In southern states, where deicers are not used, the normal ASTM C666 test method would most likely classify these dolomites correctly. However, not many southern states use the ASTM C666 test method for obvious reasons. The effect of ocean mist brine on PCCP may be similar to the effects of deicers. The generation of magnesium sulfate is restricted to pyritic dolomites. Wagon trains, traveling through the state of Iowa, stopped at certain dolomite outcrops to gather magnesium sulfate from the surface of the bedrock.
Magnesium sulfate is extremely soluble in water.
The water in the pore system of the bedrock carries the magnesium sulfate to the surface. The magnesium sulfate is left behind when the water evaporates. The fine to medium grained dolomites usually contain an extensive capillary sized pore system that allows the brine to have access to a very large surface area within aggregate particles. One theory holds that the magnesium ions, in the paste, migrate to magnesium hydroxide sites, making them larger and consequently causing cracking of the paste. Blast furnace slag may or may not contain magnesium, depending on the type of carbonate used in their production.