Chipping of concrete is a common problem that occurs when water trapped in the concrete goes through multiple freeze-thaw cycles. When water freezes, it expands by about 9%, which creates tremendous pressure inside the slab. This pressure causes microcracks to form, and the surface begins to separate from the body of the slab. Another cause of chipping is carbonation, a natural process that occurs when water seeps into the concrete and corrodes elements such as reinforcing bars embedded in the concrete.
This corrosion leads to bulges and cracks on the surface of the concrete. Poor quality steel can also lead to chipping. Sealants are a great way to protect concrete from chipping deterioration. A good quality sealant designed for outdoor use will help minimize water saturation and protect against salt damage.
However, even with a good sealant, concrete itself is still the most important factor in preventing flaking. In most cases, peeling concrete is caused by poor finishing and the use of too much water during the finishing process. Excess water and overfinishing create a weak surface that cannot withstand freeze-thaw expansion and contraction. Alkalinity, a normal corrosion mechanism, causes steel bars inserted into concrete to corrode over time.
Concrete peeling is also caused by environmental factors, poor installation, and other reasons. While sealing it will not completely prevent peeling, it will help decrease the chances of it occurring. To fix chipping, you may need to re-coat the doorway with a layer or repair it with grinding. Rainwater or water from any other external source enters the capillaries of the concrete first.
De-icing chemicals only aggravate already stressed concrete by allowing more water to migrate into it, increasing the size and depth of husking failures when freezing occurs. Signs of chipping include a chipped and scaly surface, pieces of concrete coming out of the facility, and concrete that begins to crack. The protection afforded by high alkalinity can be compromised by acidic atmospheric gases (carbonation) or by salts in concrete from marine environments or de-icing salts. The location of the concrete structure, type and other related factors are also considered when assessing chipping risk. Chipping can have far-reaching consequences in terms of health and safety, structural integrity and asset value. It only takes two to four hours to dry and creates an invisible glass-like barrier deep in the pores of the concrete.
However, despite best intentions, concrete patch repairs often fail prematurely due to ongoing corrosion around the periphery of repairs.