[Greenbuilding] Calcium chloride admixutres (was re: concrete &frost)

[Alan Abrams]

<Calcium chloride should not be used where reinforcing steel is present.>
So says the (US) Federal Highway Administration:
http://www.fhwa.dot.gov/infrastructure/materialsgrp/acclerat.htm


Back in the 80's, the popular "calc" admixture was banned in at least one
local jurisdiction 'cause it attacks metal reinforcement.  

I therefore forbade it on a project in another location where it was still
legal.  This was something like Dec 10.  Our early Decs are usually mild,
but a sudden windy cold snap was predicted -- so 9:00 pm found me
numbfingered, wrestling frost blankets across wall ties and anchor straps,
trying not to shake the marginally braced wall forms (and cracking them all
to hell), cursing the moon like a drunken stevedore.  Might as well have
stayed home.  

The low that night was 17d Fht.  Stayed way below freezing for several days.


My normal method for testing concrete strength of a foundation wall is to
tap it with a 22 oz Estwing (smooth face!!).  If the claws ring, you've got
a good tight batch.  When I performed the test after the forms were
stripped, all I got was a dull thud.  I kept checking through the winter;
finally in spring I got that nice teeeeng sound.  That was getting on 20 yrs
ago, and the house is doing fine...

AA



Alan Abrams, AIBD
Abrams Design Build
a sustainable approach to beautiful space
alan at abramsdesignbuild.com
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