing rod". Consolidation / Vibration You MUST ensure concrete is properly consolidated. A pencil vibrator or rodding with a length of rebar is recommended. Due to the required 6" [15cm] slump, heavy vibrating of the wall is not necessary. Use these tips: • Use a small diameter mechanical vibrator (¾" – 1¼" [19mm – 32mm]). • DO NOT OVER VIBRATE! In most cases, vibrating the steel in the wall can adequately consolidate the concrete around it, especially if a 5" [125mm] to 6" [152mm] slump is maintained • Tapping the outside of the wall is not adequate to ensure proper concrete consolidation. • Do not use the vibrator to move concrete laterally in the wall. This can result in segregation of the concrete components and negatively impact the compressive strength of the concrete. • Concrete ‘build up’ on the ties and rebar can be removed using the vibrator or by shaking the vertical rebar. • External variations of mechanical vibration (hammer, orbital sander, and reciprocating saw) provide limited consolidation and are not recommended.