Post-tensioning is a concrete reinforcement technique that involves placing steel cables in ducts before pouring concrete and then stressing them after the concrete has gained strength. There are two main types of post-tensioning: unbonded, where the strands are not bonded to the concrete, and bonded, where strands are embedded in ducts within the concrete. This technique is widely used in constructing bridges, buildings, and other structures, allowing for longer spans, thinner sections, and enhanced resistance to cracking and environmental stresses.

1. A Post Tension Primer
Post-tensioning is a technique for reinforcing concrete structures. The prestressing steel cables inside
the sleeves or plastic ducts are positioned in the forms before placing the concrete. As the concrete
gains strength, the cables are stressed to design forces before the application of the service load and are
anchored att the outer edge region of the concrete.
Post-tensioning is a type of prestressing which means that before the concrete has to support the
service load, the steel is pulled or tensioned. The post-tensioned concrete means that the tension is
applied after pouring the concrete, however before applying service loads, it is still stressed and hence it
is called prestressed.[1]
The basic element of a post-tensioning system is called a tendon. One or more pieces of post tensioning
strand are coated with a protective corrosion inhibiting coating and a sheathing or bare strands with a
duct is used to house them. In order to transmit the forces into the structure, there are anchors on each
end of the tendon. The term post-tensioned tendon consists of a complete assembly which contains the
strand or bar, anchorage assembly, the duct and any corrosion-inhibiting coating. [2]
Strands today consist of seven high-strength steel wires are wound together to form a 270ksi strand.
One or more strands would comprise a tendon.[3]
Types of post-tensioning
Two main types of post-tensioning exist :
Unbonded
Bonded (grouted)
Unbonded tendons
In unbonded tendon, the strands are sheathed and not actually bonded to the concrete surrounding it.
One of the most common example are monostrand tendons. They contain corrosion inhibiting grease
coated seven wire strands. The anchorage has a two-piece conical wedge for gripping the strand and a
high strength iron casting.
Bonded tendons
Bonded systems consist of a metal or plastic duct embedded in the concrete in which two or more
strands are inserted. A large multi-strand jack is used to apply stress on these strands and is anchored in
a common anchorage device. The most common use of the Bonded system is used in bridges, in cable-
stayed bridges, in the superstructure (the roadway) and the cable-stays.
The heavily loaded beams in buildings make use of bonded systems.
Uses of post-tensioned tendons
Our bridges, residential foundations, parking infrastructure, walls, columns and commercial or
residential buildings make use of Post-tensioning.

2. The post-tensioned reinforcement technique, when used in floor construction, can result in longer spans
between supports or thinner concrete sections. This method proves quite advantageous for the
construction of buildings and structures with open spaces. The reduced thickness of the structural floors
in the building can decrease the ceiling to floor height of each level and also results in the reduction of
the total weight without sacrificing the potential loads.
The use of post-tensioned tendons in bridge construction provides design flexibility allowing quite
demanding geometry requirements which include significant grade changes, complex curves, and
variable super elevation. In stadiums, this technique allows highly creative architectural approach and
long clear spans.
The technique also helps in eliminating the cracks and shrinkage in concrete. Furthermore, post-
tensioning can also help in resisting earthquakes. These advantages have allowed for the construction of
many or our nations bridges, dams and buildings with modern architectural design and increased
functionality and larger open spaces for the users or occupants. For more information please visit here:
https://www.infrastructurepc.com/
Infrastructure Preservation Corporation
Main Office: 5520 Rio vista Drive, Clearwater Florida 33760
Office: 727-372-2900 Ext.24
info@infrastructurepc.com
https://www.infrastructurepc.com/