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Honeycomb is a rough and stony concrete appearance with air spaces between aggregates. It may occur due to improper concrete workability and concrete pouring practice, excessive water in the concrete mix, inadequate formwork rigidity and waterproofing, etc.

It is found mostly in beam-column junctions, corners, inaccessible areas where proper compaction is not doable, and steel-congested areas. It also occurs in columns, walls, foundations, but is less likely in beams.

Honeycomb in concrete can cause severe problems if it is spread over a wide area, exposes the steel bars, and extends deep into the concrete (equal or greater than 5 cm). Hence, the affected areas should be repaired as soon as possible. Not only does it distort the appearance of the structural members, but it also reduces structural strength and durability.

Honeycomb in Concrete Wall
Fig. 1: Honeycomb in Concrete Wall

How to Repair Honeycomb in Concrete Structures?

The repair process involves removing loose material, cleaning the affected area, applying suitable repair material, and then curing to gain adequate strength.

Generally, the procedure for the repair of honeycomb in concrete members such as columns and beams is as follows:

  1. Remove loose concrete or loosened aggregate by hammer or wire brush. Prevent the application of large forces such as electrical chippers to avoid sound concrete damage around the honeycomb area.
  2. Clean any dirt or loose material from the area.
  3. Wet the cleaned area before applying the repair material.
  4. Fill small voids and cracks using a mechanical injection pressure pump with a suitable material such as non-shrinkage epoxy grout.
  5. If the honeycomb covers a large area, you may need to create a patch hole to ensure proper bonding.
  6. Place formworks if necessary, and pour the grout.
  7. If formwork is not used, apply suitable repair material such as non-shrinkage, high-strength grout.
  8. The filling process should be in a 15 mm thickness layer if the depth of honeycombing is greater than 5 cm. It is recommended to wait for a while (30min) before applying the next layer.
  9. Repair material strength should match the virgin concrete of the structural element.
  10. Provide texture and color required to match the surrounding concrete and maintain aesthetics.
  11. If present, remove formworks after 12 hours of repair based on the type of material used and ambient conditions. Cure repair material to gain adequate strength.
Pneumatic Gun Used to Shoot Repair Mortar into Honeycombed Areas in Concrete Structures
Fig. 2: Pneumatic Gun Used to Shoot Repair Mortar into Honeycombed Areas in Concrete Structures

FAQs

What is honeycomb in concrete?

Honeycomb is a rough and stony concrete appearance with air spaces between aggregates.

What are the stages of honeycomb repair?

The repair process involves removing loose material, cleaning the affected area, applying suitable repair material, and then curing to gain adequate strength.

What are the causes of honeycomb?

It may be due to improper concrete workability, improper concrete pouring practice, excessive water in the concrete mix, lack of adequate formwork rigidity and waterproofing, etc.

What are the side effects of honeycomb on structures?

The side effects include distortion of structural member appearance and reduced structural strength and durability.

Read More:

Honeycombs in Concrete – Their Causes and Remedies

How to Place, Compact, Cure, and Rectify Defects of Concrete? [PDF]

Injection Grouting: Purpose, Procedure, and Field Considerations

Madeh Izat Hamakareem

Madeh Izat Hamakareem

EDITOR
Madeh is a Structural Engineer who works as Assistant Lecturer in Koya University. He is the author, editor and partner at theconstructor.org.

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