The Four Most Common Types of Concrete Damage
ALKALI-SILICA REACTION
In most cases, the aggregate inside of the concrete is more or less chemically inert. Sometimes, the aggregates will react with the alkali hydroxides in concrete which can cause deterioration of the concrete, such as spalling, cracking, or breakage. In ASR, the reactive aggregate contains silica materials, which increase the reaction with the alkali hydroxides. This increase in reaction creates a gel like substance that swells as it comes into contact with, and absorbs, water. This gel then expands within the concrete and causes the deterioration from the inside.
This then materializes as map cracking on the surface of the concrete or larger spalls within the concrete. These surface indicators typically appear where the concrete has the most contact with moisture, whether it be a drainage point or standing water.
SURFACE SPALLING
Surface spalling in concrete can have many causes, but the most common cause if expanding concrete from moisture and rusting rebar. When moisture makes its way into the concrete and down to the rebar, the iron oxide that forms around the reinforcement expands the original size of the reinforcement by almost 6 times. This causes there to be pressure put on the surrounding concrete, which can cause upwards cracks that result in surface spalling.
The spalling of the concrete opens it up for more moisture to penetrate, going deeper than the original moisture penetration. This then causes more deterioration of the concrete, which causes larger, more aggressive spalls and cracks.
INTERNAL REBAR CORROSION
Internal rebar corrosion is when the reinforcement elements inside of the concrete are exposed to moisture that penetrates porous concrete. When exposed to this moisture the rebar develops iron oxide (rust) which makes the rebar grow by up to 6 times. This expansion of the rebar can attribute to many deterioration types, such as cracking, spalling, and much more.
CONCRETE CRACKING
Concrete cracking can be caused by several factors. Rapid drying of the concrete, improper mix ratios, lack of reinforcement, and excess pressure can all be causes of concrete cracking. The important aspect of concrete cracking is determining if the crack is structural, surface, cosmetic, etc. This will determine what kind of solution is needed.