Tag: cacl2

Post #2086: Disbondment, my next road salt lesson.

 

The big boys — VDOT and its road-plowing bretheren — they salt the pavement when it snows.

So, why can’t I do the same, with my driveway?

Turns out, the reason VDOT salts the roadway is completely different from the reason I salted my driveway.

Huh.  Maybe you knew that, but I sure didn’t.

And as a corollary, recommended salt spreading rates for salting roadways have nothing to do with the amount of salt I needed melt the snow off my driveway.

Let’s not belabor this.

VDOT clears snow off the roads by plowing the snow off.  Their goal is to plow down to bare pavement when possible.  But they can’t do that if the snow and ice is stuck fast to the pavement.  VDOT uses salt to keep snow/slush/ice from adhering to the roadway.

Hence, disbondment.  The act of taking ice and snow that are frozen hard to the underlying pavement, and getting them loose.  Dis-bonding them from the underlying pavement.

Typically, VDOT’s goal is to use salt to melt just the very bottom layer of the snow/ice pack, where that touches the pavement.  They want to weaken that interface, so that the snow/ice can be scraped off with a normal snowplow.

I, by contrast, was using salt to clear the pavement.  That is, I wanted to melt the entire predicted thickness of the coming snowfall.  That, because I specifically didn’t want to scrape the snow and ice off the pavement.  I wanted them to run off, as salty water.  (I admit that I was right tired of shoveling, at this point in our most recent winter storms.)

Guess what?  If you’re only trying to melt that very thin interface between snowpack and pavement, a) you’re happy to use snow-melt pellets that just melt a little hole in the snow, until they get down to pavement, and b) overall, disbonding-then-plowing uses a lot less salt than melting the full thickness of the snow pack with salt.

A typical manufacturer recommendation for home use of de-icers (e.g., rock salt, calcium chloride pellets) works out to around one 50-pound bag of salt for every 1000 square feet.  Whereas the (reportedly) most common recommended rate for VDOT salting the road is about five pound per 1000 square feet.

 

Conclusion

There are a few fairly big conclusions, from the simple observation that VDOT’s use of salt and my use of salt are not at all the same.

First, just because VDOT salts the roads doesn’t mean I have an excuse to do it.  If for no other reason, what VDOT is trying to do with salt (disbondment of snow/pavement interface) has nothing what I’m trying to do (melt the entire thickness of the falling snow).

Second, you can’t take recommended salt spreading rates for road use, and apply those to melt the snow off your driveway.  It’s not nearly enough salt.  You will end up committing homeopathic ice melting, as described two posts back.

Third, using salt to melt snow in bulk — say, the full thickness of a light snowfall, off my driveway — that may be a remarkably stupid thing to do.  Again, per square foot, it takes vastly more salt to do that, than it does to treat the roadways.

While my road salt is but a minor contributor to the problems caused by society’s reliance on road salt, there’s no point in my adding fuel to the fire, needlessly.  Maybe in some climates, some locations, you absolutely have no choice but to use road salt on your driveway and walkways.  But Virginia, USDA Zone 7B, ain’t one of them.

I may take one more stab at this topic, trying to assess environmental safety of various road salts/ice melters.

And I may not.  Environmentally, the best choice is to use nothing.  So I’m not really feeling compelled to suss out various road salts’ claims of environmental friendliness or minimal impact on machinery and the built environment.

I may be done with salt.

Post #2085: The mess that is the ice-melt market, in one phrase: Pet-safer.

 

I am still trying to get up to speed on ice-melting compounds.  So far, two things appear crystal clear.

First, rock salt — sodium chloride, NaCl, halite — is the worst ice-melting compound, in terms of metal and concrete damage, environmental harm, and pet safety.

Second, most of the claims, made by most ice melters, are, at best, exaggerations.

Pet-safer:  Crossing the line on exaggerated product claims.

But some ice-melter claims — particularly regarding “pet-safe” and “eco-friendly” — are purposefully deceptive.

And, oddly enough, those purposefully-deceptive claims of “pet-safe” and “eco-friendly” ice melts work exactly the same way.  In order to be legal, they only claim to be pet-safer or eco-friendlier.  Than what, you might ask?  Than pure rock salt.  So the first takeaway is that anything that’s even trivially better than pure rock salt — such as rock salt with some tiny amount of additives — can advertise itself as both “pet-safer” and “eco-friendlier” (…. than rock salt).

Surely we agree that rock salt is not pet safe?

By way of making this as clear as possible, let me narrow it to dogs.  And focus on the bottom of the barrel — rock salt.

