What is Concrete?..and Why Does it Crack?

What is Concrete?

Foundation Crack

Quite often the terms cement and concrete are used interchangeably, but cement is actually an ingredient of concrete. Cement is made up of limestone, calcium, silicon iron, and aluminum. This mixture is heated to about 2,700 degrees Fahrenheit or 1, 482 degrees Celsius to form a substance called clinkers (looks like marbles). Clinkers are ground to make a powder and then gypsum is added. As a result of this, a powder is formed and this powder is referred to as cement.

Concrete is a mixture of cement, water, sand, gravel or crushed stone.
When you add water to cement and rock mixture a reaction called hydration makes the cement and water harden and it binds the aggregates into a rocklike mass. This hardening process forms concrete and this hardening process continues for years. As a result of this concrete gets stronger as it gets older.

If the Concrete Mixture is so Strong Why Does it Crack?

The main reasons are:

The most frequent cause of cracks in concrete is shrinkage that occurs as the concrete dries. When concrete cures, the water that has been mixed with the cement begins to evaporate and this causes the concrete to shrink a little.

Support Problems
Some of the most severe cracks in concrete are caused by inadequate structural support. This lack of structural support may occur as the soil beneath concrete slab shifts or is eroded by natural elements such as wind and rain. It could also be caused by poor installation such as improper use of rebar or insufficient formwork.

Changes in Temperature
The temperature change can be a major cause of cracks in large concrete applications. This is because of the temperature variations between concrete that are poured first and subsequent layers of concrete. Temperature variations can cause some portions of the slab to expand while others are shrinking and this will lead to cracking.

The Spalling Effect
Spalling is a term given to concrete when it has a rough, flaky surface. Spalling is the result of hundreds of tiny cracks, which usually appear only on the surface of the concrete. Spalling typically occurs when too much water is added to the concrete mixture, or when the surface layer dries faster than interior layers.

If additional strength is required concrete may contain metal reinforcement, this will help increase the strength of concrete.  These reinforcement techniques may include wire mesh, rebar or steel beams. Should these materials begin to rust, the rust will cause an expansion in the concrete. This expansion may cause hairline cracks and small surface cracks. It is also possible that water could infiltrate these cracks and cause even more rust.

Of course, every case is different and if you have cracked concrete that you think is becoming a foundation problem or if you simply have a leaky basement or cracks in basement foundations you should have it reviewed by an expert.

Cracked Foundation Repair

Quite often repairs or solutions are not as expensive as you might think and the repair will be worth the peace of mind. In the following video, the house that is being repaired was getting ready to be sold and the owner wanted the foundation crack repaired properly. It is interesting to note that the foundation wall crack repair warranty is transferrable to the new owner. It doesn’t get much better than that.

If you have a foundation problem and would like to have it reviewed by an expert, call Phil Russell of CrackMaster Concrete 604-614-2615. There is no cost or obligation for this service.