Masonry Cracking from Slab Shrinkage...How to Repair

[asixth]

Hi guys,

I have a few defect issues that have surfaced on my job that I will be posting in the coming days so I hope you guys can help me out with them. First one:

I have a blockwall which was detailed to be tied into a stressed slab. A pour joint was provided to help mitigate some of the creep and shrinkage movement of the stressed slab, however it was still able to pull to block way which has resulted in some extensive cracking that I will need to "hide".

Can people please comment on the detailing I have provided, I think an ancon dowel or something that can allow some horizontal movmement would have been a much better detail. And a possible remedial method, I was thinking of providing a stainless steel cover plate which will allow any future movement while concealing the cracking. The client has suggested a saw joint (50mm) to initite a failure plane for any future cracking while repair the existing cracking which has occurred. Will a saw joint in blockwall only be effective if the block is cut before cracking occurs.

All comments will be appreciated.

 

[BAretired]

As detailed, cracks are certain to result when the slab is stressed. You would have been better to omit the pour strip. It serves no purpose other than to ensure that cracks will develop in the masonry.

If you are going to stress concrete slabs attached to masonry, try to ensure that you provide a joint in the masonry at the ends of the prestressed slab.

BA

 

[asixth]

I provided the pour strip to allow some of the shrinkage and creep-shortening to occur before the block is tied in. As you can see from the photo's, this did not work as well as I envisioned, a control joint to allow the face of the blockwall to move away from the returns would certainly have been a better detail.

I know this may sound stupid, but can a control joint be "post-installed"?

 

[Ron]

asixth...your "control" joint has already been put in place....the crack. Now all you have to do is clean it up.

Remove the mortar interface at the solid wall and provide a sealant joint. Patch the crack with epoxy.

 

[hokie66]

asixth,

I would consider sawing a joint up the outside corner, say half the thickness of the wall, if that would not interfere with the structural integrity of the system. Insert a backer rod and sealant to suit. Inside, it depends on whether there is a finish material (not applied) which will cover the crack. If so, just leave it alone.

Filling the crack with epoxy or a rigid material won't work, as you still have a lot of shrinkage to go.

A control joint at the corner may have avoided the problem. But concrete block is a very brittle material, and sometimes it is very difficult to predict where cracking will occur. When block tries to restrain concrete shrinkage, the block will lose every time.