Concrete problems include disintegration, scaling, cracking, efflorescence, erosion, spalling, and popouts. Disintegration is the progressive loss of cohesion of the cement paste within the stone resulting in an increase of its surface area. This causes the mortar to become more vulnerable to chemical attack from water and oxygen in air. Scaling is the deposition of calcium carbonate or other compounds from the concrete mixture onto its surrounding areas - including the hairline cracks that hold it together- causing them to appear larger. Cracking is the development of a series of shallow holes in the concrete caused by either moisture or ice developing inside the slab. Efflorescence is the visible appearance on the concrete surface of any material that has evaporated into solution within the concrete, for example sodium or magnesium hydroxide from the cement. This may cause staining of the concrete or even raise a small puff of dust.
The most common concrete problem involves water entering the concrete structure. This may come from within the building (such as through cracked walls or floors) or without (such as from heavy rain or melted snow). The water enters the concrete, increases in volume, and creates tension within the material that will eventually result in a crack opening up within the slab. This is called "hydration".
Concrete failure can be caused by exposure to harsh weather, reactivity to common components, and faulty construction. Michael Brainerd, principal at Boston-based Simpson Gumpertz & Heger, discusses five typical ways concrete may fail and how to avoid them.
Exposure to Weather: Concrete is a porous material that will absorb water if it is not covered. If it gets wet, it will also quickly dry out. So, if you cannot protect it from the weather, such as outdoor lighting or heating units, then it should be protected with a waterproofing membrane or shield.
Reactivity to Components: Certain chemicals found in some materials used in building projects can cause concrete to crack or split. For example, sulfur added to asphalt for road construction will oxidize and cause sulfate salts to form in the cement paste. This process called "sulfation" reduces the strength of the concrete.
Faulty Construction: Concrete is a product, like any other manufactured item, and like any other product it can be defective when it is made or during its lifetime. For example, concrete that is too soft or weak will wear away more rapidly than hard concrete; this is called "brittleness." Concrete that is too stiff or strong will not be flexible enough to accommodate changes in temperature and humidity, which can lead to cracking.
What Can Go Wrong When It Comes to Concrete?
Concrete deterioration can be caused by a variety of factors. Fire, aggregate expansion, sea water impacts, bacterial corrosion, calcium leaching, physical damage, and chemical degradation can all cause damage to concrete (from carbonatation, chlorides, sulfates, and non-distilled water). Aggregate exposure to heat or air changes the chemical composition of the cement paste, causing it to lose its plasticity. Physical damage can come in the form of drilling holes in the concrete for plumbing or electrical work, or carving words into it with a knife. Chemical degradation occurs when chemicals used in manufacturing processes or improper cleaning products damage the concrete.
Concrete that is not maintained will deteriorate over time. Regular inspections should be conducted to identify problems before they become serious enough to require repair. If you notice any cracks in your concrete, have any metal inserts exposed, or see loose pieces of concrete, call a concrete professional right away to prevent further damage.
Noxious substances and very undesirable components Adverse impacts of harmful compounds on concrete include increased water consumption, decreased binding strength between cement and aggregate, decreased durability, resulting in concrete popouts, and decreased wear resistance. Some examples of harmful compounds found in the environment that can impact concrete include sulfur dioxide (SO2), nitrogen oxides (NOx), arsenic compounds, cyanide, and petroleum products. Concrete that has been exposed to these types of chemicals will need to be cleaned before it is used again for another purpose.