Cracking in Thin Set Brick Tilt Up panels

[mzaitz]

Hello,

I looked at a building that was completed in 2011 that was constructed with insulated tilt up concrete panels with thin set brick (8" concrete, 2" insulation and 3" arch concrete). There are parts of the panels where they did not place the architectural layer of concrete and field built brick accents that stick out 1-2" past the face of the panel at quoins and at "pilasters". They also did this at the soldier course headers above windows. The thin set brick is cracked in many locations. The cracks are small but typically run vertical. There are diagonal cracks at some typical locations at the corners of the accent locations. I am trying to determine a likely cause for the cracking and have not seen any obvious issues with the structure (no settlement, etc). The worst cracking appears at the windows. I am thinking many of them may have initiated during lifting but no proof as to that theory. Any thoughts on what causes the cracking?

Thanks,

Mike

 

[RFreund]

When you say "thin set" what is the actual wall section like? I would have thought the brick was cast into the face. However, I read your description as (moving inside to outside) 8" concrete + 2" insulation + 3/8" (?) mortar + 3-5/8" brick? How is the brick anchored to the panel?
Would you be willing to post a couple pictures?
My first thought with mostly vertical cracks is shrinkage. Lifting is another good thought, but I'm not sure how that would create a vertical crack. However, understanding how the brick is anchored could provide some clues.

 

[mzaitz]

RFreund,

The majority of the brick is thin set that is cast into the outer layer of concrete (3") for the insulated concrete panel. The special areas (pilasters, quoins and headers) were theoretically tied back to the structural layer of the tilt up panel with brick ties. My thoughts include thermal (this side is exposed to the sun all day but there are cracks elswhere) and cracking during lifting. I think that leaving out portions of the exterior skin made it worse.

Thanks,

Mike

 

[RFreund]

Thanks for the Added info. I just want to clarify the wall section one more time (sorry). Is it like this at the sections where we see those cracks:

Sidebar: Please eng-tip gods allow me to copy and paste my images/screenshots direclty into the reply box.

 

[mzaitz]

The wythe with the thin set brick is about 3". No interior studs at all as it is a gym.

 

[haynewp]

The diagonal cracks from the corners are most likely shrinkage cracks reflecting up through the thin set. Possibly a lack of diagonal reinforcing at the openings or changes in concrete thickness at the arch concrete layer.

 

[RFreund]

Thanks for the clarification and sorry for the delayed response. I'm also going with shrinkage cracks. I've seen vertical cracks at the center of the panels also due to some restraint at the edges of the panel (due to shrinkage and the slight restraint at the edges of the panel).