Can post tension cables break?
The same thing happens when post-tension cables break, and the result can be a tendon bursting from the concrete with enough force to cause severe injuries or even death.
When should you tighten post tension cables?
One of the biggest problems with a post tension slab is cracks. The cables laying in the concrete are generally not tightened until at least 7-10 days after the concrete is poured. Since the cables are not stretched or elongated, they cannot provide any crack control in those first few days.
How long do post tension cables last?
about 15-20 years
Post-tension slabs are lasting about 15-20 years and are failing at a much higher rate.
What happens if you cut a cable in a post tension slab?
Cutting a tensioned cable, or tendon, can endanger the contractor and compromise the structural integrity of the slab. Building professionals frequently use ground-penetrating radar (GPR) to locate cables within concrete slabs and reinforce the slab during and after cutting operations.
How deep are the cables in a post tension slab?
8″
The plan maps show the rebar at 3″ depth, and the post-tension cables at 8″ depth. Discerning a post-tension cable from rebar generally requires scanning a larger area to properly understand the layout of structural elements in a slab.
Is post tension better than rebar?
Post-tensioning, which is a form of prestressing, has several advantages over standard reinforcing steel (rebars): It reduces or eliminates shrinkage cracking-therefore no joints, or fewer joints, are needed. Cracks that do form are held tightly together. It allows slabs and other structural members to be thinner.
Are tension cables better than rebar?
Post tension foundations are what tract home and apartment builders use so therefore they are lower quality. Post tension foundations don’t work for our soils. Rebar works better here. Those post tension cables can break one day and go flying out and might kill someone.
Does post-tension slab crack?
Errors that lead to cracks in post-tensioned slabs
As a result, even though post-tensioning is meant to help prevent a slab from cracking, the slab can still crack if the tensioning process is done incorrectly.
Is post-tension better than rebar?
What happens if you drill through post tension cable?
Post-tension slab drilling, cutting, and coring can be incredibly dangerous. Not only is there a risk of structural collapse, but you also risk severe injury and death.
Does post tension slab crack?
Why do post tension slabs crack?
If movement occurs in the foundation prior to tensioning, cracks may occur due to the lack of any reinforcement at that time. Cracks more often occur during curing because the concrete generates heat and expands during the chemical process and shrinks as it cools.
How thick should a post tension slab be?
A residential post-tensioned concrete slab will typically be 8 inches thick and use 3000 psi concrete. Once the concrete has gained strength to 2000 psi, typically within the 3 to 10 days recommended by PTI, the tendons are stressed.
How much weight can a post tension slab hold?
Even between footings, a post-tensioned slab can safely bear about 1,000 pounds per inch of thickness, or about 5,000 pounds for a typical 5-inch-thick residential slab. If more bearing is needed, it’s possible to cut through the slab and pour a pad footing.
What PSI are post tension cables stressed to?
Steel tendons used for post-tensioning typically have a tensile strength of 270,000 pounds per square inch (psi), are about 1/2 inch in diameter, and are stressed to a force of 33,000 pounds. In contrast, a typical piece of rebar will yield about 60,000 psi.
How deep are post tension cables in the slab?
8 inches thick
A residential post-tensioned concrete slab will typically be 8 inches thick and use 3000 psi concrete. Once the concrete has gained strength to 2000 psi, typically within the 3 to 10 days recommended by PTI, the tendons are stressed.
Is post tension slab better than rebar?
Do post tension slabs crack?
Cracks more often occur during curing because the concrete generates heat and expands during the chemical process and shrinks as it cools. Because there is not yet tension on the tendon cables there is no reinforcement to hold the foundation together and cracks often occur during this period of time.
Can post tension slabs crack?
It is concluded that most cracks in post-tensioned slabs on ground are not detrimental to their structural function. Restraint-to-shortening (shrinkage) cracks, because of their typical orientation within the slab dormant zone, have no effect on slab strength or differential slab deflections.