REINFORCING STEEL
1. General
This portion includes the quality aspects of tension, compression, and temperaturereinforcing steel, including welded wire fabric. The work includes furnishing,fabrication, and placement of reinforcement for cast-in-place concrete, including bars,welded wire fabric, ties, and supports.
2. Requirements
2.1 Reinforcing bars
Reinforcing steel shall consist of Mild Steel (MS), Cold Twisted Deformed (CTD) orThermo Mechanically Treated (TMT) bars.
a) Mild steel b) CTD c) TMT
Typical cross sections of MS, CTD and TMT bars.
Type |
Code |
Grade designation |
MS |
IS: 432 |
Fe250 |
CTD, TMT |
IS: 1786 |
Fe415, Fe500, Fe550, Fe500D, Fe550D, Fe600 |
2.2 Welded steel wire fabric
2.3 Tie wire
3. Storage and handling
Proper storage of reinforcement steel
4. Placing of reinforcement
5. Welded joints or mechanical connections
Couplers for reinforcing bars
6. Tolerances
7. Inspection, sampling and testing
Test for reinforcing Steel
|
Test |
Code |
Frequency |
1. |
a) Tensile strength b) Proof stress c) Percentage elongation d) Elongation at maximum force |
IS: 1608, IS: 2062 and IS: 1786 |
2 per cast (For Casts/Heats below 100 tonnes) 3 per cast (For Casts/Heats of 100 tonnes or more) |
2. |
Bend test and Rebend test |
IS: 1599 and IS: 1786 |
-do- |
7.1 Field test for TMT bars
To ensure that TMT bars have a concentric tempered martensite periphery witha softer ferrite-perlite core structure, the Etching test or Ring test as per AnnexAof IS: 1786 shall be carried out.
A small piece (about 12 mm long) can be cut and the transverse face lightlyground flat on progressively finer emery papers up to ‘0’ size.
The sample can be macro etched with nital (5% nitric acid in alcohol) atambient temperature for a few seconds which shall then reveal a darkerannular region corresponding to martensite microstructure and a lighter coreregion.
8 Acceptance criteria
Acceptance or rejection of reinforcement steel is mostly based on tensilestrength. However, other test results of the steel such as chemical composition,bend/rebend is also important.
The test results of reinforcing steel shall deemed to comply with the criteriaspecified in tables .
Chemical composition of high strength deformed bars and wires
Sl. No. |
Constituents |
Permissible maximum percentage |
||||||
Fe415 |
Fe415D |
Fe500 |
Fe500D |
Fe550 |
Fe550D |
Fe600 |
||
1 |
Carbon |
0.30 |
0.25 |
0.30 |
0.25 |
0.30 |
0.25 |
0.30 |
2 |
Sulphur |
0.060 |
0.045 |
0.055 |
0.040 |
0.055 |
0.040 |
0.040 |
3 |
Phosphorous |
0.060 |
0.045 |
0.055 |
0.040 |
0.050 |
0.040 |
0.040 |
4 |
Sulphur and phosphorous |
0.110 |
0.085 |
0.105 |
0.075 |
0.100 |
0.075 |
0.075 |
Nominal cross sectional area, mass and tolerances of steel bars & wires
Nominal size (mm) |
Cross sectional Area (mn2) |
Mass per metre (kg) |
Tolerances in nominal mass (%) |
|
Batch |
Individual |
|||
4 5 6 8 10 12 16 20 25 28 32 36 40 |
12.6 19.6 28.3 50.3 78.6 113.1 201.1 314.3 491.1 615.8 804.6 1018.3 1257.2 |
0.099 0.154 0.222 0.395 0.617 0.888 1.580 2.470 3.850 4.830 6.310 7.990 9.860 |
±7 ±7 ±7 ±7 ±7 ±5 ±5 ±3 ±3 ±3 ±3 ±3 ±3 |
-8 -8 -8 -8 -8 -6 -6 -4 -4 -4 -4 -4 -4 |
NOTE: For the purpose of checking the nominal mass, the density of steel shall be takenas 0.00785 kg/mm2 of the cross-sectional area per metre
Mechanical properties of high strength deformed bars and wires
Test |
Fe415 |
Fe415D |
Fe415S |
Fe500 |
Fe500D |
Fe500S |
Fe550 |
Fe550D |
Fe600 |
0.2 % proof stress/ yield stress Min. (MPa) |
415 |
415 |
415 |
500 |
500 |
500 |
550 |
550 |
600 |
0.2 % proof stress/ yield stress Max. (MPa) |
- |
- |
540 |
- |
- |
625 |
- |
- |
- |
TS/YS ratio (MPa) |
≥1.10, but TS not less than 485 |
≥1.12, but TS not less than 500 |
1.25 |
≥1.08, but TS not less than 545 |
≥1.10, but TS not less than 565 |
1.25 |
≥1.06, but TS not less than 585 |
≥1.08, but TS not less than 600 |
≥1.06, but TS not less than 660 |
Elongation Min. (%) |
14.5 |
18.0 |
20.0 |
12.0 |
16.0 |
18.0 |
10.0 |
14.5 |
10.0 |
Total elongation at max. force Min. (%) |
- |
5 |
10 |
- |
5 |
8 |
- |
5 |
- |
NOTE: TS – Tensile strength; YS -0.2 % proof stress/yield stress
RELATED CODES:
1.IS:228-Methods for chemical analysis of steels.(Parts 1 to 24)
2.IS:226-Structural steel.
3.IS:442-Specification for mild and medium tensile steel bars and harddrawn steel wire for concrete reinforcement:
(Part-1)-Mild steel and medium tensile steel bars.
(Part-2)-Hard drawn steel wire.
4.IS:280-Mild steel wire for general engineering purposes.
5.IS:432-Specification for mild steel and medium tensile steel bars andhard-drawn steel wire for concrete reinforcement:
(Part 1)-Mild steel and medium tensile steel bars.
6.IS:1786-Specification for high strength deformed steel bars and wires forconcrete reinforcement.
7.IS:1566-Specification for hard-drawn steel wire fabric for concretereinforcement.
8.IS:13620-Fusion bonded epoxy coated reinforcing bars –specification
9.IS:10790-Methods of sampling of steel for prestressed and reinforcedconcrete:
(Part 2)-Reinforcing steel.
10.IS:1387-General requirements for the supply of metallurgical materials
11.IS:1599-Method for bend test.
12.IS:1608-Metallic materials - tensile testing at ambient temperature
13.IS:2062-Hot rolled low, medium and high tensile structural steel(6th revision).
14.IS:2502-Code of practice for bending and fixing of bars for concretereinforcement.
15.IS:2770-Methods of testing bond in reinforced concrete:
(Part 1)-Pull-out test.
16.IS:2751-Code of practice for welding of mild steel plain and deformed barsfor reinforced concrete construction.
17.IS:9417-Recommendations for welding cold-worked steel bars forreinforced concrete construction.
18.IS:11587-Structural weather resistant steels.
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