What Is Concrete Cancer?

By Daniel Green

As ugly as the term is, it is extremely accurate. Much like the real thing, concrete cancer is the process whereby concrete structures corrode from the inside out. Although, it is one of the last things you want to happen to your slab.

Speaking scientifically, it is an Alkali-Silica Reaction [ASR] as a result of a hygroscopic catalyst. Sure, but what does that mean? It means that somewhere along the line moisture [most probably water] has gotten inside the concrete where it shouldn’t have been part of a catalyst of some description, and begun corroding the concrete from within.

Overall, you can tell there is concrete cancer present due to several obvious symptoms:

• Cracking, scaling, crumbling concrete
• Leaks, expanding joints, bubbling paint, and/or render
• Cracking tiles
• Rust stains

Concrete is exceedingly strong in its tensile nature. As far as flexion goes it’s woefully inadequate. Swelling from inside a concrete structure will create this flexion and it is this that causes cracking, scaling, and crumbling.

How Deep Does My Concrete Cancer Go?

Unfortunately, that depends. There are many factors that determine the depth of damage caused by concrete cancer. The two primary questions are: what has caused the damage? and how long has it been occurring?

The only true way to determine how deep the rot has invaded is with a thorough physical assessment by a professional in the concrete remediation field.

What Do I Do About It?

Again, that depends on your budget, what are you using the structure for, how much concrete cancer affects compliance, and so on. There’s a list of questions that a concrete remediation expert will need answers to:

• What is the purpose of the building?
• Where is the location of cancer in the building, is it structural or aesthetic? Is it necessary to the function of the building?
• Is the building inhabited? Daily, weekly, annually?
• What is the lay of the land around the building? Has this caused cancer or merely added to it?
• How close is the water table and what saline content is it?
• Are there any chemical leaks nearby that may be the catalyst of cancer?
• Is the building close to, or within range of sea or estuarine air or water?
• How long has the cancer been underway?
• Were proper construction practices used? If yes, did the original builder know of the potential issues? If yes, were proper measures taken to avoid concrete cancer?
• What is the intended use of the building for the near, mid, and long-term future?
• Are there any external constraints to remedial works, ie. council regulations, heritage concerns, hazmat disturbance, the structure’s physical location, and orientation in situ?
• Is the building insured and if yes, is it insured against this type of damage?

These are just some of the factors that determine the cost, type, length, and even the possibility of effective concrete cancer repairs. Sometimes repairs are impossible, meaning full building demolition. Only a contractor that specialises in concrete remediation can collect this information and will potentially take a lengthy site evaluation.

Can I Try And Fix My Concrete Cancer?

Of course. First of all, there are some things to consider. One is that there is a threshold on which property owners can repair their own concrete cancer. The cusp is that you can repair your own concrete cancer if:

a] the damage hasn’t affected the compliance of the building

b] the value of the repair doesn’t exceed $20,000.

Additionally, one further thing to remember is that concrete cancer often adheres to the iceberg rule: 90% of issues are below the surface, which means you won’t fully know to understand the damage until you have opened it up. By then you could be in over your head.

What Can You Do To Fix It?

We have several solutions to concrete cancer. It all depends on the aforementioned questions. There are three primary repair methods though.

Cathodic Protection

This is the least invasive approach and is largely for buildings that meet the following criteria:

• Corroded steel reinforcement causes nonstructural concrete cancer
• Short or mid-term building life
• Lower budgetary constraints

This process is where sacrificial anodes are installed. These anodes are made of lesser material, meaning they corrode easier. As the anodes corrode they are sacrificing themselves for the greater structure by rotting first.

Advantages are quick & easy installation, lower cost, and a mostly dust-free installation. Disadvantages are that the anodes may need periodic replacement and that this isn’t usually a permanent fix.

Mechanical Invasion with Polymer Modified Resurfacing

This is the next most invasive approach and is suitable for buildings where:

• Non- and structural cancer, regardless of cause.
• Shallower depth damage.
• Short, mid, or long-term building life.
• Low to mid budgetary constraints.

In this process, mechanical means, ie. jackhammers, concrete cutting saws, and concrete grinding discs remove the offending concrete. The rotten concrete is removed and any steel reinforcement or metal that is at fault is either removed or ground to a bright finish. The metal is then heavily coated with a zinc-rich primer. A waterproofing membrane is installed if required. The raw concrete base is then meticulously cleaned, dried, and finished with a polymer-modified concrete surfacer.

The advantage is that this is a relatively low cost in comparison to more in-depth repairs. Disadvantages are dust and trying to colour-match the surfacer to the original slab.

Mechanical Invasion with Concrete Finishing.

This process is the same as above except it requires deeper excavation. This means it is best used for:

• Cancer in structural members, regardless of cause.
• Deep damage.
• Mid or long-term building life.
• Mid to high budgets.

The only difference between this and the Polymer Surfacer is the depth of the damage that can be repaired and that the repairs can be made with actual concrete. If the damage is comprehensive enough then new steel reinforcement may need to be tied into the existing concrete by drilling and epoxy adhesives. Additionally, if the member undergoing repair is structural, propping and bracing may be required during the remedial process.

Advantages are long service life and the ability to repair structural damage. Cost and repair time are disadvantages.

So, there you have it. Concrete cancer. Like all states of dis-ease, the sooner action is taken the greater chances of a healthy recovery.

For all your concrete cancer remedial works, contact Tom Matanovic on 0407 491 888.

Perfect Remediation and Refurbishment.

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