Often asked: Can you cut into a post tension slab?

PT slabs on ground can be placed and stamped just like with any other concrete slab. Surfaces can be stained or overlaid. The only concern is to always remember not to cut or drill into post-tensioned concrete slabs, since once a tendon has been cut, it is very difficult to repair.

What happens if you cut a post tension slab?

Once the concrete is poured and sets, the cables are tensioned. Once tensioned, the cables cannot be de-tensioned. The hazard exists when workers cut into the slab and rupture the tensioned cable. Do NOT cut into a post tensioned slab if there is a chance you will rupture a cable.

How deep are the cables in a post tension slab?

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. When in doubt, mark it out and avoid it!

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.

Can a post tension slab be repaired?

Post tension (PT) tendon systems are primarily used for large slab construction projects. Since the early 1950’s, post tension tendons have been used in the design of concrete structures. For such critical structural element, the repair should only be completed using a certified, experienced repair contractor.

Can post tension slabs crack?

Post-tensioned concrete slabs are typically expected to crack less than other slabs because post-tensioning produces a compressive stress that must be exceeded before enough tensile stress develops to cause cracking. For a 100,000 ft2 post-tensioned slab, this would result in an estimated 900 lineal ft of cracks.

Can you cut prestressed concrete?

Cutting or minor trimmings at the ends are okay and should not cause any problems but cutting near the centre can affect the lintel’s load capacity. It is important to consult a structural engineer before any cutting is done.

How much does it cost to replace a post tension cable?

The cost of a single cable repair will typically range from $800 to $1,200 and does not include the cost of other concrete repair. In most slab systems, the cables are spaced about 30 to 36 inches apart. As a result, a significant expense for cable repairs can be experienced.

How long does post tension slab last?

Conventional concrete & rebar foundations last about 20-30 years before failure begins to occur. Post-tension slabs are lasting about 15-20 years and are failing at a much higher rate. Post-tension slabs are created with concrete trenches around the perimeter of the house where the external walls will be placed.

What are the disadvantages of Post-Tensioning?

Here are a few disadvantages of post tension slabs:

• Since there are a number of tendons and wires spread inside the post tension slab, it can result in corrosion.
• Complexity of work: The post tension slab can be made only by skillful professionals.

Which is better pre tensioning or post-tensioning?

Pre-tensioning is preferred when the structural element is small and easy to transport. Post-tensioning is preferred when the structural element is heavy.

Why do we use post tension?

Designers use post-tensioning as a way to reinforce concrete by prestressing it. In prestressed members, compressive stresses are introduced into the concrete to reduce tensile stresses resulting from applied loads including the self weight of the member (dead load).

How do you fix exposed post tension cable?

Post-Tension Slab Cable Repairs To repair, purchase some concrete patch from the hardware store. Using a putty knife or a hand trowel to apply the concrete patch to the exposed cable end. “Trick of the trade” wiping the surface off with a damp sponge will remove excess silicone and leave a smooth finish.

What is post tension cable repair?

Corrosion can occur in grouted and ungrouted post-tension structures leaading to post-tension cable repair, in the presence of moisture and air in voids along the cable tendon. Post-Tech® PT Cable Drying is a corrosion mitigation process where the moist air from the PT cable is replaced by dry non-corrosive air.

How do you Detension a post tension cable?

The pictures below show an example of how to detension the tendons with a Detensioning Tool.

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