Moderate honeycombing

Moderate honeycombing and vertical offset was observed on column no C-4.

Primary causes of voids or honeycombs in reinforced concrete

• Form Leaks - Leaks in the form-work can allow the cement paste to escape out of the form leaving behind only un-bonded aggregate and rock pockets.
• Inadequate Vibration - When the concrete is properly vibrated it acts more like a liquid allowing it to better settle in the form, consolidate around the reinforcement and completely fill the forms. It also helps in releasing any of the air voids in the mix to the surface. Improper vibration can be related to:
  • Too small or large a vibrator for the size of the pour and mix design
  • Too low a frequency or amplitude of the vibrator for the size of the pour and mix design
  • Too short or long an insertion time of the vibrator in the concrete in a single location
  • Too wide of a spacing between each insertion of the vibrator
  • Congested reinforcing that will not allow a standard vibrator to reach all areas required

• Mix Design - Improper mix design can lead to low workability, early stiffening or an aggregate that is too large to properly consolidate the concrete for a given application. A good mix design should take in consideration the issues noted for rebar congestion and lift depth.

• Rebar Congestion - if rebar is placed too close together or too close to formwork it will trap the larger pieces of aggregate while the mortar in the mixture may or may not pass through. Other causes related to rebar congestion include excessive reinforcement splices that prevent the concrete from properly filling the forms.

• Lift Depth - When single concrete placements or "lifts" are too deep, proper vibration can become very difficult or impossible. Excessive lift depths can also allow too much free-fall of the concrete that can create a separation of the cement mortar and aggregate as the aggregate impacts the reinforcing steel when falling through the forms.

Repairing of honeycombing

• Mild and moderate honeycombs shall be repaired using Non-shrink mortar mixed with bonding chemical.
• Curing of repaired patch shall be cured using curing compounds.