What is honeycomb in concrete?

Honeycomb in concrete is a term for spaces or cavities in concrete. Industrial Structural Consultants play a crucial role by ensuring no concrete honeycombs. This can be done by putting proper SOP in the tenders. This happens as a result of improper concrete filling inside the formwork.  Honeycomb in concrete leads to cracks, failure of the concrete, and reinforcement corrosion over time.

What are the causes of honeycomb?

• Vibration: Proper vibration is crucial during concrete placement to avoid air voids. 
• Design Mix: Honeycombing can also be due to improper concrete mixtures with improper aggregate gradation or inadequate workability. Excessively large aggregates also cause voids in the concrete. Honeycomb could be a result of stiff concrete or placing of already set concrete
• Defective formwork: Loose or leaking formwork permits seepage of grout and flow out. 
• Curing: Curing is essential to avoid honeycomb. If concrete is improperly cured, cracks and voids develop. 
• Inadequate compaction: Insufficient compaction results in air voids trapped in between during concrete pours. 
• Improper placement of steel reinforcement: The spacing of reinforcement bars is essential, and inappropriate placement may obstruct concrete flow. 
• Concrete Pour: Dropping concrete from a height also affects the concrete and may result in honeycombing.

Types of Honeycomb in Concrete

Honeycombs in concrete can are of the following categories based on their size:

• Small honeycombs: The voids are less than 10mm in size. These honeycombs are due to minor voids or surface irregularities. They may not be of a structural concern. It, however, affects the aesthetics of the structure.  
• Medium-sized honeycombs: These range from 10 to 50mm in size. The reason for medium-sized honeycombs is improper vibration or poor formwork. These honeycombs reduce the concrete strength and durability. It needs remedial action.
• Large honeycombs: These are greater than 50mm. Such honeycombs result from poor formwork, improper placing, and improper compaction. Failure to clean the formwork of debris before concrete also results in large honeycombs. The concrete’s structural integrity is compromised.  

How to prevent honeycomb in concrete?

Structural consultants include the following in the standard operating procedures in the tender to avoid honeycombs:

1. The deployment of chutes deployed during concrete, especially if the height of the drop is above 1.50 meters.  
2. The contractor must check the concrete’s workability before pouring.
3. The consultants must approve the design mix to ensure the correct aggregate size.  
4. Formwork: Clean, well-oiled formwork is essential for well-placed concrete.
5. Reinforcement placement must be adequate to ensure proper concrete filling inside the formwork.

How does honeycomb impact the concrete?

Honeycomb impacts the concrete in the following ways:

1. Reduction in concrete strength
2. More permeable
3. Compromises the aesthetics
4. Safety hazards.

Conclusion

The structural consultants have an essential role while preparing the civil tender. This ensures that the SOP issued by the industrial structural consultants is as per the standards and thus, avoid concrete honeycombs.