IS 10790:2000 (Part 1) is the Indian Standard (BIS) for methods of sampling of steel for prestressed and reinforced concrete, part 1: prestressing steel. This standard specifies the methods for sampling reinforcing steel from a given lot or batch for conducting quality control tests. It defines the lot size, the number of samples to be drawn based on the lot size, and the acceptance criteria for the lot based on test results. It is the primary standard used for quality assurance of reinforcement steel at manufacturing plants and construction sites.
Methods of sampling of steel for prestressed and reinforced concrete, Part 1: Prestressing steel
Key reference values — verify against the current code edition / project specification.
| Reference | Value | Clause |
|---|---|---|
| Scope | Representative sampling of prestressing strand/wire | Scope |
| Criticality | Highest-stress, lowest-error-tolerance material | Critical |
| Lot | One cast/size/grade/process | Procedure |
| Sample | Across reels/coils of the lot — not one reel-end | Critical |
| Then test | Breaking load/proof/elongation/relaxation | Cross-ref |
| NEVER | Coil-tag / convenience acceptance of tendons | Critical |
| Vs Part 2 | Part 1 = prestressing (higher criticality) | Caution |
IS 10790 Part 1:2000 is the method of sampling of prestressing steel — how a *representative* sample of strand/wire is drawn from a consignment so the IS 14268/IS 1785/IS 6003 acceptance tests actually describe the lot. Prestressing steel is the highest-stress, lowest-tolerance-for-error material in a structure, so representative sampling is non-negotiable.
It sits in the prestressing stack:
Prestressing tendons work at a very high fraction of their breaking strength with little reserve, are notch- and corrosion-sensitive, and a tendon failure is sudden and serious. The acceptance tests only protect the structure if the sample is representative:
The engineering point: with prestressing steel there is no margin for an unrepresentative sample — coil-tag or convenience acceptance of tendons is one of the most serious shortcuts possible, because a sub-strength or damaged lot passing into a post-tensioned/pre-tensioned structure is a latent catastrophic failure. This standard makes the acceptance valid.
Scenario: a consignment of IS 14268 strand for a post-tensioned structure.
Step 1 — define the lot: group by cast/size/grade/process; split the consignment into lots per IS 10790 Part 1.
Step 2 — draw representative samples: the standard number/points across reels/coils of the lot — never one convenient sample of one reel.
Step 3 — test: breaking load, 0.2% proof stress, elongation (IS 1608) and relaxation as required.
Step 4 — judge the lot: against the IS 14268 requirements; accept/reject the lot on the valid result.
Step 5 — protect accepted steel: store to prevent corrosion/nicks; stress/grout per IS 8543.
Representative sampling makes the tendon acceptance meaningful; a convenience sample certifies a reel-end, not the tendons going into the structure.
1. Coil-tag / convenience acceptance. Prestressing steel must be sampled per lot — the single most serious tendon shortcut.
2. No proper lot definition. Treating mixed casts/sizes as one lot breaks the statistics.
3. Sampling one reel-end only. Not representative of reels/coils across the consignment.
4. Damaging the sample. Nicks/heat in cutting the sample bias the test (and indicate handling risk).
5. Confusing it with Part 2. Part 1 = prestressing steel; Part 2 = reinforcing steel — different criticality and lots.
IS 10790 Part 1 is reaffirmed and underpins the acceptance of the most safety-critical material in a prestressed structure. Prestressing tendons operate near their breaking strength with little reserve and are notch/corrosion-sensitive; their failure is sudden and serious — so a sub-strength or damaged lot slipping in is a latent catastrophe, and the only defence is that the acceptance tests were run on a representative sample. Coil-tag or convenience acceptance of prestressing steel is among the most dangerous shortcuts in construction. Define lots properly, draw the standard increments across reels/coils, test (IS 1608/relaxation) and judge the lot, and never confuse it with the Part 2 reinforcing-steel sampling — prestressing steel's criticality demands its own discipline. Witness the sampling; on tendons there is no margin for an unrepresentative sample.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Sampling Frequency (Mass Basis) | One sample per 25 tonnes or part thereof from the same cast. | One series of tests per 'test unit', which is typically defined as a mass not exceeding 30-40 tonnes in product standards. | EN 10138-3 (referencing ISO 15630-3) |
| Sample Discard Length from Coil End | A length of at least 3 m shall be discarded. | At least 1 m of material from each end of a coil shall be discarded. | AS/NZS 4672.2:2007 |
| Primary Scope | Methods of sampling. | Test methods (which includes sampling). | ISO 15630-3:2019 |
| Lot/Batch Definition for Sampling | Based on number of coils to be selected from a larger lot (e.g. select 3 from a lot of 16-50 coils). | Based on a 'test unit' of a defined maximum mass from a single cast; every test unit is tested. | ISO 15630-3 / EN 10138-3 |
| Tensile Test Piece Free Length (Strand) | Not specified; refers to test method standard IS 1521. | The free length between the grips shall be at least 600 mm. | ISO 15630-3:2019 |
| Reference to Test Methods | Refers to other IS codes for specific test procedures (e.g., IS 1521 for tensile tests). | Contains the detailed test procedures directly within the standard itself. | ASTM A370-23 |