Post-tensioned Foundation Slab

Published on 02 Jul 2021. Written by Reddy Shekar

In today’s world, post-tensioned members are playing a vital role in the construction industry. Due to its wide range of applications, post-tensioned members

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replacing the use of conventional reinforced concrete structures. Nowadays post-tensioned foundation slabs are becoming the best choice for the low-bearing capacity soils. Post-tensioned foundation slabs are considering as a functional and cost-effective solution for shrink-swell soils.

About Post-tensioned foundation slab:

Post-tensioned slabs are typically flat slabs for that reason they are best suited for the construction of foundation slab. A post-tensioned foundation is a slab foundation that is reinforced with stranded steel cables that are tensioned after the concrete hardens. The post-tensioning increases the yield bending moment of the slab and offers a lesser extent to stiffness. Due to this application, cracking during bending will be minimized.

Post-tensioned foundation slabs are suitable for the locations having poor soil conditions. Compared to the conventional concrete foundation slabs, post-tensioned slabs are economical and requires less quantity of materials for the construction. Post-tensioned foundation slabs can be used for the longer spans. Which can also be used to counteract the deflections.

Construction of post-tensioned foundation slab:

1. Tendons are the basic elements in the post-tensioned system. They are made up of with one or more pieces of pre-stressing steel and housed inside a duct or sheathing.
2. In the post-tensioning system, the ducts are placed along with the reinforcement before casting the concrete.
3. The tendons are placed in the ducts after the casting of concrete.
4. The ducts prevent contact between concrete and tendons during the tensioning process.
5. The tendons have anchors on each end to transmit the forces into the structure.
6. Tension will be applied to the tendons with the help of hydraulic jack.
7. Cutting of the tendons after the concrete hardens is the final step in the post-tensioned system.

Devices required:

1. Casting bed
2. Mould or shuttering
3. Ducts
4. Anchoring devices
5. Hydraulic Jack

Advantages of Post-tensioning:

1. Suitable for heavy cast-in-place members.
2. Installation is simple compared to conventional rebar foundation.
3. Maintenance is easier.
4. Economical.
5. The time required for the construction is less.
6. Reduce material use.
7. Fire resistance.
8. Better quality output.

Kit required to develop Post-tensioned Foundation Slab:

• Tendons. Anchors
• Hydraulic Jack

Technologies you will learn by working on Post-tensioned Foundation Slab:

• Post-tensioning

Any Questions?