Concora Crush (CCT)

Definition and overview

The Concora Crush Test (CCT) is a standardised method used to measure the crush strength of corrugated medium, specifically the fluted inner layer of corrugated board. It determines the maximum force required to collapse a pre-fluted specimen under controlled conditions, providing a quantifiable measure of its structural integrity and resistance to compression.

The test is carried out on samples prepared with a standard laboratory fluter, ensuring consistent flute profiles for repeatable results. The measured crush strength directly relates to the material’s performance during box manufacturing, stacking, and transport.

Importance in packaging

In the packaging industry, the CCT is an essential quality assurance tool. It allows manufacturers to verify that corrugated medium meets performance requirements before conversion into finished board. High crush strength ensures boxes can resist deformation under stacking loads, protect goods during transport, and maintain their structural integrity throughout the supply chain.

Overview of the standard

TAPPI T 824 is the internationally recognised standard that specifies the procedures, equipment requirements, and specimen preparation methods for conducting the Concora Crush Test. Issued by the Technical Association of the Pulp and Paper Industry, it ensures accuracy and repeatability across different testing laboratories.

Key requirements include:

• Conditioning specimens under controlled temperature and humidity
• Using a standard fluter to create consistent flute profiles
• Applying compression at a defined rate until the specimen collapses

Following TAPPI T 824 enables results to be directly comparable between facilities, providing a reliable basis for material specification and supplier benchmarking.

While TAPPI T 824 focuses on the intrinsic crush strength of pre-fluted medium, other common corrugated tests measure different performance factors:

• Edge Crush Test (ECT) - measures the edgewise compression strength of finished corrugated board, combining liner and medium performance
• Flat Crush Test (FCT) - measures the resistance of fluted medium to crushing when incorporated into board

The CCT assesses raw medium quality before conversion, making it an important first step in packaging performance evaluation. ECT and FCT complement CCT results by evaluating finished board properties.

The Edge Crush Test is a widely used measure for predicting box stacking performance. Manufacturers may use CCT to select an appropriate medium grade, then use ECT to confirm that the assembled board meets load-bearing requirements.

In industries such as e-commerce, food distribution, and industrial goods packaging, ECT ensures that cartons retain their shape and protect contents under high stacking loads. Combining CCT and ECT results provides a complete picture of packaging performance.

Step-by-step procedure

• Specimen preparation - Cut medium to the required size, typically 152.4 mm by 25.4 mm strips, ensuring clean edges. Condition specimens to 23°C ± 1°C and 50% ± 2% relative humidity.
• Fluting - Use a standard Concora laboratory fluter to form the corrugated profile with consistent flute height and pitch.
• Mounting - Place the fluted specimen between platens in the crush fixture, ensuring accurate alignment.
• Testing - Apply compression at the specified rate, typically 12.5 mm/min, until the specimen collapses.
• Recording results - Capture the peak load value (crush strength) and note environmental conditions.

Best practices

• Verify calibration of load cells before testing
• Avoid handling specimens in ways that could deform the flutes
• Perform multiple tests and average results to account for material variability

• CCT - Material-level test, used to assess raw medium quality before conversion into board
• ECT - Finished board test, used to confirm load-bearing capacity in edgewise compression
• FCT - Measures flute performance within finished board under flat compression

Using all three methods together provides comprehensive insight into material and finished product performance.

• Material inconsistencies - Variations in fibre composition and moisture content between batches can affect results. Maintain consistent sourcing and controlled storage.
• Equipment limitations - Ensure fixtures and platens are free from wear and are precisely aligned to prevent skewed results.
• Specimen handling errors - Misalignment or pre-test flute damage can reduce accuracy. Use alignment guides and careful handling practices.

Mecmesin offers advanced motorised test stands and fixtures for performing CCT in compliance with TAPPI T 824. Our OmniTest and MultiTest-dV systems, combined with VectorPro software, provide:

• High-accuracy load measurement to 0.1 N resolution
• Programmable test speeds for full compliance with TAPPI T 824
• Fixtures engineered for perfect specimen alignment
• Automatic data capture, analysis, and reporting for full traceability

These modular systems can also be configured for ECT and FCT testing, allowing complete corrugated performance assessment within one platform.

The Concora Crush Test, as defined in TAPPI T 824, is a critical step in corrugated medium evaluation. When used alongside ECT and FCT, it gives manufacturers a complete understanding of packaging strength and reliability. By using accurate, calibrated Mecmesin systems and following best practice methods, businesses can improve product performance, optimise material use, and ensure compliance with industry standards.

For guidance on selecting the right equipment, interpreting results, or integrating CCT into your quality assurance process, speak to Mecmesin’s technical team. Our consultative approach ensures you get the most effective and reliable solution for your testing needs.