Binding wire is a soft, annealed iron wire used to tie reinforcement steel bars (rebars) at intersections so that the steel cage holds its shape during concrete pouring. It is a small but critical material in every RCC construction. Without binding wire, the entire rebar cage would collapse during concreting.
Binding wire is governed by IS 280 — Specification for Mild Steel Wire for General Engineering Purposes.
Binding wire is a low-carbon mild steel wire, annealed (softened by heat treatment) to make it pliable for hand-twisting around rebars. It is supplied in coils, typically weighing 10 to 100 kg, and is sold by weight.
Binding wire holds the rebars in position without forming part of the reinforcement design. It does not contribute to structural strength.
| Type | Description | Use |
|---|---|---|
| Black Annealed Binding Wire | Plain mild steel, annealed | Standard RCC tying (most common) |
| GI (Galvanised) Binding Wire | Mild steel with zinc coating | Marine, coastal, exposed areas |
| PVC-Coated Binding Wire | Wire with PVC layer | Decorative or specialty uses |
| Stainless Steel Binding Wire | Stainless steel wire | Highly corrosive environments |
Binding wire sizes are referred to by SWG (Standard Wire Gauge) numbers. Higher gauge number = smaller diameter.
| Gauge (SWG) | Diameter (mm) | Common Use |
|---|---|---|
| 14 SWG | 2.03 | Heavy structural tying |
| 16 SWG | 1.63 | Heavy column ties, large dia bars |
| 18 SWG | 1.22 | Most common for general RCC |
| 20 SWG | 0.91 | Light tying, small bars |
| 22 SWG | 0.71 | Decorative/light work |
| Element | Maximum % |
|---|---|
| Carbon (C) | 0.10 |
| Manganese (Mn) | 0.50 |
| Sulphur (S) | 0.060 |
| Phosphorus (P) | 0.060 |
Low carbon content keeps the wire soft and pliable for easy hand-tying.
| Property | Value |
|---|---|
| Tensile Strength | 350 – 550 N/mm² |
| Elongation | 20% (min) |
| Bend Test | 180° bend without cracks |
| Wrap Test | Should wrap closely around a mandrel of same diameter |
Approximate quantity of binding wire per tonne of TMT steel:
| Bar Diameter | Binding Wire per Tonne of Steel |
|---|---|
| 8 mm | 13 – 14 kg |
| 10 mm | 11 – 12 kg |
| 12 mm | 10 – 11 kg |
| 16 mm | 8 – 9 kg |
| 20 mm | 6 – 7 kg |
| 25 mm and above | 4 – 5 kg |
Wrap the wire around the intersection of two bars and twist the ends together with pliers. Cut off excess wire. Used for light slab ties.
Wire is wrapped around one bar and saddled over the second, then twisted. Used at column-beam junctions.
Two strands twisted together provide stronger holding. Used at corners and critical joints.
Crossing wires through the intersection in X-pattern. Used for high-load structures.
Battery-powered rebar tying tools (Makita, Tymark, etc.) speed up the work significantly on large sites.
| Type | Price per kg (Rs) |
|---|---|
| Black Annealed Binding Wire (18 SWG) | 70 – 90 |
| Black Annealed Binding Wire (16 SWG) | 72 – 92 |
| GI Binding Wire (18 SWG) | 120 – 160 |
| PVC-Coated Wire | 150 – 220 |
| Stainless Steel Wire | 500 – 800 |
Binding wire is one of the smallest yet most essential materials at any RCC construction site. The right choice of gauge (most commonly 18 SWG), proper tying technique, and adequate quantity per tonne of steel ensure that the reinforcement cage remains intact during concreting.
Always procure binding wire conforming to IS 280, perform a quick bend test before use, and budget around 10 kg per tonne of TMT steel for estimation purposes.