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Re: Elevated post-tensioned slab cracks

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It is always a little risky to opine on cracks one hasn't seen and doesn't have complete information on - i.e. are the cracks over the column lines or at midspan?  are they full-depth ?  has there been previous repair work done on them?

However,  I would agree that what caused the cracks to open is restraint to shrinkage.  Conventional wisdom (?) is that restraint cracks are typically not a structural problem because even if they are full-depth, the sections of the slab will rotate enough under applied moment that there will be enough contact to allow the precompression to be effective.

Probably most of the cracks can be ignored but if they are full-depth and leaking,  they should be routed and sealed.  The 1/4" crack should probably be epoxy-injected,  it may be advisable to grind the edges down flush so that you don't get concrete cracking and spalling that subsequently becomes epoxy cracking.

Gail S. Kelley