What happens when a post tension cable breaks?

What happens when a post tension cable breaks?

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.

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.

How long does post tension cables last? Post-tension slabs are lasting about 15-20 years and are failing at a much higher rate.

What happens when a post tension cable breaks? – Related Questions

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.

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Do 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.

Are post tension foundations good?

Advantages of a Post-tensioned foundation

One of the reasons builders choose post-tensioned slabs stems from the relatively poor soil conditions found in the gulf coast region. There are many additional advantages post-tensioned foundations provide aside from their structural performance as well.

Can you add onto a post tension slab?

An addition will typically designed as a conventional (rebar) stiffened slab or post tensioned stiffened slab. If the existing slab is performing well you can usually match the beam depth and rib spacing to expect similar performance.

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.

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.

How do I know if my slab is post tension?

How to tell if you have a post tension slab. Most homes that have post tension slabs have a sign that is stamped into a concrete garage floor, often near the edge of the garage door right in plain sight. Older homes with post tension slabs may have a plastic or paper sign fastened to the wall.

Can post tension cables be replaced?

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. PT Repair and Replacement is the only option for PT cables that were identified as damaged during the post-tension evaluation process.

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How do you inspect a post tension cable?

To determine if you have a post-tension cable foundation, look for the circular blemishes on your foundation. This is where the stressing end pockets were filled with a high strength non-shrink grout, which leaves a visible circular pattern at the perimeter of the exposed foundation.

Why is post-tensioning used?

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).

Why 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.

Where is post-tension slab used?

Post-tensioning 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.

How are post tension cables stressed?

When there is permanent stress and elongation in the post-tension cables, a compressive force is created on the concrete. This compression helps in countering the tensile forces due to load.

What year did post tension slabs start?

Unbonded post-tensioning (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 Post-Tensioning Manual was published in 1972, and provided the fundamentals for PT design and construction.

How deep are post tension cables?

For residential construction, tendons at 48 inches on center are common. Commercial foundations will have much more steel. Tendons can be easily routed around obstructions. A residential post-tensioned concrete slab will typically be 8 inches thick and use 3000 psi concrete.

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How is concrete post-tensioned?

Post-tensioned 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. For an excellent overview of PT, visit the Post-Tensioning Institute.

What is concrete slab on grade?

A slab-on-grade is a type of shallow foundation in which a concrete slab rests directly on the ground below it. A slab-on-grade foundation usually consists of a thin layer of concrete across the entire area of the foundation with thickened footings at the edges or below load bearing walls in the middle of the building.

What is the difference between normal slab and post tension slab?

ØNormal slab is reinforced concrete(RCC) structural element whereas post-tension slab is per-stressed concrete (PSC) structure. In Post tension slab the reinforcement is replaced with cables/ steel tendons. ØIt requires more formwork when compared with the flat slab.

What is the difference between pre tensioning and post tensioning?

Pretension is the technique in which we are imparting tension in strands before placing the concrete. Post tensioning is done by forming a duct in which strands are pulled (tensioned) after the concrete gains it’s full strength. This method is done due to bonding between concrete and steel.

Why we use PT slab?


Due to simplified structural layout of floor and reduced materials used, construction can be carried out faster with less material wastages. Steel laying is a very labour intensive activity, and by reducing the quantity of steel in PT design, the slab can be ready for concreting earlier.

Is post-tensioning system economical?

Both the systems were analysed using SAP and MS Excel program was developed based on the design methodology. The results indicate that Post Tensioned flat slabs are cheaper than the RCC slab systems for all the spans considered in the present study.

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