Common causes of concrete cancer and remedies

It’s ugly, it’s pretty hard to stop and chances are, it’s not going to be cheap to fix. It can start with a subtle crack, then you might see signs of rust or discolouration, next, it becomes brittle and if you leave it for too long it could end up costing you a fortune. It isn’t just something that looks horrible either, it can put people in harms way. I’m talking about concrete cancer.

Concrete cancer is the result of moisture mixing with the steel that reinforces the concrete, this causes the steel to expand and the concrete to crack. Contrary to popular belief, concrete cancer is not always caused by poor craftsmanship, there are numerous reasons that contribute to concrete cancer. Below are the most common:

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Concrete Cancer

#1: Poorly poured concrete & insufficient concrete cover.

If the concrete is not sealed properly after it has been poured, water may leak into the concrete and come in contact with the steel that reinforces the slab. Moisture and steel don’t get along, the steel will begin to rust and expand, obviously, as the steel expands the concrete that surrounds the steel begins to crack and displace. In its early stages, it may feel brittle underfoot, cracking as you walk on it or you may see signs of rust and discolouration. It’s not something that stops or stays in one area, it spreads and can start from deep within a slab not just on the surface.

#2: Poor Waterproofing

Waterproofing is the process of making a slab waterproof or water-resistant. It is a control put in place to avoid rain, moisture and leaking into the slab causing concrete cancer and hindering the structural integrity of the building. Poor waterproofing can cause a lot more than concrete cancer such as health risks from the mould, allergies and fungal infections.

#3: Incompatible reinforcing metals used in the slab

When incompatible metals are in contact by an electrolyte such as water (mixed with concrete), an effect called electrolysis occurs. The dissimilar metals then set off a galvanic reaction that causes the weaker metal to corrode. As the corrosion progresses, the reinforcing steel begins to expand. The flow on effect from rusting steel is as above. The steel expands displacing the surrounding concrete, then the concrete cracks and becomes frail. One thing to remember is that the cracking could go into the slab to begin with, and remain undetected for some time. This is why it’s important to have a professional come to inspect your property at the first sign of concrete cancer.

#4: Reinforcing bars too close to the surface

Have you ever poured water on concrete and noticed without any sunlight the water disappears? The water is actually being absorbed into the concrete (like a sponge). Like wood and other materials, as concrete heats up, it expands and as it cools down, it retracts. While the concrete is in an expanded state, moisture or water may seep into the concrete. If the reinforcing steel bars are to close to the surface of the concrete, they are more likely to come in contact with any moisture causing oxidation. Oxidation creates rust, rust causes concrete cancer.

#5: Stress fractures from excessive weight

If a section of a slab has been used to bear an excessive amount of weight but the concrete was not designed for it, a common side effect is stress fractures in this particular area of the slab. When stress fractures occur, there is an open path for water and moisture to flow and sit. If this water is deep enough and comes into contact with the reinforcing steel the concrete is at instant risk of concrete cancer.

Structural/Cosmetic Repairs

Concrete Cancer Remedies

You do not have to be a structural engineer to identify concrete cancer, however, getting the professional opinion of a qualified expert for concrete cancer rectification is certainly recommended. If you suspect you may have any signs showing or issues mentioned above, acting sooner rather than later could save you a small fortune. BRS have many years’ experience in structural and cosmetic concrete repairs giving them the ability to refine the best suitable concrete refurbishment method for each project.