Concrete Repairs
Spalling concrete or concrete cancer, as it is sometimes referred to, is caused by the corrosion of steel in concrete, this occurs mainly by one of the following procedures.
When concrete is placed it is in an alkaline state. This is the chemical state of the concrete, which acts to protect the steel against corrosion. Through weathering and a process called carbonation and/or chloride ion attack, the alkaline protection diminishes. Due to minor building movement or shrinkage of the concrete when curing or breakdown of protective paint coatings or minimal concrete coverage over steel (or a combination of all four), cracking of the concrete occurs.
The affects of carbonation and the cracks, (which are at times microscopic) allow water and air to reach the reinforcing bars where corrosion or rusting occurs. The product of the corrosion process, rust (ferrous oxide), can have a volume eight times the original volume of steel. The increase in volume exerts considerable forces on the surrounding concrete and as the concrete is weak in tension, it breaks away. As the concrete breaks away it exposes more of the reinforcing bar to the elements and hence, accelerates the deterioration process
Although only a small amount of corrosion is first visible, the extent of the corrosion continues along the reinforcing bar and hence, a lot of the area that requires repair is not visible. Wire ties left in the bottom of the formwork and the bottom of bar chairs can cause minor rust marks. The same corrosion process applies and damage to the building occurs
As can be seen, the more damage that occurs, the faster the deterioration, hence the name, concrete cancer. Unless treated, the problem extends at a more rapid rate. To protect the structure against future corrosion it is important to ensure that the protective coatings placed on the concrete and the concrete repairs are of a very high standard.
To arrange for a representative to come and give you a quote on any of your spalling concrete or concrete cancer needs, please contact us today.