Bond and cohesion testing in outline: read the result and failure location
Two primed beams are flagged in a food-processing plant's bond report, while selected unprimed locations have satisfactory results. The steel fabricator and fireproofing installer disagree about the cause. You need the test and failure observations reviewed before assigning blame or changing the system.
Read the bond result together with the test method, location, required criteria and observed failure. ASTM E736/E736M's public scope describes tensile cohesion/adhesion measurement perpendicular to the material surface. A result or failure location is evidence for investigation, not automatic proof that the primer, mix or application conditions caused the problem.
Turn the finding into a focused investigation
- Confirm what was tested. Match the report to the member, substrate or coating record, product and application date. Check the agency's method reference and noted limitations. Distinguish this installed-material check from a complete fire-endurance test; the report should not be described as establishing a new hourly rating.
- Understand the apparatus in outline. Public inspection illustrations show an attachment bonded to the material and a controlled tensile measurement. Have the agency explain its actual apparatus and procedure. A public manufacturer bulletin discusses cap and force relationships, but this lesson supplies no cap size, adhesive recipe or pulling instruction.
- Find the actual comparison. Identify the governing criteria and recorded result in the stated units. Ask for clarification if force is given without a clear interpretation or the required value is unstated. Do not adopt a US high-rise table or manufacturer's typical value as this project's universal minimum.
- Read the observed failure location. Ask whether separation was observed within the material or at an interface, and what the agency records about the test itself. Preserve that observation accurately. It can focus review, but does not prove the origin of the defect or settle the fabricator's liability.
- Gather the linked evidence. Provide coating identity, preparation, application, conditions and prior decisions to the manufacturer and consultant through the project process. Include differences between tested locations without assuming an unprimed pass proves every primed failure has one cause. Request the required investigation and correction for the affected scope.
- Track the response to closure. Keep further tests, directed repairs, sample-location restoration and acceptance linked to the original report. Arrange access before enclosure. Do not replace a flagged result with a favourable retest while losing the original finding or leaving its extent unresolved.
Common mistakes
- Equating a tensile result with complete fire-resistance approval.
- Treating failure location as proven root cause.
- Retesting without preserving the original finding and scope.
Checklist
Keep the bond finding complete
- Member, coating and product identified.
- Method and actual comparison criteria.
- Result units and agency interpretation.
- Observed failure location and limitations.
- Linked evidence and technical response.
- Repairs, follow-up and acceptance record.
Check your understanding
Only the selected primed locations are flagged. Does that prove the primer is the cause?
