Salt Eats Concrete
Salt Eats Concrete… Reactive Silicates Stop the Damage.
Salt eats concrete for breakfast, lunch, and dinner.
Salt damage is most commonly due to exposure to de-icing salts. However, any chemical containing chlorides, including:
- sodium chloride,
- potassium chloride,
- calcium chloride etc. (all of these can be found in “safe de-icing chemicals”)
- ocean water, etc.
present a danger to the concrete. All are mildly acidic, and attack the bonds that hold concrete together.While the exact mechanism of salt damage is not known, a number of known, related factors instigated by exposure to salt contribute to the deterioration of concrete.
First, salt, a mild acid, lowers the pH in the concrete. The acidic reaction attacks the concrete paste and aggregate, increasing the pore size and allowing additional water and chemicals into the concrete which can exacerbate the freeze/thaw cycle damage.
Second, salt accelerates the carbonation process. Carbonation is a process that slowly reduces the pH levels in concrete and contributes to the corrosion of reinforcing steel. Most salts are neutral to mildly acidic (pH of 4.5 – 7), and absorption of the salts (brine) by the concrete will start to lower the pH of the concrete.
Third, salts are the primary source of chlorides introduced into concrete. Chlorides are also a major player in the corrosion of reinforcement, as they pierce the thin, protective iron oxide layer surrounding the reinforcement and initiate a corrosive reaction in the steel.
Sulfate Attacks from without and within.
Sulfates are, quite simply, a salt of sulfuric acid. They are found in all natural waters, and are a major dissolved component of rain.
Concrete is exposed to sulfates in two ways, externally sourced and internally sourced.
Most commonly, sulfate attack occurs where concrete is exposed to a high sulfate content in the soil, in areas of run-off, and in wastewater.
Secondly, portland cement contains a small percentage of gypsum (calcium sulfate dihydrate). The sulfate in the portland cement is an internal source, and is activated when the internal temperature of the curing concrete reaches 160 degrees fahrenheit, a condition which can and should be avoided.
Sulfates react in the alkaline environment of the concrete paste and create highly expansive crystals called Ettringites. Ettringite is calcium aluminum sulfate. Aluminum is also frequently found as a component of portland cement in trace amounts. The formation of these expansive crystals create a great deal of pressure inside the concrete and cause the concrete to crack and spall.
In addition, sulfates are acidic, break down the alkaline environment in the concrete and deteriorate the concrete paste through acidic attack. This acidic reaction causes the concrete to weaken and crumble.
Reactive Silicates are the best answer to stop these attacks.
Reactive silicates have been demonstrated to nearly completely inhibit water penetration and chloride ion infiltration, significantly reduce carbonation due to their high pH, and provide excellent protection from acidic attacks including salts and sulfates. These products are highly effective at preventing freeze/thaw damage, and do not have any negative impact on air-entrained concrete.
In addition, since reactive silicates use the free calcium in the concrete, they are excellent products for the reduction/elimination of efflorescence. The use of the free calcium/lime and the ability of the products to severely limit water penetration also provide a great deal of protection against Alkali-Aggregate Reaction. Sufficient testing against all reactive aggregates has not been performed, but the anecdotal evidence suggests that these products will be effective against AAR.
A unique characteristic of reactive silicates is that, as they penetrate the pore structure, they raise the pH of the concrete and can force residual salts and other impurities to the surface of the concrete. This has the effect of arresting the damage occurring in the concrete, which gives them a distinct advantage over other products. While it won’t repair large voids caused by either poor placement or acidic deterioration and won’t stop corrosion that is already in the propagation phase, it will have an extremely positive effect on sound concrete, even if deterioration has been initiated.
CreteDefender P2 is this type of formulation… A reactive silicate permanent concrete sealer that can extend the useful life of your concrete and make it impervious to freeze thaw damage, salt damage, protect againnst sulfate attack and chloride penetration… Call or email us to find out how CreteDefender products can make your business dollar go farther and keep your assets looking sharp longer!