Permissible Extent of Honeycombing and Porosity in Concrete According to International Standards
International Standards Guidance
Most major international codes, including the American Concrete Institute (ACI 301, ACI 318), EN 206 (Europe), and BS 8110 (UK), do not specify a strict numerical limit (such as percentage or area) for honeycombing and porosity in hardened concrete. Instead, they specify performance requirements and acceptance criteria that all concrete must meet. The main criteria focus on the structural integrity, durability, bond with reinforcement, and appearance.
General Acceptance Criteria
Minor surface honeycombing or porosity (shallow and not reaching reinforcement) is generally acceptable if it does not compromise the cover, durability, or structural strength of the element and can be adequately repaired by surface treatment or patching.
Honeycombing or voids that expose reinforcing steel, pass through the section, or are deeper than the specified concrete cover are NOT permissible and must be repaired using approved methods. Extensive honeycombing may require rejection and replacement of the affected concrete.
Key Points from International Standards:
ACI 301-20 ("Specifications for Structural Concrete"):
All voids and honeycombs should be repaired to restore durability and protection of the reinforcement.
Surfaces should be dense, free of loose material, and meet specified appearance requirements.
No structural element should have honeycombing that reduces cover below specified minimums or exposes reinforcement.
EN 206 & EN 13670:
Concrete must exhibit sufficient compactness and surface quality for its intended purpose.
Any defect, including honeycombing, that affects the durability, serviceability, or strength must be assessed and repaired.
BS 8110:
Honeycombing that affects the durability or structural function must be made good with an approved repair material.
Acceptance in Practice
Localized shallow honeycombing (<25mm depth), not extending to the reinforcement and covering <2% of the surface in small patches, is usually deemed repairable and acceptable with proper patching.
Severe or extensive honeycombing (presence around reinforcement, penetrating deep into the member, covering significant surface area) is not permissible and requires evaluation by the supervising engineer.
Summary Table
| Condition | Acceptable? | Required Action |
|---------------------------|------------------------|---------------------------|
| Shallow, local, no rebar exposed, minor area | Yes (with repair) | Patch repair/surface treatment |
| Deep, exposes rebar, reduces cover, extensive | No | Structural repair or replacement |
Note
All repairs must be in accordance with ACI 546R, EN 1504, or other approved repair standards.
Concrete quality and compaction should always be inspected before acceptance.
If in doubt, core samples and non-destructive testing (NDT) should be used as per project specifications.
Professional Support
For expert evaluation and repair solutions, RBS-CONTECH (as part of Iran Concrete Clinic Group) offers specialized engineering, execution, and testing services according to the latest international guidelines.
Website: www.clinicbeton.com, www.rbs-contech.com
Email: clinicbeton.com@gmail.com
Phone: +982188070173, +982188584906
Mobile: +989102333497, +989120916271, +989120916272