Concrete peeling and concrete cancer are terms used to describe the state in which concrete begins to degrade or chip off. Common signs of this deterioration include cracking, crumbling, peeling, rust stains, bubbles in concrete or cement plaster, and leaks in the ceiling and walls. Chipping is a term used to describe areas of concrete that have cracked and delaminated from the substrate. There are several reasons why chipping occurs, such as freeze-thaw cycles, the expansive effects of the alkaline silica reaction, or exposure to fire.
However, the most common cause of chipping is corrosion of embedded steel reinforcing bars or steel sections. Corrosive steel can expand up to ten times its original volume, putting stress on the surrounding concrete. The consequences of chipping can be serious. If a structure is allowed to deteriorate, its value will decrease and maintenance costs will increase as corrosion and scaling become more widespread.
For some structures, such as car parks, customers may stay away if the environment is unattractive and potentially dangerous. The peeling of concrete, especially on the outside of a building, not only looks terrible but is also potentially hazardous. Over time, and with increased exposure to the elements, untreated pieces of concrete may fall out of the structure and cause damage or injury. Chipping affects a wide variety of structures, including concrete framed buildings, multi-storey car parks, bridges, jetties, tanks and ponds.
The word “chipping” refers to the breaking of a material into pieces, in particular cracks below the surface that cause part of the surface to peel off. The effects of chipping can range from being inconsequential - a purely aesthetic problem - to causing serious structural damage that requires costly remediation work. Appropriate mixing of sand, cement and aggregates must be achieved when pouring concrete as insufficient aggregate can result in a weak and prone top layer to chip. Unfortunately, an adhesive plaster approach is often taken to repair peeling structures without treating the underlying causes.
Beyond the obvious aesthetic problems, a reduction in cross-sectional area due to flaking and delamination weakens the concrete section. If peeling has already occurred, damaged bricks can be replaced but the cause of moisture must also be properly identified and treated. The reason why some concrete structures exhibit widespread flaking while others appear to be in good condition is due to a combination of age, maintenance, concrete quality, concrete cover depth and local environmental conditions. Measures can be taken to prevent flaking when the concrete is first poured as the concrete mix will influence its likelihood of flaking in the future.
And if you have chipping present in your structure it's important to have it treated as soon as possible to maintain its structural integrity.