A dog will get sick if it ingests too much (table, NaCl) salt.  One reference listed a dog-lethal dose of sodium chloride (salt) as 4 grams per kilogram body weight (Source:  Veterinary Toxicology, 4th Edition.)  Thus a 30-pound dog that manages to eat two ounces of rock salt, and keep it down, might reasonably die from doing that.  (That’s about three level tablespoons of table salt.)

And a dog could pretty clearly get sick from a lower dose than that.  Salt poisoning leads to vomiting, diarrhea, and, if it proceeds far enough, to neurological symptoms (e.g., inability to walk).

Salt poisoning of dogs does not appear to be very common.  Another reference said that in 1998, there were just 50 such cases reported to ASPCA poison control hot line.  Currently, salt poisoning doesn’t make the top 10 list of common pet poisons.

And, from reading a few case reports, ice-melt poisoning can occur if a dog takes a big gulp of the stuff, straight out of the bag.  But, in general, that’s not the problem being addressed by use of “pet-safe” de-icers.  A mouthful of de-icer is going to be bad for your pet, no matter what.

Instead, people who buy pet-safe ice melt are worried about dogs walking on areas treated with (e.g.) rock salt as an ice-melter.  First, salt irritates dogs’ paws.  And second, dogs ingest salt from licking off salt crystals stuck on or in their paws,

The upshot of all that is that rock salt (NaCl) is something you don’t want to see in a “pet-safe” ice melt.

So what do I find, off the crack of the bat, on the Home Depot website?

And that’s not a one-off accident.  Here’s the same nonsense from Uline, a supplier of industrial products of all types:

So …

Once you move beyond colored rock salt — clearly not pet-safe — there’s some real ambiguity as to what’s safe or not.

Urea is typically considered fully safe for dogs and cats (but is not safe for ruminants).  But urea is basically high-potency nitrogen fertilizer.

I can’t see myself dumping a 50-pound bag of 43-0-0 fertilizer on the driveway in winter.  Or in any season, really.

Plus, it’s a poor ice melter, and you’d be hard-pressed to find it bagged in bulk for consumer ice-melt use.  Apparently, it is only commonly used in specialty situations such as elevated metal walkways, where lack of metal corrosion is the key concern for the ice-melt.

Acetate ice melters (calcium magnesium acetate (CMA) and potassium acetate (KAC)) are considered pet-safe by some.  But these, too, perform relatively poorly as ice-melters, and are expensive per effective melting dose, as well.  They have the additional advantage of not being chloride salts, and so being less toxic to the aquatic environment than (say) rock salt.

Beware “with CMA”, just as you should beware pet friendlier.  A lot of ice-melt blends want to bask in the glow of CMA without the bother and expense of actually including much of it in their blend.   (Plus, the ice melter probably works better as an ice melter if you go light on the CMA, because CMA apparently is not a very good ice melter.  It just has the big advantage of killing less stuff than chloride salts do.)

Magnesium chloride is considered safer for pets than other chloride salts.  It is sold, for example, by both PetSmart and PetCo as a pet-safer de-icer.  It also performs quite well as a de-icer.  From a pet-safety standpoint, the only drawback appears to be price.  In retail packaging, MgCl2 appears to cost anywhere from five to ten times as much as rock salt.  But, as a chloride salt, this is not materially better than rock salt, from the standpoint of toxicity to the aquatic environment.  And some references suggest that it causes more damage to concrete than rock salt does, particular to newer (under-one-year-old) concrete.

Conclusion

I have no dog in this fight, if you will excuse the phrase.  I don’t own a pet, so this isn’t my problem.  I only stumbled across it in looking for ice melts that aren’t chloride salts, hoping for lower environmental impact.  And was vaguely outraged once I figured the whole pet-friendlier thing as discussed above.

But I note that it is a common and accepted practice in the ice-melt market to take a bag of common rock salt, color it (green or blue, inevitably), sprinkle in some actually pet-safe materials, slap “pet-safer” on the bag, and then double the amount charged for it. 

Unlike pet food, nobody appears to regulate anything about “pet-safer” de-icers.  Even though the danger arises from pets eating the stuff.  Contrast that the the multi-agency Federal regulation of pet food.  (Not that the Feds need to regulate de-icers per se, but the use of “pet-safer” and similar legal-but-misleading claims.)

Unsurprisingly, then, a lot of stuff offered in the big-box hardware stores as “pet-safer” ice melt is just rock salt (plus a tiny amount of additives) sold at a steep markup.

Caveat emptor.

Post #2084: Homeopathic pavement treatment.

