What is Honeycombs in Concrete ?
When the surface looks very rough with voids and gaps between concrete and the reinforcement it is called as ‘Honeycombs in Concrete’. It looks very similar like the honeycomb. Honeycombs in concrete are serious problems which not only reduces the strength of concrete but also makes the reinforcement vulnerable.
Causes of Honeycombs in Concrete
- The honeycombs are caused by improper workability of concrete, using stiff concrete which is hard to place.
- Additional water cement ratio than the allowable limit on-site for better workability. The excess amount of water cement ratio will result in separation of aggregates from the mortar.
- Applying excess and improper vibrations to concrete will lead mortar to leak through the formworks and leaves the aggregates to settle down.
- when we pour concrete from a certain height the aggregates and mortar gets separated and settle down partly which causes honeycombs.
- Typical spots like beam to beam or beam to column joints should be taken care while placing concrete because lapping of one or more layers of reinforcements makes the concrete hard to penetrate through them which can cause honeycombs.
- Presence of coarse aggregates using the improper and bigger size of aggregates in concrete makes the smaller particles hard to penetrate through them and leaves the concrete voids.
Also Read : Segregation of Concrete & How to Prevent it
Prevention & Remedies of Honeycombs in Concrete
- For honeycombs in concrete proper advice should be taken from the designer regarding this.
- If that is not possible then affected concrete should be broken partly and treat it with adhesive chemicals and then should be recast.
- Honeycombs as a defect not only reduces the load-bearing capacity of concrete but water finds an easy way to reinforcement rods and rusting and corrosion starts. Corrosion is a process which continues through reinforcement rods even in good concrete, this result in losing grip between rods and concrete which is very dangerous to the safety and life of concrete structures.
- RCC structures have failed within twenty or thirty years of their construction which is less than half of their projected life. Especially no-risk should be taken in case of columns, foundations, beams etc, where breaking and recasting the concrete is the only best way.
- At places of junction of columns and beams, concrete with strictly 20 mm or less aggregates should be used with slightly more water and cement to avoid honeycombs.
- Taping the sides of shuttering from outside with wooden hammer during concreting and vibrating will help minimizing honeycombs to a great extent.
- In case of columns and beams use of thinner needle say 25 mm or less with vibrator at intricate places of concreting will also help in reducing honeycombs.
Also Read : Curing of Concrete | Types of Curing