What is Honeycombing of Concrete? Prevention and Repair: 8 Important Points

Table of Contents

What is the Purpose of Cement Concrete in Structure Elements?

What is Honeycombing of Concrete?

What are the reasons for Honeycombing of Concrete?

Following are the key reasons for Honeycombing of Concrete:

The Consequence of Honeycombing of Concrete:

How to Repair Honeycombing of Concrete/ Remedial Works?

What are the Commonly known Grouting Methods?

Permeation grouting

Vacuum Grouting

Jet Grouting 

Compaction Grouting

 Fracture Grouting

How to Eliminate or Mitigate Honeycombing in the first place / Repair Works:

You must have seen the poorly appeared structure surface with exposed reinforcement or aggregates, it is known as Honeycombing of Concrete. Do you know what exactly Honeycombing of Concrete is, why it happened, how to prevent it to happen and how to repair it?

Please read this blog for details

What is the Purpose of Cement Concrete in Structure Elements?

In simple terms, cement concrete is a mix of adhesive (cement) and small grits or aggregates. The adhesive is made from a mix of cement and water in the desired ratio. When added together (cement, water and aggregate), a chemical rejoinder takes place and it hydrates the mix and gradually the mix begins to harden.

Once settles, it increases its strength and becomes a solid mass concrete. The durability and strength of cement concrete is the key driver to consider it as indispensable material for all types of structures such as bridges, buildings, highways, railways, etc.

What is Honeycombing of Concrete?

When cement concrete is dispensed into the structure casing or formwork, the mix flows like a very concentrated liquid. In an ideal situation, it should gradually flow in all directions within the casing or formwork, but sometimes it doesn’t happen. When it doesn’t happen means, when the mix doesn’t reach all the places within the formwork, it creates voids.

Once the concrete settles and formwork is removed, it appears like a nest of the honeybee and as a result, the structure loses its full expected strength.

What are the reasons for Honeycombing of Concrete?

After removing the Formwork, when the settled concrete surface displays small pockets of air void and or exposed aggregate without mortar (cement mix), it is called honeycombing of concrete. Honeycombing could be present on the top surface or it could be present deep inside. 

As a result, it significantly impacts the strength of the structure. Honeycombing of concrete also allows seepage of water through it and as a result, the steel reinforcement begins to corrode, which is a serious risk to the integrity of the structure.

Following are the key reasons for Honeycombing of Concrete:

• Inadequate compaction to the concrete mix.
• Settlement of concrete-mix before full placement within the formwork
• Improper placement of concrete around steel reinforcement
• Inappropriate placement of steel reinforcement within formwork and blockage for water to flow to all the corners.
• Inappropriate use of a vibrator to mix and place concrete within the formwork.
• Poor workmanship.

Read More:

• Why does Concrete need Reinforcement? 6 Important Points
• What is the Function of Bridge Foundation or Pier and its Types? 5 Important Points

The Consequence of Honeycombing of Concrete:

• Poor appearance of the surface finish of the structure
• It worsens the structure's strength and integrity
• Honeycombing makes the concrete mix very weak
• It leads to the corrosion of steel reinforcement
• It provides an easy passage for water to flow within and makes the structure weak.

How to Repair Honeycombing of Concrete/ Remedial Works?

• Clearly identify the affected area and mark it up. Extract out all honeycombed area and aggregate plus concrete mix.
• Apply chemical glue across the cleaned-up area.
• Apply Grout Mix.
• Apply concrete mix across the whole surface and set the formwork
• Remove the formwork after 24 hours.

What are the Commonly known Grouting Methods?

• Permeation Grouting
• Vacuum Grouting
• Jet Grouting
• Compaction Grouting
• Fracture Grouting

Permeation grouting

• Permeation grouting is a well-known and widely used grouting method.
• In this method, all joints, voids and honeycombed areas are filled back with new concrete mix.
• It strengthens the new formation and provides a clean surface to the structure.

Vacuum Grouting

• Vacuum grouting is a very effective method and it places concrete mix very precisely across the surface.
• In this method, concrete is placed under vacuum pressure and if any location is found to create a void (which could result in further honeycombing) again, it extracts out the material by reverse vacuuming.

Jet Grouting 

As the name suggests, Jet grouting means grouting with a high-pressure jet. The jet pressure removes the unwanted material first and then applies grout to the surface.

Compaction Grouting

• In compaction Grouting, the mix is injected through pressure and compacted within the formwork.
• Compacting Grouting is carried out in phases.

 Fracture Grouting

Fracture grouting uses a low viscosity cement grout and injects it under high pressure. In this grouting method, the concrete mix and the chemical mix is injected through hydraulic pressure. Grout is pushed down the casing or formwork and spread over the fractured area.

Read More:

• How to make a successful career as Civil Engineer- 5 Points Mantra

• How to get a job with no experience – 8 secrets

How to Eliminate or Mitigate Honeycombing in the first place / Repair Works:

• Check the Framework is firmly placed. All the steel reinforcements, braces and joints are tightly placed. There are no gaps or openings left within the formwork
• Cement and aggregate are properly mixed and when placing the concrete within the framework, make sure it is compacted adequately and there are no voids left anywhere within the framework.
• Ensure that the mix has flowed in all areas within the formwork and formwork is totally filled.

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