What Is Post Tensioning Concrete?

What is the purpose of post-tensioning?

The function of post–tensioning is to place the concrete structure under compression in those regions where load causes tensile stress. Post–tensioning applies a compressive stress on the material, which offsets the tensile stress the concrete might face under loading.

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.

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 a 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 does post-tensioning mean?

OVERVIEW. Post–tensioning is a method of reinforcing (strengthening) concrete or other materials with high-strength steel strands or bars, typically referred to as tendons.

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.

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.

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.

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.

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 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.

How much does a post tension slab cost?

The cost of the post–tensioned 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 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.

What is PT slab in construction?

Post tension slab is a combination of conventional slab reinforcement and additional protruding high-strength steel tendons, which are consequently subjected to tension after the concrete has set. This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any column-free spaces.