VH PT SYSTEM

Corporate

Unbonded post-tensioned concrete differs from bonded post-tensioning by providing each individual cable permanent freedom of movement relative to the concrete. To achieve this, each individual tendon is coated with a grease and covered by a plastic sheathing formed in an extrusion process. The transfer of tension to the concrete is achieved by the steel cable acting against steel anchors embedded in the perimeter of the slab. The main disadvantage over bonded post-tensioning is the fact that a cable can destress itself and burst out of the slab if damaged (such as during repair on the slab). The advantages of this system over bonded post-tensioning are:

• The procedure of post-stress grouting is eliminated.
• The ability to individually adjust cables based on poor field conditions (For example: shifting a group of 4 cables around an opening by placing 2 to either side).
• The ability to de-stress the tendons before attempting repair work.

• The characteristics  feature of bonded tendon is that by design , the tendons forms a continuous bond along its length with the concrete surrounding it.
• After stressing of a tendon the grout is injected into the void of the tendon duct.
• When the grout hardens, it locks the movement of the strand within the duct.
• The function of grout is to provide a continuous bond between strand and duct also to increase protection against corrosion by acting as a physical barrier to moisture and chemical penetration.

Applications:

The use of post-tensioned slab systems has been consistently growing in the recent years. Typical applications have been:

• Private residential housing
• Multi storied building
• Offices
• Car parks
• Shopping centers
• Hospitals
• Hotels
• Industrial buildings
• Transverse pre-stressing of bridge deck slabs.