How to Fix Honeycomb in Concrete Structures?

Honeycomb in concrete structures caused due to lack of compaction, reinforcement congestion and leakage of grout through the formwork, etc. This issue in concrete structures is discoverable and is observed on the surface of the concrete as shown in the figure-1 below. 

Honeycomb defects in hardened concrete can be minor or major that require different repair techniques. The repair of a honeycomb is an art that demands much care and technical assistance.

Based on the size of the honeycomb size, it can be classified into minor and major honeycombs.

How to Fix Minor Honeycomb in Concrete Structures?

Minor honeycomb can be fixed using approved construction grouts. Usually, grouts are applied after applying a bonding agent and anticorrosive agent as per the specification. But, for small honeycombs, anticorrosive agents need not be applied. 

Figure-1: Minor Honeycombs
Image Credits:saberconcrete.com

How to Fix Major Honeycomb in Concrete Structures?

When the size of the honeycomb is large, special attention is necessary during the rectification. The steps involved in the rectification process are:

1. If the honeycomb is observed in major structural elements that take heavy loads, for example, a column over which many floors are already been constructed; Then special and additional supports need to be provided if necessary as guided by the structural engineer.                                                      

2. 

   Figure-2: Major Honeycomb Observed in Shear wall
   Image Credits: http://www.mobileenterprises.com/
   
   

3. Start removing the loose material from the surface until the concrete is exposed. Brush it till the extent of the honeycombs or the cavities is visible. This can be performed by removing all the loose material.                                                                                 

   Note * Perform all the rectification process manually without using any machineries. As use of machines can result in development of cracks.     

   Light chipping hammers can be used with utmost care to remove the loose concrete. The fractured surface can be removed by sandblasting or water blasting methods.

   Also Read: What are Concrete Cracks? How does It Cause? 

4. The arrangement of formwork for the affected area of the concrete structure is provided based on the shape of the honeycomb.
5. As mentioned earlier, we make use of construction grouts to fill these honeycombs in concrete structures. The mix proportions and mixing are followed based on the manufacturer's guide. So keep in mind to make use of quality grout.
6. For minor honeycombs, no aggregate needs to be added to the grout. But, if the honeycomb is larger i.e. larger than 10 cm, then aggregates must be used. Metal chips can be used, and generally, a 1:1 proportion is followed. Another suitable mix is 1 part portland cement, and 4 parts sand with a water-cement ratio of 0.35.
7. Before applying grout, apply an anti-corrosive agent for the reinforcement to ensure additional protection.
8. A bonding agent can be applied on the concrete surface before adding the grout. The time frame for doing this is specified by the manufacturer of the bonding agent.

When the depth of the honeycomb is large, the process is performed in two stages. There is a maximum depth that can be filled in one stage. Generally, 15 mm thickness is followed for the first layer, followed by 30 minutes resting period before the next layer. After the whole process, the curing process (12 hours) is followed by the engineer or the manufacturer of the grout.

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