Pre-Stressed Wire Strand Testing
(IS 6006 — Prestressing Steel)

Mechanical testing of prestressing wire strands and wires for post-tensioned and pre-tensioned concrete — verifying ultimate tensile strength, proof load, elongation and relaxation per IS 6006.

Overview

What is the Pre-Stressed Wire Strand Testing?

Prestressing Steel Wire Strands are high-strength cold-drawn steel wires twisted into 7-wire strands used in post-tensioned and pre-tensioned concrete structures. They have significantly higher tensile strength (1570–1860 MPa) than conventional rebar and must be tested to strict standards to ensure structural safety in bridges, prestressed floors and tanks.

At Global Lab, prestressing strand testing is conducted as per IS 6006 and ASTM A416 covering breaking load (ultimate tensile force), 1% proof load (yield force at 1% extension), elongation at break, relaxation (1000-hour or 120-hour test) and cross-sectional area determination — all tested in our NABL-calibrated 1000kN UTM.

Breaking Load & 1% Proof Load

Ultimate tensile force and 1% proof load per IS 6006 grade requirements.

Elongation at Break

Minimum 3.5% elongation per IS 6006 for ductility verification.

Relaxation Testing

Low relaxation (Class 2) strand relaxation at 70% UTS per IS 6006.

Mass per Unit Length

Linear mass density measured — used for cross-section area calculation.

NABL Certified Reports

All results on NABL-accredited letterhead per IS 6006 / ASTM A416.

All Strand Types

7-wire strand 9.53, 11.11, 12.7, 15.24mm dia tested per IS 6006.

Test in Action

Pre-Stressed Wire Strand Testing — Site Images

Prestressing Strand in UTM with Wedge Grips

Breaking Load Test at Full UTS

Relaxation Test Setup at 70% UTS

Test Procedure

How the Pre-Stressed Wire Strand Testing is Conducted

1

Sample Preparation

Strand sample cut to minimum 1500mm. Both ends prepared with wedge grips or resin anchors to prevent premature grip failure.
2

Mass & Area Measurement

Linear mass per metre measured. Nominal cross-sectional area calculated from mass per IS 6006.
3

Tensile Test

Load applied at 100 MPa/min in NABL-calibrated UTM. Breaking load and 1% proof load recorded.
4

Elongation Measurement

Gauge length of 500mm marked. Elongation at break measured by joining broken pieces.
5

Relaxation Test (If Specified)

Strand loaded to 70% of actual UTS. Load loss measured at 120 hours and extrapolated to 1000 hours per IS 6006.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
IS 6006	Specification for Uncoated Stress Relieved Strand for Prestressed Concrete	Prestressing Strand	Indian Standard
ASTM A416	Standard Specification for Low-Relaxation Seven-Wire Strand for Prestressed Concrete	Strand Standard	ASTM
IS 1343	Code of Practice for Prestressed Concrete	Prestressed Design	Indian Standard
EN 10138-3	Prestressing Steels — Part 3: Strand	Prestressing Steel	European Standard

Applications

Where is the CAPO Test Used?

Acceptance testing of prestressing strand for bridge and flyover post-tensioning

Pre-tensioned precast beam, slab and pile strand acceptance testing

Batch acceptance of strand coils at prestressing yards and precast plants

Third-party verification of strand from imported or new suppliers

Post-tensioned slab and flat plate strand acceptance for high-rise buildings

Nuclear and industrial structure prestressing strand quality assurance

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsLegally valid IS 6006 / ASTM A416 certificates for all structural projects.

Calibrated 1000kN UTMNABL-calibrated machine with sufficient capacity for all strand sizes.

Relaxation Testing Capability120-hour relaxation tests with 1000-hour extrapolation per IS 6006.

All Strand Diameters9.53, 11.11, 12.7 and 15.24mm dia strands tested.

Fast 3-Day TurnaroundTensile test results and NABL certificate within 3 working days.

Pan-India CoverageMetal testing at all 7 NABL-accredited lab locations.

Pre-Stressed Wire Strand Testing(IS 6006 — Prestressing Steel)