How does improper conc. consolidation affect strength? 1

[mdmiller]

I have cast in place formed walls that were not properly vibrated to consolidate the concrete.

How does this affect the strength? Are there any references or articles that address this?

Is there anything that can be done to repair this structurally or would any repair be just cosmetic?

Thanks!!

 

[civilperson]

Visible honey combs and voids may be repaired by chipping back to sound material and then either casting back with repair forms or dry packed. Not all concrete that lacked vibration is poorly consolidated. High slumps and powered screeds will substitute for stingers and vibrators. The best consolidation comes from a casting bed that drops 50-60 times per minute off of 1" eccentric cams. Dragging a chain across the top of concrete can identify voids from the sound heard. Cores or sonographs also work to identify lesser density layers.

 

[msucog]

in my opinion, it makes the process of estimating the strength in place strength much harder. it also makes the "continuity" (for lack of a better word) of the structure unpredictable. in other words, i think it throws a bunch of weak spots in to the structure. here's a question: what if everything was ok except for a 3 inch layer that ran along the wall? you've essentially got a week spot that may be inclined to fail.

if the result is some minor honeycombing, then do as civilperson mentions with chipping and repair. if the problem is something more than surficial, i would not want my stamp on it.

you can evaluate the area (at the expense of the contractor) using ndt methods to more fully check the entire area. then, perform coring to have a better look inside the "suspect" areas and perform compressive strength breaks.

i've even seen times where the contractor was forced to hire their own structural to evaluate the scenario and take responsibility for the wall.

 

[csd72]

I would expect that an even worse problem may be early propogation of cracking due to the stress concentrations around the voids.

Cover to reinforcement would be reduced locally.

also a look at where the concrete is going to be in compression - if the voids are only on the side walls then this may not effct strength much, but this may effect shear capacity in a high shear zone.

These dont account for invisible voids that may be inside the concrete.