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Re: Masonry mortar

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Harold,

As much as I would love to take full credit for what I posted, I should
make sure it is clear that I typed verbatim what was in the textbook that
I mentioned.  Thus, it is not really my "assessment" but rather a quote
from a book.

Regards,

Scott
Adrian, MI


On Tue, 12 Oct 2004, Harold Sprague wrote:

> I will expand a bit on Scott's reply.  Scott is correct in his assessments
> of mortars.  My response is from the experience one gains within spittin'
> range of the masons.
>
> The N mortars have a higher lime content and have better self crack healing
> characteristics.  The S and M mortars, while stronger, have a shorter board
> life.  As such they will generally deveolp more plastic shrinkage cracks,
> and can have a bond problem if the masonry contractor is running behind.  M
> mortars are best used when back parging cavities below grade.
>
> When considering tuck pointing, match the mortar that is in place.  When in
> doubt go to an N mortar for tuck pointing.  S mortars in tuck pointing can
> cause problems.  It is best to take a sample, send it in for petrographics
> and develop a match mortar.  S is still your exposed normal mortar, and most
> used for exterior applications.
>
> Regards,
> Harold Sprague
>
>
>
>
> >From: Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu>
> >Reply-To: <seaint(--nospam--at)seaint.org>
> >To: seaint(--nospam--at)seaint.org
> >Subject: Re: Masonry mortar
> >Date: Mon, 11 Oct 2004 17:36:59 -0400 (EDT)
> >
> >Michael:
> >
> >From "Masonry Design and Detailing for Architects, Engineers and
> >Contractors" by Christine Beall (third edition):
> >
> >"Type M is a high-strength mix recommedned for both reinforced and
> >unreinforced masorny with may be subject to high compressive loads.
> >
> >Type S mortar produces tensile bond strengths which approach the maximum
> >obtainable with cement-lime mortar.  It is recommended for structures
> >subject to normal compressive loads but which require flecural bond
> >strength for high lateral loads from soil pressures, high winds, or
> >earthquakes.  Type S should also be used where mortar adhesion is the sole
> >bonding agent between facing and backing, such as application of
> >adhesion-type terra cotta veneer.  Because of its excellent durability,
> >Type S mortar is also recommended for structures at or below grade and in
> >contact with the soil, such as foundations, retaining walls, pavements,
> >sewers, and manholes.
> >
> >Type N is a good general-purpose mortar for use in above-grade masonry.
> >It is recommeded for exterior masonry veneers and for interior and
> >exterior loadbearing walls.  This "medimum-strength" mortar represents the
> >best compromise among compressive strength and flexural strength,
> >workability, and economy and is, in fact, recommended for most masonry
> >applications.
> >
> >Type O is a "high-lime," low-strength mortar.  It is recommended for
> >interior and exterior non-loading bearing walls and veneers which will not
> >be subject to freezing in the presence of moisture.  Type O mortar is
> >often used in one- and two-story residential work and is a favorite of
> >masons because of its excellent workability and economical cost.
> >
> >Type K mortar has a very low compressive strength and a correspondingly
> >low tensile bond strength.  It is seldom used in new construction, and is
> >recommeded in ASTM C270 only for tuckpointing historic buildings
> >constructed orginally with lime-sand mortar."
> >
> >HTH,
> >
> >Scott
> >Adrian, MI
> >
> >On Mon, 11 Oct 2004, Michael L. Hemstad wrote:
> >
> > > All,
> > > I've decided to fill yet another annoying gap in my knowledge base.
> > > What is general practice for specifying different types of mortar (M, S,
> > > or N)?  Typically, I have specified these based on where they are
> > > located (exterior, below or above ground; or interior, respectively).
> > > Does the specified masonry strength play into the choice of mortar, or
> > > only the end use?  Amrhein's book has some information, but not much
> > > explanation.
> > >
> > > Thanks for any help.
> > >
> > > Mike Hemstad
> > >
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