John Melander wrote:
>The use of ground
limestone as opposed to hydrated lime affords a significant energy
savings in producing a masonry cement.<

I hate to say "I told you so" (but the archive would probably support that
statement).

I agree with Mr. Melander that the required workability and performance are
readily achieved with masonry cement based on crushed limestone, but there
are other differences which may be of significance in repointing of softer
masonry. In particular, our observations seem to indicate that hydrated
lime/cement based masonry mortars become softer and more plastic when wet
than limestone/cement based mortars. 

Considering the relatively small material cost for repointing (as opposed
to labor) we're inclined to keep using the more expensive hydrated lime.

Mike E.