Quick Answer: What Is Post Tension Concrete?

Why is concrete post tensioned?

PostTensioned Concrete. Designers use posttensioning 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).

What is the benefit of a post tension slab?

Posttensioning, 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.

Where is post tensioned concrete used?

Posttensioning now is used extensively in bridges, elevated slabs (parking structures and residential or commercial buildings), residential foundations, walls, and columns. Jim Rogers Bending and flexing creates high tensile forces that can cause the concrete floor slab to crack.

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Can you cut into post tension slab?

The only concern is to always remember not to cut or drill into posttensioned concrete slabs, since once a tendon has been cut, it is very difficult to repair. Many posttensioned slabs will be stamped to alert the owner and any renovation contractors that the slab is post tensioned.

What happens if you hit a post tension cable?

Cables typically run East to West or North to South. Do NOT cut into a post tensioned slab if there is a chance you will rupture a cable. People have been dismembered and killed when cables are cut and burst out of the concrete.

Which is better pre tensioning or post-tensioning?

This method is developed due to the bonding between the concrete and steel tendons. This method is developed due to bearing. Pretensioning is preferred when the structural element is small and easy to transport. Posttensioning is preferred when the structural element is heavy.

Do post tension slabs have rebar?

Posttension slabs are created with concrete trenches around the perimeter of the house where the external walls will be placed. The top slab of concrete is thinner than with concrete & rebar.

How much does a post tension slab cost?

The cost of the posttensioned slab is $30.52 per square foot which is approximately the average cost of the four floor systems. At the interior supports, a substantial amount of reinforcement was required for ultimate strength.

What year did post tension slabs start?

Unbonded posttensioning (PT) mono-strand tendons have been used in the United States as a form of concrete reinforcement for buildings since the late 1950s (PTI 2006). The first PostTensioning Manual was published in 1972, and provided the fundamentals for PT design and construction.

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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.

What is the difference between pretension and post tension concrete?

Most precast, prestressed concrete is actually pre-tensioned-the steel is pulled before the concrete is poured. Posttensioned concrete means that the concrete is poured and then the tension is applied-but it is still stressed before the loads are applied so it is still prestressed.

What are the advantages and disadvantages of prestressed concrete?

It requires high strength concrete and high tensile strength steel wires. The main disadvantage is construction requires additional special equipment like jacks, anchorage, etc. It requires highly skilled workers under skilled supervision. Construction cost is little higher than RCC structures.

How far apart are post tension cables?

The cables (steel bands wrapped together) are set up within the concrete in a grid pattern (usually about 48 inches apart) and are called tendons when they are covered by a plastic outer shell and held by an anchorage.

How much does it cost to fix 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.

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When should you stress post tension cables?

The best time to apply the stressing would be between 4 and 7 days and certainly before significant loads are applied to the foundation. The strength of the concrete at the time of the stressing should be verified by some type of indirect concrete testing procedure such as an impact hammer or other technique.

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