Bonded Slab Post Tensioning
This can be defined as the method of applying compression force on concrete after it has been poured and cured.
Introduction to Post tensioning and benefits of post tensioning in concrete slab.
Post-tensioning is a method of reinforcing (strengthening) concrete or other materials with high-strength steel strands rebars, typically referred to as tendons. It has the following benefits as compared to unbonded post tensioning.
Bonded post-tensioned concrete is the descriptive term for a method of applying compression after pouring concrete and the curing process (in situ). The concrete is cast around plastic, steel or aluminium curved duct, to follow the area where otherwise tension would occur in the concrete element.
A set of tendons are fished through the duct and the concrete is poured. Once the concrete has hardened, the tendons are tensioned by hydraulic jacks that react against the concrete member itself. When the tendons have stretched sufficiently, according to the design specifications (see Hooke's law), they are wedged in position and maintain tension after the jacks are removed, transferring pressure to the concrete.
The duct is then grouted to protect the tendons from corrosion. This method is commonly used to create monolithic slabs for house construction in locations where expansive soils (such as adobe clay) create problems for the typical perimeter foundation. All stresses from seasonal expansion and contraction of the underlying soil are taken into the entire tensioned slab, which supports the building without significant flexure. Post-tensioning is also used in the construction of various bridges; both after concrete is cured after support by falsework and by the assembly of prefabricated sections, as in the segmental bridge.
The advantages of this system over unbonded post-tensioning are:
Advantages of Post-tensioning
Placement of Tendons