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KEY WORDS : Experimental Method, Evaluation of Restoration Materials, Lime Mortars, Lime Plasters, Experimental
Techniques of Materials, Reproduction of Mortars, Design of Repair Mortars
ABSTRACT:
Our country is quite rich with historical buildings. Depending on various factors like time, increasing air pollution due to
technological improvements of present era together with insufficiency of inspection lead to the formation of damages on these
buildings which are part of our historical heritage. Conservation of such buildings which are as important as historical documents
should be the first and foremost target of any project. Where maintenance is insufficient, conservation and restoration attempts
should replace it. What is necessary in restoration is the use of material which resembles the original material to the closest degree or,
producing appropriate material which is compatible with the properties of the original material. The first dimension of the current
problem is the insufficiency of resources while the second dimension stems from the lack of proper evaluation of the material to be
used in conservation and restoration. This study defines the importance of mortars and plasters along with their history and the
reasons of deterioration. In addition, it sets up the information flow of mortar and plaster within a systematic decision making
process. The necessary experimental methods for the production of new repair mortar or plaster that can be used in determining the
character analysis of original mortar and deterioration morphology are also analyzed. Thus, a method that can be used in the
conservation and restoration studies is determined with this paper.
1. INTRODUCTION
The number of different materials used in the historical
buildings is limited. Generally, available regional materials had
to be used due to necessity during the construction. What we
name as traditional materials are consisted of stone, brick,
wood, mortar and plaster. Among these, plasters and mortars are
greatly affected by environmental factors and hence they are the
ones that necessitate conservation and repair the most.
Besides their functional necessity during the construction of the
building, mortars and plasters carry an aesthetic value
depending on their architectural form and construction
techniques. Even though mortars and plasters serve different
purposes within a building, their deterioration morphology and
conservation attempts should be analyzed together since they
are basically made out of similar materials. Mortar is a
structural material that brings stone or brick together, which
provide the stability of the wall. On the other hand plaster
covers the façade of the building and preserves the material that
constitute the structure of the wall from external weather
conditions. Thus, plaster is not a structural material, it only
serves to protect the building’s facade. While investigating the
deterioration of mortar and plaster, which serve different
functions, it is necessary to investigate if there is a decrease in
their common and functional features, (if there is any). For
example, as different from plasters, compression resistance and
elasticity modulus of mortar, which bind the stone or brick
together, is quite important. On the other hand, optimum water
vapour permeability values, durability against acids or gas in the
air, thermal dilatation and swelling by water are common
S. Acun , ITU, Architecture Faculty, 80191 Istanbul -Turkey.
important factors for both mortar and plaster. Among the
historical mortars that have come to survive up until today,
gypsum, lime and lime pozzolana have been used as
binding materials. As aggregate material, river sand, pebbles,
brick pieces and powder have been used together with hay,'
horse hair, goat hair which have served as fibers. In our country
we encounter Horasan mortar with varying mixture ratios in
buildings from Byzantion, Seldjuki and Ottoman periods. This
type of mortar is as strong as concrete and is made by binding
lime together with varying proportions of river sand and brick
pieces/powder that are used as aggregates. Horasan mortar has
been widely used in Ottoman buildings especially in those that
belong to the 15 th century and in the period that follows. In 18 th
and 19 th centuries, lime mortar, named as “royal mortar” which
was made of Italian pozzolana “poqdana”, has been used. Lime
mortar is actually composed of non-hydraulic lime, which is
irresistant to water, combined with pozzolana. In this way
hydraulic lime is formed which is hard and resistant to water at
the same time. Hence, it is also known as Horasan concrete in
history. Lime mortar made out of pozzolana and brick pieces
have been named by the Romans as “opus cementicium” and
they have continued to survive until today. In addition these
mortars have served to improve the cement technology of today.
Towards the 20 th century, the hydraulic quality of cement and
its feasible use has been combined with positive features like
low stress, high deformation capacity and porosity of lime
mortar and as a consequence, lime-cement mortar production
has begun.The first step in the evaluation of mortar and plaster
used in historical buildings is the accurate determination of the
original material used and the reasons that have led to
deterioration. The table in the following briefly summarizes the
deterioration causes of mortar and plaster.
