Uncoated stress relieved low relaxation seven-wire (ply) strand for prestressed concrete — IS 14268 (2022) Testing

IS 14268:2022 covers the manufacture, supply and testing of uncoated, stress-relieved, low-relaxation seven-wire steel strands intended for use in prestressed concrete. The standard covers plain, indented and compacted strands.

The 2022 revision covers three strand types: plain, indented and compacted. This is an important expansion from the earlier edition, which primarily covered plain strands.

Chemical testing can include elements such as carbon, silicon, manganese, sulphur, phosphorus, chromium, nickel, molybdenum, copper and aluminium, along with other specified elements where applicable.

Key mechanical tests include tensile strength, breaking load, 0.2 percent proof load and elongation. These tests help establish whether the strand satisfies the specified strength and deformation requirements.

Yes. Testing and inspection include nominal diameter, tolerance, nominal cross-sectional area and nominal mass per unit length. Strand lay length and relevant dimensional characteristics are also evaluated.

The standard provides sampling requirements for mechanical testing, while the BIS product manual specifies control-unit sampling for several inspections and tests. For many listed requirements, five samples are indicated for each control unit.

Yes. Relaxation properties form part of the standard's requirements. The BIS LIMS listing identifies tests for relaxation loss at both 100 hours and 1,000 hours, subject to the applicable testing facility and requirements.

Besides chemical and mechanical properties, the standard addresses surface condition, strand construction, joints, treatment, workmanship and finish, straightness and behaviour during cutting.