Under Water Concrete Repairs

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Following are the different methods to repair underwater concrete structures:
  • Surface spalling repair
  • Large-scale repair of underwater structural concrete
  • Preplaced aggregate concrete
  • Injection technique for restoring an underwater concrete structure
  • Guniting or shotcrete method to repair underwater concrete structure
  • Steel sleeve repairing technique of underwater concrete

Surface Spalling Repair of Underwater Concrete Structures

Cover of underwater structural elements can spall off due to accidental damages. The damaged concrete cover must be replaced and repaired to prevent reinforcement corrosion in the future.
Slightly deteriorated regions will turn to more severe and dangerous damages in short time, especially in splash zones. The deteriorated area of underwater structure should be cleared from both marine growth and loose concrete before repairing procedures are began. After that, based on the number of damages, the boundary of the spalled area should be saw-cut to a depth of 1.2-2 cm. In splash zones, cementitious mortar can be used for the damages region and water-tolerant epoxy mortar may be employed in the case of small damage area.
For the large repaired area, formworks might be used to hold the repairing material at its position. This could postpone enhancement work and prevent epoxy coat utilization because if it hardens it would produce a smooth surface and consequently the bond will be weak.

Large Scale Repair of Underwater Concrete Structures

This technique is a suitable option when damages caused by structural overloading, fire, ship impact, or reinforcement corrosion, especially in the splash zone.
In the case where large areas are required to be restored, repair method and material selection are considered important if shrinkage or bleeding lead to leakage path at the top of parent concrete and repair material interface.
When repairing materials have a great thickness, thermal cracking may develop due to a rise of temperature even though surrounding water decline the temperature rise.
Furthermore, repair of reinforcement is frequently needed because of distortion and considerable corrosion of reinforcement.

Procedure of Large Scale Repair of Underwater Concrete

The large-scale repair procedure is usually as follows:
  • Prepare the damaged region
  • Clean reinforcement adequately
  • Determine formwork typed based on the placement method of repairing material
  • Decrease concrete contamination with salts by flushing formwork with a fresh concrete short period before pouring of repair concrete
  • Pumping is used most of the time for placing repair material and it should start at the bottom of the formwork to push water out of the formwork from the bottom.

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