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Geophysical Research Abstracts, Vol. 9, 04712, 2007SRef-ID: 1607-7962/gra/EGU2007-A-04712 European Geosciences Union 2007 Characterization of mortars used since baroque period
on altar of St. Jacob Church (Ljubljana, Slovenia)
S. Kramar (1), B. Mirtiˇc (2), M. Gregerová (3)
(1) Institute for the Protection of Cultural Heritage of Slovenia, Restoration Center, Slovenia.
(2) University of Ljubljana, Faculty of Natural Sciences and Engineering, Department ofGeology, Slovenia, (3) Masaryk University, Faculty of Science, Institute of GeologicalSciences, Czech Republic ([email protected]) Determination of the type of mortars has an important meaning for monuments preser-vation. Such identification enables reconstruction of original mortar composition,helps to identify provenience of the applied raw material and can prove the technol-ogy of mortar manufacturing. Restoration intervention demands use of material whichresembles the original material or producing appropriate material which is compat-ible with the properties of original material. Thus, first step for production of newrepair mortar that can be used is in determining the composition of original mortar,the technology of its manufacturing and its deterioration phenomena.
Present study deals with characterization of some mortar samples taken from altar inSt. Jacob Church in Ljubljana, which have been applied since baroque period, in senseto determine original historical mortars and those which represent the repair mortars,applied during later restoration intervention. Special attempt was put on presence ofsoluble salt crystallization as one of the significant reason for mortar deterioration.
Within the framework of research optical microscopy, scanning electron microscopy(SEM), coupled to energy dispersive x-ray spectrometer (EDX), X-ray diffractiontechniques were used to determine mineralogical composition of mortar samples andto determine present soluble salts. Characterization of these mortars based on petro-logical and mineralogical composition of used aggregates and binder in particularmortar sample, grain size, shape and particle size distribution of aggregate. In sam-ples of mortars considered as original mortars aggregate/binder ratio was determinedas well.
Results show that during this period a different types of mortars were used, differin place and time of their application. It is obvious that mortars of original applica-tion are all lime mortars. We could distinguish two types of lime mortars, one withcrushed limestone and wood particles and the second with river sand as aggregate.
Original lime mortars differ in type of aggregate dependent on place of mortar appli-cation. Aggregate/binder ratio in these mortars varies between 1/1, 5 and 1/3. Latestrepair mortars were mainly cement - lime mortars with aggregates of different petro-logical composition. As a result of degradation processes some soluble salt presenton and within mortars were determined (gypsum and magnesium sulphate hydrate indifferent hydrated states). In determining different type of mortars, we tried to give areliable instruction for place of application of different type of mortars for the needsof restoration intervention.

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