“Is it fine as long as it can be screwed in and connected?” Completely wrong!

If you choose the wrong sleeve grade, at best it will fail acceptance inspection, and at worst it can directly affect the structural safety of an entire building!

Today, in just 3 minutes, we will clearly explain steel rebar coupling sleeve grades so that after reading this, you will never be misled again.

Why do so many projects suffer heavy losses with couplers?

In the field of mechanical rebar splicing, there is a common misconception: “As long as two rebars can be screwed together, everything is fine.”

But in reality:

- If the sleeve grade is chosen incorrectly, tensile tests will directly fail

- Large-scale rework on site may delay the project by half a month

- Especially in seismic structures, the performance of the joint is the safety baseline of the entire building

This is why more and more high-quality projects are becoming increasingly cautious when selecting couplers.

In fact, there are only three sleeve grades!

According to the national standards “Technical Specification for Mechanical Splicing of Reinforcing Bars” JGJ 107-2016 and JG/T 163-2013, rebar joints are classified into three categories:

[Grade I Joint]

Performance characteristics:

- Tensile strength ≥ base rebar material

- Failure occurs in the rebar body, not at the joint

- Best ductility and strongest seismic performance

Application scenarios:

- All seismic structures

- Main reinforcement in beams and columns

- Primary load-bearing components

👉 Conclusion: Grade I must be used in critical locations with no compromise

[Grade II Joint]

Performance characteristics:

- Strength close to base material

- High cost-performance ratio, most widely used

Application scenarios:

- General non-seismic structures

- Slab reinforcement, secondary beams

- Secondary load-bearing components

👉 Conclusion: Grade II can be used in most secondary parts of conventional projects

[Grade III Joint]

⚠️ Clearly not suitable for seismic structures

👉 Gradually phased out in current engineering practice

Three-step selection method (just follow this)

① Check the structure

- Seismic structure → must use Grade I

- Non-seismic structure → Grade II is optional

② Check the position

- Main reinforcement → Grade I

- Secondary components → Grade II

③ Check the drawings

👉 Design requirements have the highest priority. If drawings specify Grade I, Grade II must never be used

Why do some projects still fail even when using Grade I?

There are only three common reasons:

- Poor sleeve material quality

- Unstable machining precision (inconsistent thread depth)

- Improper installation (slippage, insufficient tightening)

Final results:

❌ Third-party tensile testing fails

❌ On-site rework required

❌ Acceptance delays and possible penalties

Why are large projects increasingly focused on “stable brands”?

Taking Gulis as an example, the core value is solving one problem: stable compliance in testing

✔ Stable performance

- Each batch meets Grade I standards

- Failure consistently occurs in the base material

✔ High machining precision

- Accurate threading, smooth installation

- Reduced slipping and jamming issues

✔ Complete supporting services

- Connection process guidance provided

- On-site technical support

- 24-hour response

✔ Full specification coverage

- Left/right thread / variable diameter / upset forging / cold extrusion

- Full range from φ12–φ50

👉 Core value: fewer reworks, easier acceptance, and stable progress

On-site selection recommendations (ready to use)

🏢 High-rise residential / commercial complexes / seismic structures → Main reinforcement: Grade I (prefer stable brands)

🏗 General industrial plants / warehouses → Main reinforcement: Grade I or II → Secondary components: Grade II

🧱 Foundation works → Key parts such as piles and pile caps: prioritize Grade I

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If you are currently working on a project:

- Unsure whether to choose Grade I or Grade II

- Worried about failing acceptance inspection

- Or encountering on-site connection issues

Feel free to leave a comment for consultation. Engineering technicians can provide one-on-one answers.

Follow the brand and avoid pitfalls in rebar connections!