Prestressed Concrete
PRESTRESSED CONCRETE The development of early cracks in reinforced concrete due to incompatibility in the strains of steel & concrete was perhaps the starting point in the development of new material like “Prestressed Concrete”. Prestressed Concrete is a method for overcoming concrete’s natural weakness in tension.
INTRODUCTION
Prestressed Concrete is basically concrete in which internal stresses of suitable magnitude & distribution are introduced, so that the stresses resulting from external loads are counteracted to a desired degree.
MATERIALS USED IN PRESTRESSED CONCRETE
(1) CEMENT –
The cement used shall be any of the following, with the prior Approval of the engineer-in-charge:
Ordinary Portland cement conforming to IS : 269-1976”;
Portland slag cement conforming to IS : 4551976t, but with not more than 50 percent slag content;
Rapid-hardening Portland cement conforming to IS : 8041-1978;
High strength ordinary Portland cement conforming to IS : 8112- 19765.
( 2) AGGREGATES-
The nominal maximum size of coarse aggregate shall be as large as possible subject to the following:
In-no case greater than one-fourth the minimum thickness of the member, provided that the concrete can be placed without difficulty so as to surround all prestressing tendons and reinforcements And fill the corners of the form.
It shall be 5 mm less than the spacing between the cables, strands or sheathings where provided.
Not more than 40 mm; aggregates having a maximum nominal size of 20 mm or smaller are generally considered satisfactory.
Coarse and fine aggregates shall be batched separately.
(3) WATER-
The requirements of water used for mixing and curing shall conform to the requirements given in IS : 456. However, use of sea water is prohibited.
(4)ADMIXTURES –
Admixtures may be used with the approval of the Engineer-in-charge. However use of any
INTRODUCTION
Prestressed Concrete is basically concrete in which internal stresses of suitable magnitude & distribution are introduced, so that the stresses resulting from external loads are counteracted to a desired degree.
MATERIALS USED IN PRESTRESSED CONCRETE
(1) CEMENT –
The cement used shall be any of the following, with the prior Approval of the engineer-in-charge:
Ordinary Portland cement conforming to IS : 269-1976”;
Portland slag cement conforming to IS : 4551976t, but with not more than 50 percent slag content;
Rapid-hardening Portland cement conforming to IS : 8041-1978;
High strength ordinary Portland cement conforming to IS : 8112- 19765.
( 2) AGGREGATES-
The nominal maximum size of coarse aggregate shall be as large as possible subject to the following:
In-no case greater than one-fourth the minimum thickness of the member, provided that the concrete can be placed without difficulty so as to surround all prestressing tendons and reinforcements And fill the corners of the form.
It shall be 5 mm less than the spacing between the cables, strands or sheathings where provided.
Not more than 40 mm; aggregates having a maximum nominal size of 20 mm or smaller are generally considered satisfactory.
Coarse and fine aggregates shall be batched separately.
(3) WATER-
The requirements of water used for mixing and curing shall conform to the requirements given in IS : 456. However, use of sea water is prohibited.
(4)ADMIXTURES –
Admixtures may be used with the approval of the Engineer-in-charge. However use of any