Corrosion Induced Delamination

Corrosion Induced Delamination

What is corrosion induced delamination and how to prevent it?

Corrosion induced delamination, is expanding steel reinforcement in concrete caused by oxidation. Preliminary symptoms are moisture spots, efflorescence and active water leaks. When early symptoms are left untreated, rebar will expanding. Expansion of internal rebar causes cracking and then the loss of concrete cover caused by broken concrete sections. Taking signs of cracking and delamination seriously is very important for the health and safety of building users.

Why does concrete delamination occur?

  • Standing water penetrates the pores of concrete causing high levels of moisture close to the steel leading to freeze/thaw damage.
  • De-icing salts on the slab or from vehicle run-off.
  • Water travels through cracks in the concrete and comes in contact with internal rebar leading to rust.
  • Improper leak repairs trapping water in the substrate. If water is prevented from coming out of the slab, but allowed to sit within the slab the chances of delamination raises drastically.
  • Poor ventilation increases humidity levels and can lead to delamination in concrete ceilings.

How is concrete delamination hazardous?

Delamination’s on the floor create tripping hazards. Ceiling delamination’s are falling object hazards. Falling concrete can lead to vehicle damage or personal injury. Delamination’s indicate the loss of structural strength in a building. Over-reinforced structures can fail catastrophically with little prior notice. When delamination’s occur at a height, it is extremely dangerous due to the velocity of falling objects.

Is concrete delamination preventable?

All concrete is prone to shrinkage cracks and all steel is prone to oxidization. The best way to avoid delamination is to protect concrete using sealers, waterproofing, and by repairing leaks. The cost of concrete repair projects can be reduced when repairs are budgeted for and implemented quickly. The cheapest time to repair your structure is always now. Upon discovery of delamination, planning repairs in the area quickly becomes crucial. Repair costs can grow exponentially. It may take 10-20 years for delamination to occur, but once it does the steel has already expanded past the concretes breaking point.
The quantity of delaminated area increases quickly once delamination’s occur. This is due to the strength loss from missing concrete, and the increased surface area of exposed steel.

If full repair isn’t possible, the next best options are;

  • Remove immediate hazards and protect occupants from harm.
  • Protect exposed rebar, preventing further oxidization.
  • Stop the leaks that are leading to corrosion.
  • Implement controls to reduce moisture and/or water in contact with concrete surfaces.

How to get concrete repair pricing?

A Miller & Co estimator will first determine the project scope through site observation and then chain drag surveys. With the amount of delamination accounted for, project pricing and phasing can commence. A chain drag survey includes marking repairs with paint, which can be used for engaging bids from other contractors or engineers.

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