What Is Post Tension Concrete?

How does post tension concrete work?

When a concrete slab is stressed by the post – tensioning method, it means the steel is being tensioned and the concrete is being compressed. Putting a concrete slab into compression and the steel into tension before any substantial service loads are applied puts both building materials into their strongest states.

What is the benefit of post tension slab?

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.

What is the difference between pre tensioned and post tensioned concrete?

Most precast, prestressed concrete is actually pre – tensioned -the steel is pulled before the concrete is poured. 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.

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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 in plain sight. Older home’s with post tension slabs may have a plastic or paper sign fastened to the wall.

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.

Can I drill 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.

Which is better post tension or rebar?

Strength. Post – tensioned concrete is stronger and more flexible than conventional steel-reinforced concrete. According to the Concrete Network, post – tensioning helps reduce cracking from shrinkage as the concrete dries, and holds together any cracks that do form.

Why Post Tensioning is done?

The function of post – tensioning is to place the concrete structure under compression in those regions where load causes tensile stress. Sheathing or ducting houses the prestressing steel This allows it to move as necessary when the tensioning force is applied after the concrete cures.

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Do post tension slabs have rebar?

Post – tension 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.

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 Pretensioning and Post Tensioning is done?

Prestressing may be achieved either by pretensioning or by post – tensioning. To pretension concrete the steel is first tensioned in a frame or between anchorages external to the member. Post – tensioned concrete is made by casting concrete that contains ducts through which tendons can be threaded.

Why do we use prestressed concrete?

It is achieved through steel cables that are tensioned and anchored to the concrete. The aim in the use of prestressed concrete is to increase the tensile strength of concrete by introducing an internal compressive stress, counteracting in part the tensile stresses caused by these loads on the structural element.

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.

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.

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Do post tension slabs have beams?

Post – tensioned (PT) slabs are typically flat slabs, band beam and slabs or ribbed slabs. PT slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression.

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