FreeLists / homeclinic / [homeclinic] Re: quiz homeclinic salting sidewalks

["Kenneth J. Kovler" <kkovler@xxxxxxxx>]

Once upon a time on Wed, 7 Mar 2001,at 10:57pm Cary W Mcconlogue wrote...

>
> Ok, I'll try....

> >
> False.  De-icing chemicals lower the freezing point of water only when
> they are dissolved.  There is typically enough localized melting in
> snow and ice to dissolve a bit of chemical - that bit helps to melt
> more snow or ice which dissolves more chemical, etc.  Eventually, you
> have a salty solution that freezes at a much lower temperature
> (depending on how much salt you throw down.)
>
> Extension of the theory:  If it's cold enough, forget about the salt.
> It will just sit on the ice and do nothing.
>
> > > >
> > > > 2)True or false:  chemicals used  for De-icing sidewalks do
> > not attack
> > > > concrete.
> > > >
>
> True.
>

Hooray! We have a winner.


Again, let me say that this list is open to anyone who has a question or a
comment or even would like to post an interesting url to a web page. Just
make sure it deals with things in and around the house or home.

Until next month, (hopefully we will have something to talk about before
then) repair something or if you must, replace it!

 ken (list owner)
====================================================================
Here is some of the reasoning I have sorted out on the above questions.

1.false; None of the common De-icing chemicals are incapable of melting
snow and ice in their dry (solid) state. They first must attract or come
into contact with moisture to form a brine (a chemical/water solution).
The brine then penetrates down through the ice and snow until it reaches
the pavement. Once on the pavement surface, it spreads outwards melting
and under cutting the ice and snow for mechanical removal, which means
plowing or shoveling. Even though the same chemical behavior is involved,
there are remarkable differences in how deicers work. When researchers
compared the De-icing effectiveness of various deicers at 15oF, calcium
chloride pellets melted more ice than any of the other deicers. At 5oF,
the difference was even more dramatic. One reason for these big
differences in De-icing is that some chemicals take longer to go into
solution before they can begin penetrating ice and snow. Even though snow
and ice are merely frozen water, moisture is not readily available at
freezing temperatures, so liquefication is slowed. Of all the chemicals,
calcium chloride and magnesium chloride have the greatest ability to
attract and retain moisture from its surrounds. Of these two deicers,
calcium chloride is superior.

2.true, None of the common deicers chemically attack concrete. But, by
depressing the freezing point of water, all deicers can affect the number
of freeze/thaw cycles concrete goes through. The expansion pressure from
water causes concrete to spall.

research conducted by the Portland Cement Association indicate that
quality air entrained concrete, properly cured is much more resistant to
freeze/thaw scaling than improperly cured or non-air-entrained concrete.

 Learn more
http://members.tm.net/henryk/deicers.htm non-air-entrained concrete.

Manufacturer's usage recommendations should always be followed to prevent
over applying deicer. Once the bond between ice and pavement is broken,
the slush and residual deicer should be
removed to prevent re-freezing. Following this procedure, concrete scaling
will be minimized.


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