There are various reasons for having mortar analyzed. Strength,  contamination /
deterioration, hazardous materials, mortar matching and who knows what else. I
find it is rare that mortar is analyzed for anything other than for matching
existing materials. This may be due to the line of work I am in.

For matching of mortar since the 1940's, it is generally made up of portland
cements and standardized sands and aggregates. The more current the completion
date of the building project, the use of various additives gets more controlled.
With standardized mortars, matching is not too difficult.

For lime based mortars without portland added, the materials were most likely
locally available to the building project. The limestone was local, the burning
of the stone to quicklime was done local or on site, the slacking might have been
done on site, the sand came from the local stream or river. I have not seen a
mortar analysis for a historic lime mortar that was useful for matching the
existing historic mortar. There are too many local variations for the "lab" to
put into useful information. The tiny bits and pieces of unburned limestone are
digested and figured into the fines, sands and aggregates. The lime is calculated
as modern high temperature gas fired bag lime and not as lower temperature wood
fired local stone. Bagged sands are generally too uniform to provide the texture
and color needed to match the historic mortars. The mason is not given the
flexibility in his pricing to take the time to play with the materials to get the
right combination. As a result, masonry colorants are added to obtain the color
and matching the texture is generally not even attempted.

For the mortars from the in-between time period, there are mixtures with all
sorts of lime to portland ratios plus pounds and pounds of various additives.
Sometimes bagged standardized sands and aggregates were used. Sometimes local
materials were used. Some mixes were placed with way too much water causing less
homogeneous mixes cause irregular results . Masons, plasterers, renderers,
engineers, architects playing with portland using lime experience. That is a
one-way ticket to disaster just as today, people with only portland experience
trying to use lime based mortars. Two different beasts, two different methods od
taming the beast.

This probable does not answer your question. What was the question again?

Bryan
==========


Met History wrote:

> [log in to unmask] writes:
>
> <<  At Dell Corporation, we find that mortar analyses reports for mortars
> that are 50 to 60 years old or less can be useful to the guy in the field. >>
>
> Bryan, what are they useful for?  Solely for matching the existing mortar?
> Or is there some larger diagnostic function?  And does your post indicate
> that analysis of mortars older than half a century is not useful?
>
> Christopher Gray (formerly known as Struck Joint)