Concrete honeycomb is becoming a serious issue nowadays. The Concrete make to form various structural elements like Columns, Beams, Foundations, Slabs. Concrete pour in formwork, it starts to flow like water so cavities/voids form when the concrete does not reach all places. It appears like a honey bee nest. If it does not vibrate properly it leaves voids exposing the aggregate. Honeycomb reduce strength. And provide passage for water that corrodes the reinforcement. Honeycombs which are inside the mass of concrete can only be detected by advanced techniques like ultrasonic testing etc.
Cause of Concrete Honeycomb
1- Insufficient compaction to concrete.
2- Less cover to reinforcement bars.
3- Concrete already set before placing.
4- High concrete free fall while pouring
5- More coarse aggregates than designed mix proportions and oversized aggregates.
6- Improper placement of bars at column and beam junction.
7- Addition of more water than designed at the site for achieving workability.
8- Steel congestion not allowing concrete flow to all corners.
Repairing Of Honeycombs In Concrete
1- First, remove the loosened aggregates and concrete particles from the affected surface by using a wire brush and a chipping hammer.
2- Clean the surface thoroughly with a brush to remove finer particles and then wash the surface with water.
3- Let the surface to dry well and apply Chemi-fix glue on the area.
4- Now mix the concrete grout with white cement and add the required amount of water ( as per the specification recommended by the manufacturer).
5- Then pour/paste the mixture in the affected area to fill it completely. In the case of large honeycomb, the concrete mixture should be poured after creating a pocket.
6- Remove the formwork after 12 hours and then cure it well.