Spanish fort made of cut coral blocks

Anna Shepherd <a_k_shepherd [at] hotmail__com> writes

>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.
>...
>... 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.

Chris Cleere (Conservation DistList Instance: 21:18 Wednesday,
August 1, 2007) has given an excellent summary of mortar composition
and its method of application. I agree in totality that it is quite
locality specific when it comes to mortar mix recipes considering
different contextual circumstances.

I would recommend you to get in contact with the National Historical
Institute (NHI) <nhi [at] i-next__net> located in Ermita, Manila. Over the
years, they have extensive knowledge in the conservation of masonry
structures that comprise of corals in Philippines. The NHI
recommends the following mortar mix proportion in their 2005
publication "A technical note on the restoration of stone and
masonry in historic buildings", which they have stated that it is
not absolute and must be tested as to their applicability and
appropriateness.

    1.  For very low strength

        1 part cement (Portland type I, white Portland or Pozzolan)
        binder

        3 parts lime (hydraulic) binder

        12 parts sieved sand filler

    2.  For moderate strength

        1 part cement (Portland type I, white Portland or Pozzolan)
        binder

        2 parts lime (hydraulic) binder

        9 parts sieved sand filler

    3.  For good strength

        1 part cement (Portland type I, white Portland or Pozzolan)
        binder

        1 parts lime (hydraulic) binder

        6 parts sieved sand filler

    4.  For ideal strength for bricks

        1 part cement (Portland type I, white Portland or Pozzolan)
        binder

        1 parts lime (hydraulic) binder

        4 parts sieved sand filler

    5.  For special applications

        1 part cement (Portland type I, white Portland or Pozzolan)
        binder

        1 parts lime (hydraulic) binder

        1/2 part brick or adobe powder

        4 parts sieved sand filler

I am not too sure what "special applications" meant, but I reckoned
that it is used as a shrinkage reducer as well as the colour of the
brick or adobe powder to match the existing masonry structure.

Yeo Kang Shua, PhD
Architectural Consultant
Preservation of Monuments Board
Singapore


                                  ***
                  Conservation DistList Instance 21:19
                 Distributed: Wednesday, August 8, 2007
                       Message Id: cdl-21-19-004
                                  ***