[Greenbuilding] concrete & frost

[Norbert Senf]

At 12:56 PM 11/5/2007 -0500, LarenCorie wrote:
>From: "Robert Tom" <ArchiLogic at yahoo.ca>
>
> > The admixture that is typically used to make concrete
> > workable at  below-freezing temperatures is calcium chloride
> > -- a salt.

Actually, calcium chloride is an accelerator. It makes the concrete set
faster, so that the hydraulic set happens before the frost gets a chance
to damage the concrete. The accelerated setting would also be exothermic.

Calcium aluminate cement is similar to portland, except that it is refractory.
It also has a very high exotherm, so is used in low temperature work. It is
super high early, and gets about 90% of its full strength after 24 hrs. It
also gives the best impression from a mold, and 
is used by artists for castings.

Norbert

-------------------------------------------
Norbert Senf---------- mheat(at)heatkit.com
Masonry Stove Builders
25 Brouse Rd.
RR 5, Shawville------- www.heatkit.com
Québec J0X 2Y0-------- fax:-----819.647.6082
---------------------- voice:---819.647.5092