Date: January 15, 2016

News - Watch Out For Chlorides - How Salt Damages Concrete

Any chemical containing chlorides such as sodium chloride, potassium chloride, or calcium chloride may be safe by other relative terms, but not when it comes to concrete, especially young concrete.

These chemicals are slightly acidic and therefore weaken the paste that holds concrete together by increasing the pore size and allowing water to enter.  Once additional water is allowed to enter, the freeze/thaw cycle is made worse.

Salt is a unique substance that is considered hygroscopic, meaning that it retains water.  When the salt enters the pore structure attracting up to 10% more water, then freezes and thaws, something has got to give and it usually ends up being the concrete surface.  Pop! Goes the surface and spalling is then apparent.

Chlorides also play a big role in corrosion of reinforcing steel as they quickly get through the thin, protective iron oxide layer and then start the corrosive reaction in steel. 

On the plus side, reactive silicates inhibit water penetration, provide protection from acidic components, and do a great job preventing the unsightly effects of freeze/thaw cycles.  A silicate permanent concrete sealer is highly recommended to protect your concrete year in and year out. 

Other news articles from January 2016