Concrete Cancer is a term used to describe the degradation of concrete structures often caused by interstitial contaminants in the concrete constituents, moisture ingress and the alkali-silica reaction.
Chloride contaminated constituents can find their way into concrete structures if sourced from a chloride rich environment such as a coastal region. Chloride ingress can also be attributed to the structure’s surrounding environment, which is a particularly important issue in Australia. The presence of free chloride ions in a reinforced concrete structure causes depassivation of the steel reinforcement bars, allowing them to corrode. As the steel corrodes inside the structure, the reinforcement bars expand, inducing a stress on the surrounding concrete leading to spalling and concrete failure. Once initial cracks form in the spalling processes, further degradation is accelerated as there is a greater exposure to moisture ingress.
In the alkali-silica reaction, certain concrete constituents in the aggregate react with the alkali to form alkali-silica. This highly hygroscopic compound imbibes moisture from surrounding pores in the concrete structure. This has the effect of creating localised expansion in the alkali-silica rich sites resulting in high internal localised stresses. When concrete has become damaged by the alkali-silica reaction it can produce a characteristic cracking pattern on the surface with white alkali-silica gel emanating from this network of cracks.
Concrete cancer moderate damage at the Gold Coast Queensland
Gold Coast balcony under serious concrete cancer attack
Radar scanning to detect areas of concrete cancer showing area of early attack in the centre.
Concrete cancer 3D image showing balcony is not under attack