Rock Salt, Calcium Chloride or Sand? Choosing Ice Melt for NJ Concrete, Pavers and Plants

Check the temperature first, then the surface.

Every de-icer has a temperature floor. The University of Minnesota's LTAP program, summarizing Clear Roads research, says sodium chloride loses its de-icing power as temperatures drop, that most road agencies consider blending in other products below about 20 degrees F, and that adding more salt in those conditions may be ineffective and wasteful.

Iowa State Extension says to apply enough to loosen ice and snow so it can be shoveled off, because melting it completely takes much higher rates. Penn State Extension says to clear as much as you can before spreading anything, keep grains roughly 3 inches apart, and sweep up the extra so it can be used again. A walk that looks lightly dusted is the target, not a white crust.

Working temperatures below are Iowa State Extension's unless noted. Other sources differ by a few degrees, so treat each as approximate and read the bag.

Each spring, driveways and walks show flaking and pock marks that were not there in the fall. That damage is scaling, and an information sheet from the Pennsylvania Aggregates and Concrete Association, which lists Portland Cement Association and American Concrete Institute references, says de-icers can start it and make it worse. The same sheet says de-icers should not be used on concrete less than one year old.

For older concrete, it says sodium chloride and calcium chloride products are generally considered acceptable on good-quality dense concrete. Magnesium chloride, potassium chloride, CMA, urea, ammonium sulfate and nitrogen salts have been shown to cause much higher rates of deterioration, and ammonium sulfate and ammonium nitrate are aggressive enough to easily destroy a concrete surface.

The sources split on calcium chloride. A 2013 literature review prepared for the Utah Department of Transportation by Brigham Young University, cited by the paver industry, found only minor effects from sodium chloride but significant deterioration, including scaling and cracking, in concrete exposed to calcium chloride, magnesium chloride or CMA. Rock salt is the only product both concrete sources clear for older concrete without reservation, and how much you spread matters more than which bag you buy.

If a slab went in this fall, ask the contractor about the mix. The sheet says concrete facing winter should be at least 4,000 psi, with a maximum water-to-cementitious ratio of 0.45 and 5 to 7 percent air entrainment, and that silane or siloxane penetrating sealers give the highest resistance to de-icers. It also warns that bags printed with 'safe' in large letters often list conditions of use in the fine print on the back.

David Smith, technical director of the Interlocking Concrete Pavement Institute, wrote in 2018 that a paver's density limits how much de-icer gets in, but that ice forming and expanding inside a paver can stress it, and de-icer mixed into that ice adds to the damage. Citing the Utah review, he says to use rock salt whenever possible and calcium chloride judiciously, only when a quicker-acting product is needed.

His other advice: follow the recommended dose, do not use de-icer in place of snow removal, and clear loosened snow, ice and excess salt promptly by plow or shovel. Apply sand first for traction and de-icer afterward as needed, except on permeable interlocking pavers, where sand should not go down at all. The jointing sand the institute recommends limits water entering the pavers and helps keep salts out of the joints. Plow edges are a separate hazard, covered in the driveway markers and plow damage guide.

For Belgian block, flagstone and other natural stone, follow the supplier's written instructions.

A Rutgers Cooperative Extension excerpt from its Plant & Pest Advisory, compiled by Arnold Mercer, says salt in the root zone makes it hard for roots to absorb water, that the sodium in rock salt displaces soil nutrients such as potassium and phosphorus, and that chloride builds up in leaves and twigs until they burn and die back. Sensitive plants show stunted leaves, leaf scorch, early leaf drop and twig and branch dieback.

Grasses adapt fairly readily to high salt levels, the excerpt says, woody plants vary by species, and conifers suffer more easily because they keep their needles. Iowa State names sugar maple, American linden, Canadian hemlock and eastern white pine as salt-sensitive, and notes spray damage on evergreens is worst on the side nearest the road. Rutgers lists American holly, eastern red cedar, white cedar and Colorado blue spruce among salt-resistant evergreen trees, and inkberry holly and junipers among shrubs.

The fixes are mostly placement. Penn State says to keep rock salt 5 to 10 feet from salt-sensitive plants, and Iowa State says not to pile salty snow around trees and shrubs. Rutgers suggests screens where spray reaches plants and leaching salty soil with fresh water as soon as possible; Iowa State adds a heavy watering where salt built up once the ground thaws.

The ASPCA's guidance, dated December 4, 2018, says pets do not typically eat ice melt on purpose; exposure usually comes from licking their feet after walking through a treated area or eating treated snow. Stomach upset, vomiting and diarrhea are the usual results. Eating too much can raise sodium levels enough to cause tremors and seizures, and calcium chloride products can also cause mouth ulcers.

The ASPCA says pet-friendly ice melts typically contain urea or magnesium chloride and can still upset the stomach. That collides with the concrete advice: urea and magnesium chloride are among the ingredients linked to much faster concrete deterioration, and Ohio State says urea works only to about 21 degrees F. A pet label tells you about the dog, not the driveway.

The ASPCA's advice is to wipe paws with a damp cloth or baby wipes as soon as the dog comes in, not to let dogs eat salt or snow (slushy snow especially), use paw wax or booties on cracked or sensitive pads, and store containers out of reach. If a pet has eaten some or shows symptoms, call a veterinarian or ASPCA Animal Poison Control at (888) 426-4435.

Shovel first, spread thin, and use sand when you need grip rather than melting. Iowa State notes abrasives do not melt ice and do not harm plants, and Penn State lists sand for small or thin patches of ice.

If you hire the walk and driveway out, ask which product goes on which surface, and whether that changes for new concrete, pavers and planted beds. How a season plan or a single storm call works is on our snow removal page, and the stream and watershed findings behind using less salt are on the commercial snow removal page. How many snow days a typical winter brings, and how much that swings from year to year, is in the North Jersey snowfall averages guide.

Roof ice is a different job. Pavement de-icer does not fix an ice dam at the eave; the ice dam removal page explains what does.

Every specific temperature, recommendation and caution above comes from one of these.