I have a 15 year old concrete drive that is beginning to show poch-marks like little divots. What sort of ice melting product is least damaging to my concrete?
The poch marks are likely from rock salt deterioration on your concrete drive. It can be caused by using rock salt to melt ice on your drive or can be brought onto your drive by parking vehicles on your drive that drive on public roads. The road crews typically and economically treat our roads and highways with rock salt which is highly corrosive to concrete.
Sealing your concrete can delay the concrete deterioration and minimize the ugly popping or poch marks on the concrete. The cleaning and sealing process is typically done with a penetrating sealer and a stain resistant top sealer.
Good Ice melt choices for concrete are Calcium Chloride and Magnesium Chloride. While Potassium Chloride is good for the environment it damages the concrete. These look like little white balls similar in appearance to lawn fertilizer pellets and typically cost 3-5 times more than rock salt. So my recommendation is to use Calcium Choloride and Magnesium Chloride.
Another good de-icer is CMA or Calcium Magnesium Acetate which doesn’t wash away as easily as the others and is a lower environmental impact. Normal bacteria will eat CMA so Mother Nature will clean up and control CMA contamination. These products undergo a chemical reaction that produces heat when they get wet, which controls the ice. These de-icers work at colder temperatures down below zero F, with rock salt and Potassium Chloride losing effectiveness at about 20 degrees F.
CMA, Calcium Chloride and Magnesium Chloride are most effective with CMA being the longest lasting. Potassium Chloride and salt work at warmer temperatures above 20 degrees.
Avoid using rock salt for concrete de-icing because it is highly corrosive to concrete and damages the surface by popping the weakest spots off the surface. Water expands as it freezes into ice inside your porous concrete and pushes or pops the small surface craters off the top of the concrete pavement. All de-icers are best applied just before the snow falls to coat the drive surface and minimize the ice buildup. These de-icers can leave an oily residue that can be hard to clean up after the cold season. Asphalt drives can be de-iced with common rock salt because it does not corrode the oil based asphalt material but rock salt is can damage or kill vegetation.