Hair line crackings in garage floor post tension slab

[Scott Keiper]

I'm not sure about where you live but in Florida 90 percent of the garage floors have hair line cracking.
With post tension slabs Re-bar is seldom used throughout the slab. Consequently, although post-tension slabs will generally hold together, they have a higher propensity for cracking than do slabs built with plenty of re-bar.

[Jeffrey R. Pope]

Originally Posted by skeiper

Consequently, although post-tension slabs will generally hold together, they have a higher propensity for cracking than do slabs built with plenty of re-bar.

Actually, that's not true. PT cables are used to compress the concrete and reduce cracking, whereas rebar is dormant until the concrete cracks.

Although hairline cracks are common in all concrete, they become more of a concern in PT slabs. For cracks to form in PT slabs, they must fist overcome the compression created by the cables.

If they are indeed "hairline," and there are relatively few cracks, I wouldn't be too concerned. Without actually seeing the issue, it's difficult to make any definitive statements.

[Russel Ray]

Originally Posted by jpope

Although hairline cracks are common in all concrete

Depends.

But it takes a conscientious builder, conscientious concrete pourers, and proper technology to prevent hairline cracks. There are several areas here that have been built since 1994 that have no hairline cracks. However, there are, indeed, some other areas where there are, indeed, lots of hairline cracks, also built since 1994. And the difference in cost of the houses? Oh, about a million dollars.

[Robert J. OConnor]

Originally Posted by jpope

Actually, that's not true. PT cables are used to compress the concrete and reduce cracking, whereas rebar is dormant until the concrete cracks.

Although hairline cracks are common in all concrete, they become more of a concern in PT slabs. For cracks to form in PT slabs, they must fist overcome the compression created by the cables.

I agree ...

JMO