Contrary to popular belief, concrete is extremely porous. While it is very hard, it also has millions of tiny pores and microscopic cracks. Looking at concrete under magnification reveals the pore and capillary structure. It is remarkable how many tiny voids there are. There are a number of ways that concrete gets destroyed and damaged but the most common reasons are de-icing salts and freeze/thaw cycles.<
When salt and water get in concretes pores, the breakdown begins. Salt gets carried into the pores of the concrete by water and creates an acidic-like reaction inside the concrete, eating away the bonds in the cement portion of the concrete, and creating larger voids that attract more water and salt. Salt is hydroscopic, which means that it attracts water, up to 10% more water in the same space. Water is the real catalyst of damage. Salt just makes it easier for water to get into the pores and capillaries of concrete.
When water gets absorbed into the pores, it can expand up to 9% when it freezes. This pressure creates cracks and larger voids in the interior structure of the concrete, creating larger pathways for water and chemical intrusion. Sooner or later, the pressure from freezing water will pop the surface of the concrete, exposing the aggregate, and creating an unattractive look and a potential safety issue.
The key to protecting your concrete is to seal with a Ghostshield penetrating concrete sealer like Siloxa-Tek 8500 to permanently prevent salts and water from entering the concrete.