Prestressed Concrete Materials

  1. Concrete

The main factors for concrete used in PSC are:

Ordinary portland cement-based concrete is used but strength usually greater

than 50 N/mm2;

A high early strength is required to enable quicker application of prestress;

A larger elastic modulus is needed to reduce the shortening of the member;

A mix that reduces creep of the concrete to minimize losses of prestress;

You can see the importance creep has in PSC from this graph:

Prestressed Concrete Graph

2.Steel

 

The steel used for has a nominal yield strength of between 1550 to

1800

N/mm2. The different forms the steel may take are:

Wires: individually drawn wires of 7 mm diameter;

Strands: a collection of wires (usually 7) wound together and thus having a

diameter that is different to its area;

Tendon: A collection of strands encased in a duct – only used in posttensioning;

Bar: a specially formed bar of high strength steel of greater than 20 mm

diameter.

bridge beams typically use 15.7 mm diameter (but with an

area

of 150 mm2)7-wire super strand which has a breaking load of 265 kN.

Prestressed Steel Materials

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