Return to index: [Subject] [Thread] [Date] [Author]

RE: Masonry Cement

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Mortar cement has a minimum bond strength specified by ASTM C 1329, masonry
cement does not have any specified requirement for bond strength specified
by ASTM C 91.  ACI 530 allows you to use the same flexural tension values
for mortar cement as for Portland cement/lime mortar.  The values it allows
for masonry cement are much less.  That is the primary reason that I allow
the use of mortar cement.  I also think that if the masons find it easier to
work with than Portland cement/lime mortar they will do a better job.
What is the reason that you object to mortar cement other than being
uncomfortable with not knowing the composition of the blended cement?  The
reason I mentioned concrete additives was to point out that they form a
product other than the historically pure "concrete".  They consist of
concoctions that we really don't know much about but we either accept or
reject based on what others tell us about them.

Roger C. Davis
SDS Architects, Inc.

-----Original Message-----
From:	Roger Turk [mailto:73527.1356(--nospam--at)]
Sent:	Monday, July 02, 2001 11:25 AM
To:	seaint(--nospam--at)
Subject:	RE: Masonry Cement

Yes, I meant Mortar Cement (ASTM C 1329/UBC Standard 21-14).  Masonry Cement
(ASTM C 91) is the other proprietary product that I prohibit.

The "Physical Requirements" for Mortar Cement  (UBC Std. Table 21-14-A)

Fineness residue on a No. 325 sieve, max. percent
Autoclave Expansion, max. percent
Time of setting, Gilmore method, initial & final (min/max hours)
Compressive strengh, 7 and 28 day, min. psi
Flexural Bond strength, 28 day min. psi
Air content of mortar, max. & min. percent by volume
Water retention, min. percent

Table 21-14-B lists "Restricted Materials" and Table 21-14-C lists
"Deleterious Materials Not Permitted in Mortar Cement."  At no place in the
standard is there any requirement for portland cement to be one of the

Thanks for bringing this misstatement to my attention.

In this climate of high temperatures and low humidities, admixtures in
concrete are almost required.  When ambient temperatures are above 90 deg F,
which is generally all the time between May and October, I specify water
reducing or retarding admixtures, or a water reducing-retarding combination

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

Roger Davis wrote:

By "masonry mortar" do you mean "Mortar cement" or is this another variant?
The information I have is that "Mortar cement" does meet the strength and
the proportion requirements of ASTM C-270.  That may mean that a blended
cement is used instead of an entirely Portland cement but it will still
contain Portland cement.  The reason I allow it is because you can use the
same tensile stresses permitted for lime-cement mortars.  It may not be as
"pure" as lime-cement mortar but I don't know of a problem with it.

I am reluctant to allow additives to concrete mixes also - even though I
believe potable water probably does more damage to concrete that most

Roger C. Davis
SDS Architects, Inc.

-----Original Message-----
From:   Roger Turk [mailto:73527.1356(--nospam--at)]
Sent:   Friday, June 29, 2001 3:55 PM
To:     seaint(--nospam--at)
Subject:        RE: Masonry Cement

I prohibit the use of both masonry cement and masonry mortar.  If you check
out the specs for both of these, in either ASTM or UBC Standards, you will
see that the specs are mechanical and strength requirements and neither spec
requires *any* portland cement to be included.  Both products are
and the actual constituents are secrets of the producer.

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

Roger Davis wrote:

. > Don't allow it.  The bond strength is not as good and it is not as water
. > tight as lime/cement mortar.  There is much more entrained air in
. > cement which decreases the bond strength.  The strongest argument I have
. > heard for the use of masonry cement is that the masons find it easier to
. > work with and they will do a better job than if they are forced to work
. > with lime/cement mortar. La Farge and at least one other company in the
. > mid-west have a product that is called "mortar cement". I think it has
. > the good properties of lime/cement mortar and it is easier to work with
. > for the masons. Some people think that masonry cement and mortar cement
. > are the same thing. We specify that is it is equally acceptable to
. > lime/cement mortar but make clear that masonry cement is unacceptable.

. > Roger C. Davis
. > Architect
. > SDS Architects, Inc.

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at:
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*   Questions to seaint-ad(--nospam--at) Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: 
******* ****** ****** ****** ******* ****** ****** ********