Concrete has enjoyed a reputation as a “set it and forget it” building material since it became popular in the mid-twentieth century. However, concrete definitely is victim to plenty of external influences. Many of those influences can cause serious degradation.
Builders today are realizing that existing concrete structures won’t last forever. Many buildings from the 20th century, and even some built in the last few decades, show significant damage. Let’s look at what these signs are, and the causes for concrete deterioration.
General signs of deterioration
Fortunately, concrete, as well as most paving work, wears its heart on its sleeve. It’s easy to see damage to concrete and find it. On the other hand, it’s rare for the damage to be totally hidden. So here’s what you should look for:
- Cracking: This is the most common type of damage sustained by concrete. Fortunately, cracks are easily visible, and thus easy to treat once spotted. Be aware though, that hairline cracks can become massive over time, as they allow water inside. When that water expands and contracts, you get small cracks becoming bigger and radiating out more fractures.
- Discoloration: A change in the color of the concrete is not a good sign. If the concrete is changing to a brown/reddish color, it means that there are other chemicals in it. Often the change in color is from corrosion from metals or exposure to other outside chemicals.
- Erosion/Disintegration: These two (used interchangeably), are denoted by cracks and crumbling. They are often caused by the freeze thaw cycle, or heavy precipitation.
Specific signs of degradation
Sometimes very specific elements cause concrete to deteriorate. For example cracks can be caused by a huge variety of things, but the specific cracks that look like scales are caused by an alkali-silica reaction. Here is a list of specific types of damage often sustained by concrete.
- Spalling: Spalling is basically when the concrete flakes away. It can be unimportant or extremely serious. Spalling occurs when the concrete is installed poorly in the first place OR when it is under too much structural stress.
- Alkali-Silica reaction: This chemical reaction in the concrete causes a scale-like cracking pattern. The concrete swells outward and in doing so the surface cracks like the surface of a desert drying after the rain. Also called concrete cancer, it can read to serious degradation, and might even require demolition after being untreated for some time.
- Delamination: Caused when the top surface of the concrete (the laminate) separates from the lower levels. It is found by tapping on the concrete, if a hollow sound is made, the concrete is delaminated.
- Scaling: Scaling occurs when the mortar covering concrete begins to wear away. The mortar is an outside protective layer, so when it goes, the aggregate underneath the surface becomes exposed.
- Chemical diffusion: Also called chemical corrosion or penetration, this happens when a chemical is exposed to the concrete and works its way through the layers. This is a common occurrence with solvents and acids. Chemical diffusion causes cracks, divots, and pits.
Causes of the degradation
Now that you know what to look for, let’s take a look at what causes the problems listed above. Looking through the specific causes of concrete degradation will help create some insights on how to avoid them.
Exposure to chemicals
Chemicals exposed to concrete can wreak all sorts of havoc. From erosion to chemical penetration, there are many threats posed by various chemicals to concrete.
Some of the chemicals might come from routine maintenance:
- Antifreeze agents put on pavement in the winter. These include liquid chemical compounds and salt.
- Cleaning agents for concrete.
Many of the chemicals that damage concrete come from tangential outside sources.
- Vehicles leaking oils/other fluids on pavement.
- Concrete in industrial buildings becoming exposed to solvents or other agents used in manufacturing, agriculture, etc.
- Paint or graffiti.
- Accidents and spills.
- Natural solvents. Carbonic acid, acid rain, and other solvents from nature can seep into the ground and damage concrete. This is especially a threat to underground concrete (foundations). Concrete structures at the bases of hills and mountains may have similar exposure.
- Degradation of the reinforcing steel. When the steel that supports concrete starts rusting or dissolving.
Weather – most notably water is probably the number one destroyer of concrete. The freeze-thaw cycle erodes mountains over time. Concrete is not immune. When water freezes, it expands by 9%, according to a Cement.org study (look at page 4). It’s not hard to imagine water getting into small cracks and freezing to break them open further. The problem is degenerative, once water is in your concrete, it can be impossible to get out.
The freeze thaw cycle also effects the ground. The ground sets differently in the warm months than when it is frozen. This setting can crack and break concrete foundations. Weather damage most often is in the form of cracking and potholes.
When the concrete begins to degrade, or the reinforcing steel begins to degrade, it can not take as much stress. This means that structural concrete may no longer be up to the job it was built for once the deterioration begins.
Adding new levels to a building, placing heavy machinery, or building with heavy materials may induce too much stress on concrete, and cause serious damage. Stress can show up in many forms, spalling, scaling, and cracking.
Just about all of the problems and signs of bad concrete can be caused by one other thing as well: improper installation. If the concrete is mixed poorly, sets poorly, or installed poorly, a myriad of issues can arise. The rebar can dissolve, cracking can occur, delamination…the list goes on.
Get your concrete installed right
If you want your asphalt paving, concrete, or cement inspected for issues, don’t hesitate to contact Reliable Paving. We are an experienced paving contractor who can check your concrete for damage, do repairs, and entire new installations. You want your concrete installation to be done right, the first time, so get a service that’s reliable.