Standard Processing Technology for Rebar Extrusion Coupler Connections

Rebar extrusion coupler connection is a widely used mechanical connection method in construction engineering. Known for its high reliability, stable quality, and convenient installation, it has become a mature alternative to traditional welding and lapping methods.

This article provides a standardized and practical overview of the processing technology for rebar extrusion coupler connections, helping engineers and contractors better understand and control on-site quality.

1. Basic Principle and Overview

Rebar extrusion coupler connection, also known as cold extrusion rebar connection, is a type of mechanical rebar joint.

Working Principle

• A high-pressure hydraulic pump is used as the power source.

• An extrusion press applies strong radial pressure to a specially designed steel coupler.

• The coupler undergoes plastic deformation, tightly gripping the transverse and longitudinal ribs of both rebars.

• Load transfer is achieved through friction force and mechanical interlocking between the coupler and rebars.

Key Advantages

• High reliability: Joint strength can reach or exceed the strength of the parent rebar.

• Wide applicability: Suitable for different diameters and grades of rebars, especially where welding is not allowed or difficult.

• No open flame: Safe, environmentally friendly, and unaffected by weather conditions.

• Simple operation: Equipment is easy to use, with short training cycles.

• Stable performance: Minimal influence from human factors, ensuring consistent quality.

2. Pre-Construction Preparation

2.1 Materials and Equipment

Rebars

• Rebar ends must be straight, without bending.

• Cut ends should be perpendicular to the rebar axis, free from burrs or “horse-hoof” shapes.

• Positioning and inspection marks must be clearly marked on the rebar ends.

Extrusion Couplers

• Material, dimensions, and mechanical properties must comply with design requirements and relevant standards such as JGJ 107 – Technical Specification for Mechanical Splicing of Steel Reinforcing Bars.

• The surface must display manufacturer identification, extrusion mark lines, and rebar size codes.

• No cracks, corrosion, or visible defects are allowed.

Extrusion Equipment

• Extrusion press

• High-pressure hydraulic pump

• High-pressure oil hoses

• Dies matched to the rebar diameter

Auxiliary Tools

• Rebar cutting machine

• Grinding wheel saw

• Marking tools

• Vernier calipers

• Measuring gauges

2.2 Equipment Inspection and Trial Test

• Connect all equipment and check the hydraulic pump, hoses, and press for normal operation.

• Select the correct dies according to the rebar size.

• Before mass production, conduct process qualification tests on site:

  • Produce at least three test joints

  • Perform tensile strength testing

  • Construction can proceed only after test results meet the requirements.

3. Standard Construction Process

(Radial Extrusion Method)

Step 1: Rebar End Preparation and Marking

• Flat cutting: Cut rebar ends flat using a grinding wheel saw or dedicated cutter.

• Rust and impurity removal: Clean rust, oil, cement slurry, and contaminants within approximately 200 mm from the rebar end until metallic luster is visible.

• Marking:

  • Positioning mark: Indicates the insertion depth to ensure both rebars meet at the center of the coupler.

  • Inspection mark: Marked about 2 mm outside the positioning mark to verify rebar displacement after extrusion.

Step 2: Coupler Installation

• Slide the coupler onto one rebar.

• Ensure the extrusion guide lines on the coupler are perpendicular to the extrusion direction for accurate positioning.

Step 3: Alignment and Extrusion

• Insert the second rebar into the coupler until both rebar ends are tightly butted at the center.

• Adjust both rebars so the positioning marks are symmetrically aligned at both ends of the coupler.

• Align the extrusion die with the coupler’s guide marks.

• Start the hydraulic pump and apply pressure:

  • Pressure must reach the rated value specified by the equipment.

  • Maintain pressure for 2–3 seconds, then release.

Extrusion Sequence (Critical)

• Principle: Start from the center and proceed toward both ends.

• Purpose: Eliminate internal air gaps and improve joint compactness.

• Sequence:

  1. Extrude the middle indentation first

  2. Extrude the indentation near the operator

  3. Extrude the indentation at the far end

Step 4: Joint Inspection

Immediately after extrusion, check:

• Indentation depth: Measure the minimum outer diameter using a gauge or caliper; this is the most critical on-site inspection item.

• Number of indentations: Must meet the specified requirements; no missing or insufficient extrusions are allowed.

• Rebar displacement: The inspection mark must be fully pressed into the coupler. Any exposed mark indicates insufficient insertion.

• Appearance: No cracks, folds, or surface defects are permitted.

4. Quality Control Key Points

• Pressure control: Insufficient pressure directly reduces joint strength.

• Correct extrusion sequence: Always follow “center first, then both ends”.

• Accurate marking: Clear and precise marking ensures correct insertion depth.

• Cleanliness: Rebar ends and coupler interiors must be clean and free of contaminants.

• Equipment maintenance: Regularly calibrate pressure gauges and inspect equipment.

• Qualified operators: Personnel must be professionally trained and certified.

• Low-temperature construction: Additional measures are required when ambient temperature is below –20°C.

5. Quality Inspection and Acceptance

Rebar extrusion coupler connections are inspected in two stages:

Process Qualification Test

• Conducted before construction to verify feasibility and reliability of the process.

On-Site Inspection

• Appearance inspection: 100% visual and dimensional inspection (indentation depth and rebar displacement).

• Mechanical performance test:

  • Randomly sample joints from the structure

  • Perform uniaxial tensile tests

  • Acceptance criteria and batch size must strictly follow JGJ 107 requirements.

Conclusion

Rebar extrusion coupler connection is a proven and reliable mechanical splicing technology. Its quality control hinges on three core elements:

Pressure · Sequence · Marking

By strictly following standard procedures and controlling critical steps, high-quality rebar joints can be consistently achieved, ensuring the structural safety and durability of construction projects.

GLUS remains committed to providing standardized couplers, reliable equipment, and professional technical support for global construction projects.