Spanish fort made of cut coral blocks

I am currently assisting a local heritage team on a small island in
the Philippines with the conservation of their fort. It was built by
the Spanish in the mid 1600's, and is made of cut coral with lime
mortar. At the moment the fort has extensive structural damage due
to weathering and vegetation growth on and around the fort. Many of
the blocks are falling away due to mortar loss, the stresses have
caused turrets to break off from the fort walls, and one wall is
completely bowed from modern infilling material placed behind the
wall.

Having not had much experience in architectural conservation, I am
wondering if anyone has any information on how best to repair such a
site, in particular the leaning towers and major structural cracks
which are threatening to collapse. Also, I am wondering if anyone
has any information on an appropriate mortar that can be used in
conjunction with cut coral bricks. Being a small provincial island,
with most of the work being volunteer, it is extremely difficult and
exorbitantly expensive to obtain chemicals here, therefore any
information on easily obtainable 'recipes' that would not be
confused with the original mortar would be greatly appreciated.


                                  ***
                  Conservation DistList Instance 21:17
                  Distributed: Saturday, July 21, 2007
                       Message Id: cdl-21-17-019
                                  ***