 

I’m no longer going to use pavement de-icer (rock salt, road salt, ice melt).

For now, at least.

That’s because, upon inspection, much about the modern road salt/pavement de-icer market confuses me.

But in my defense, I had a lot of help, getting confused.  The whole retail “de-icer” market pings my bullshit detector in some strong and unpleasant ways.  Not just the simple stuff (“melts as low as … ).  More importantly, “pet-safe” and “eco-friendly” have quietly morphed into their mealy-mouthed “safer” and “friendlier” versions.  And not in a good way.

Road salt is a deep topic, but I have to start somewhere.

As described in Section 1 below, I did not intend to fuse the principles of homeopathy with those of winter pavement maintenance.  That happened entirely as a result of my own stupidity.

But, per Section 2 (next post), I had a lot of help being stupid about it.  Pavement de-icers are arguably the worst consumer product I’ve ever seen, in terms of manufacturers’ claims and deliberately misleading marketing.

Plus, Section 3, the practical use of chemical pavement de-icer is complicated. Even absent all the baloney presented by sellers of de-icers, there’s a lot to unpack.  I’m not sure I understand the chemistry part of it, yet, let alone the weather’s contribution.

And, Section 4, most (perhaps all) commonly-used de-icers are crap for the environment, especially the aquatic environment.  I can’t complain about the taste of road salt in the drinking water if I’m spreading this stuff on my own driveway.

This is just the first of several posts on pavement de-icer.

Part 1:  Driveway homeopathy

1A:  The hasty but satisfying post-hoc conclusion

Source:  Good ol’ clipart-library.com, which has upped its game with an on-the-fly AI picture generator.

A few days ago, I salted my driveway, using calcium chloride pellets.  The idea was that the (calcium chloride) salt would melt a coming light snow, causing it to run off my driveway as (slightly salty) water, and, ideally, leaving me with bare pavement. Instead of a driveway with an inch of snow on it.  This, as being preferable to re-shoveling my driveway to remove a light coating of snow.  And this to be achieved despite temperatures consistently (but not hugely) below 32F.

By the end of the next day, my driveway was dry and snow/ice free.

So the salt obviously worked, right?  End-of-story.

Part 2:  But … science

As I was patting myself on the back, I could not help but notice that all my neighbors’ driveways were also dry and snow-free.

Which, after a moment’s solemn reflection, pretty strongly suggested that my salting my driveway was a complete waste of time.

I’m pretty sure none of my neighbors salted theirs.

Part 3:  thus was born the short-lived science of driveway homeopathy.

First, I found a pretty chart.  (This is, in fact, an excellent chart from an excellent practical reference.)

Source:  National Tank Outlet.  These folks sell the tanks you need to store this stuff at industrial scale.

Those substances are all salts, chemically speaking:

  • CaCl2 — calcium chloride
  • NaCl — salt– rock salt — halite — sodium chloride
  • MgCL2 — magnesium chloride
  • CMA — calcium magnesium acetate ( calcium acetate and magnesium acetate).
  • KAC — potassium acetate.

Then doing this crude calculation:

And then, only as a last resort, actually reading the directions on the bag.  Which, they just flat out say, per for 1000 square feet, for some “typical” conditions (I guess), I should use just touch more than what I calculated above.

The upshot is that I should use at least an entire 50-pound bag of calcium chloride.  On a 1000-square-foot section of driveway.  That, to get rid of an (one) inch of typical snowfall.  That should make a brine strong enough to have all that snow turn to water and run off, even though the weather is (maybe) 10 degrees below freezing.  This, instead of shoveling the driveway, again, for the new inch of snow that fell.

I’ve never used it at anything close to that rate.  I use it a few pounds at a time.  (And, correspondingly, my first (and current) bag of calcium chloride is at least a decade old.)  Nor will I ever.

Ergo, I have been engaging in homeopathic ice melting.  Sure, I start off with strong brine, when those first few snowflakes hit those salt (calcium chloride) crystals (pellets).  Implicitly, I must have believed that after adding a whole lot more water (in the form of an inch of snow), the resulting very dilute brine would somehow recall the strength it once had, and so continue to melt the snow.

Contrary to the laws of physics and chemistry.  Or common sense.

Or the directions on the bag.

Or all of the above.

Conclusion

For now, the simple message is that homeopathic pavement de-icer helps no-one.  Avoid it.

It achieves nothing while causing slight environmental harm. It’s a net negative, except perhaps in (easily deceived) the mind of the user.

So, with regard to salting the pavement:  Do.  Or do not.

Crazily enough, I have a lot more to say about ice melters.  That’ll come out in the next posts.