WATER ENTERING CONCRETE CRACKS AND SPALLING CONCRETE

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11 March 2022 - 9:54, by , in concrete repair, No comments
Once water enters a crack, it is usually only a matter of time before the water leads to oxidization of the rebar/reinforcing steel.

 

Concrete steps can crack and break up over time. Thermal changes and exposure to rain and driving wind can lead to water ingress through cracks in the stairs. For water, it is a simple task to pass through something as small a hairline crack and water has a way of seeking out the passage of least resistance.

In addition to being unsightly, this damage can sometimes lead to unsafe conditions. If parts break off it can pose a risk of injury to people walking by and damage to other property, so it is important to repair your concrete steps before the damage gets too extensive.

 

Cracked concrete, blistering concrete render, breached protective coatings and waterproofing defects often invites water entering the structure, which leads to concrete spalling, rusting reinforcement steel and concrete deterioration if they are left untreated. The corrosion of reinforcement steel leads to reduced resistance of the steel bars, which depending on severity, may negatively affect the load-bearing capacity and service life of the concrete.

Concrete cancer is rust originating deep within the concrete – specifically within the reinforcing steel. As steel rusts, it can expand up to 7 times its original size causing the surrounding concrete to be displaced. The problem is very likely to be much more extensive than what is apparent on the concrete surface. The cancer will likely have spread along the reinforcing in each direction. It is impossible to know the extent until the concrete is chiselled away.

 

SIGNS TO LOOK OUT FOR:

 

  • Cracks and reddish/brown rust stains adjacent to the cracked concrete
  • Rust stains leaking out of the concrete
  • Flaking, spalling concrete
  • Bubbling, blistering, plating of concrete render
  • Leaks in overhead concrete surfaces
  • Rusting, exposed reinforcement steel pushing concrete to become loose and break away from the rebar.
  • Other cracks with signs of moisture seeping through the concrete are potential problems.
  • Look out for cracks showing white crystals or efflorescence. As soon as you see the symptoms such as a crack, seepage or a small rust stain, it is best to get an expert in to carry out an assessment.

THE TYPICAL METHOD OF CONCRETE CANCER REPAIR FOLLOWS A PROCESS OF:

 

  1. Break out unsound concrete and expose reinforcing steel until sound concrete and clean non-corroded steel reinforcing are found.
  2. Saw cut repair zone perimeter to eliminate feather edges.
  3. The concrete around the reinforcing steel is chiselled away. Prepare substrates including removing any corrosion. Reinstate steel and/or add more as deemed necessary.
  4. After completion of material removal, concrete primers and rust inhibitor to the steel are applied prior to reinstating with a high build shrinkage compensated repair mortar. Formwork may be erected to close the cavity prior to installing the repair products.
  5. For further long-term protection, we also recommend a membrane coating system. Install a heavy-duty modified acrylic membrane in multiple layers as a moisture barrier primer system. The primer system will assist in preventing bubbling or blistering, which is highly likely if the remedial waterproofing application is not performed, which could otherwise affect the durability of the system. Our recommendation is that treatment of concrete cancer should incorporate proper weather/waterproofing membrane or it risks being a temporary solution.
  6. The membrane system is detailed to all penetrations and junctions. The system will be supported by the manufacturer warranty for 10 years and extendable for a further 10 years with a maintenance application.

Concrete cracks can also be repaired using a technique called crack injection where suitable epoxy or polyurethane resins are injected.

 

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