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RE: Portlands vs. Blended Hydraulics

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Robert,

If you read the specs on masonry cements, masonry mortar, etc., you will 
probably be surprised, as I was, to learn that portland cement is **NOT** a 
required ingredient!  Masonry cement and masonry mortar are proprietary with 
the manufacturer and as long as they meet the mechanical requirements of the 
specs and the strength requirement, they can contain anything.  Table 21-11-A 
of UBC Standard 21-11 for Cement, Masonry in the 1997 UBC (Volume 3) lists 
only requirements for:

   Fineness
   Soundness
   Time of Setting
   Compressive Strength
   Air Content of Mortar
   Water retention, Flow after suction

My specs will not allow use of these, nor will it permit use of lime 
substitutes.

Hope this helps.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Robert Rollo wrote:

>>is there chemical difference between portland plus lime and masonry cements?

or are masonry cements simply premixed with the lime?

seems like i had heard once (with no confirmation) that portland plus lime is
better than allowing masonry cements, primarily due to the leaching of salts
responsible for efflorescence.

we typically spec ASTM C270 proportion spec for S with portland and lime for
this reason.

have i lost my mind on the efflorescence and should i be performance
spec'ing and forget the efflorescence issue ?

thanks in advance.<<