According to the results of the archaeometry analyzes performed on 3 mortars, 3 plaster and 2 stone samples taken from the Mor Yakup Church, the binder, filler and additive types and proportions (by weight) of the mortar and plaster samples and the physical and petrographic qualities of the stone samples were obtained.
In the spot anion tests (Cl−, SO4 2−, CO3 2−, NO3 −) applied on mortar, plaster and stone samples, sulphate (SO4 2− ) salinization was detected in low amounts in mortars and plasters, but not in stones (Table 1). There is a very high rate of chloride (Cl−) type salinization in all of the samples. The most basic situation reflecting this situation should be the cement-containing mortars used in the repair. A very high amount of nitrate (NO3−) type salinization was determined in all of the samples. The source of this type of salinization is environmental effects (especially from the exhaust gas effect). Nitrate has a role in intense black layering, which can be observed visually, especially on stone surfaces. It is interesting that the samples did not contain dissolved carbonate (except for Example 4). This indicates that the structural segregation is low in these samples. Organic additives (plant, straw, tow, etc.) were not determined in the aggregate structure of the mortar samples. In plaster samples, on the other hand, it was determined at a very low rate in Sample 4 and Sample 5. While protein and oil content were not found in the mortar samples, the oil amount was determined in Example 4 of the plaster samples. The oil content determined in this example is due to the effect of the black layer. The black layer has also caused carbonation towards deterioration and decomposition in the same sample (Table 1,2). In support of this situation, when the black layer samples on the plaster were analyzed separately in terms of protein and oil contents, protein was determined in the samples (Table 2).
The total water-soluble salt content of the mortar and plaster samples is quite high as expected since they have lime-type binders. The total salt content in mortars varies between 6.5–18.8% (average 12.07%) and in plasters between 11.1–14.8% (average 12.93%) (Table 1). The total salt contents of the limestone (Sample 7) and travertine (Sample 8) stone samples were 3.1% and 3.5%, respectively. The rates determined by considering the porous structure of the stones are quite high and at a level that will create a destructive effect (Table 1,3,5c). The source of the determined salinization is the decomposed joint and rubble filling mortars and plasters.
The physical properties of the structural samples were determined by the basic physical tests (BHA: unit volume weight, SEK: water absorption capacity, P: porosity, SH: Schmidt Hammer hardness and SV: ultrasonic velocity measurement) (Table 3). The saturated/dry unit weights of the mortars (Examples 1–3) are respectively 1.92–2.15 g/cm3 (average 2.05 g/cm3) / 1.54–2.05 g/cm3 (average 1.79 g) /cm3), the saturated/dry unit volume weights of the plasters (Examples 4–6) are respectively 1.80–1.99 g/cm3 (average 1.90 g/cm3) / 1.58–1.94 g/cm3 (average 1.76 g/cm3). The unit volume weights of the mortar samples are higher than the plasters. The water absorption capacity and porosity of the mortar samples are between 2.19–16.62% (average 7.52%) / 4.50-25.67% (average 12.30%) respectively, and the water absorption capacity and porosity of the plaster samples are also they vary between 1.17–10.90% (mean 4.54%) / 2.28%-17.17% (mean 7.39%), respectively (Table 3). Samples with high unit weight and low porosity are expected to be more durable. Mortar samples have a higher unit volume weight than plasters on average values. Sample 1 from the mortar samples and Sample 4 from the plaster samples are similarly the samples with the lowest strength. When the physical properties of the stone samples are evaluated, the limestone (Sample 7) and travertine (Sample 8) samples have similar physical properties (Table 3). However, although the limestone sample seems to be slightly more durable than the travertine sample in terms of its basic physical properties, it has been determined that the travertine sample exhibits a more homogeneous rock structure than the limestone sample with the ultrasonic velocity measurement value (Table 3).
Mortar samples contain moisture content varying between 18.38–18.94%. Plaster samples (Samples 4–6; average 11.10%) are in a more humid environment than mortar samples (Samples 1–3; average 4.47%). Organic carbon content was determined between 4.44–5.52% (on average 5.51%) in the structure of the mortar samples, and between 9.29–16.67% (on average 11.99%) in the structure of the plaster samples. Organic tow (plant, straw, etc.) added to the structure of the plaster samples in order to increase the adhesion to the surface can be observed in the plasters in a way that differs from the mortars (Table 4).
The total carbonate content of the acidic treated mortar samples varies between 96.67–97.40% (average 97.12%), and in plasters between 93.01–99.51% (average 97.13%). Both the loss of ignition and the carbonate content determined in mortars and plasters by acidic treatment are quite high (Table 4). The total carbonate content of the samples is directly related to the lime content. The lime/carbonate dense binder content of the joint mortar and plaster samples of the building does not show compatibility with the binder aggregate (1:2 and 1:3) content seen in traditional applications.
The size of the aggregates obtained after the acidic treatment applied to the mortar and plaster samples was evaluated by sieve analysis. For this, sieves ranging from 125 µm to 6300 µm were used (Table 4). While there is no aggregate over 1000 µm in mortar (Samples 1–3) and plaster (Examples 4–6) samples, coarse aggregate and a more homogeneous distribution are observed in plasters at a lower rate than mortars.
Mortar and plaster samples were examined in terms of matrix (binder) and aggregate properties (mineral/rock type, structure, distribution, size, orientation) by thin-section optical microscope analysis. Mortar samples are of different petrographic characteristics. 3 mortar samples belonging to the building were classified in 3 different groups and 3 plaster samples were classified in 2 different groups (Table 5a,5b). Optical microscope examinations revealed that the plaster samples have a two-layered structure. A high amount of binder was determined in the petrographic structures of the mortar and plaster samples, supporting the loss of ignition and calcination analysis (Table 5a). The matrix total binder (%TB) content of the mortar samples varies between 87–91% and in plasters between 90–97% (Table 5a). The upper layers of the plaster samples contain higher aggregates than the lower layers (Table 5a). Lime constitutes the binding structure of the mortar and plaster samples, all of which have unique characteristics (Table 5b). There are brick fragments at the rate of 1% of the total aggregate in the aggregate structure of the upper layers of Sample 3 from the mortar samples, and Sample 4 and Sample 5 from the plaster samples. In addition, organic additive parts (at the rate of 1% of the total aggregate) were determined in the structure of the lower layers of the same plaster samples (Table 5b). Mortar samples are richer in aggregate content than plaster samples. The rounded structure of the aggregates in the mortar samples indicates that the original application was made using aggregates from the stream bed. On the other hand, rounded and broken/angular aggregates are found together in plaster samples. Aggregate dimensions are indicated on thin-section optical microscope microphotographs with a measuring stick (1000 µm).
The rock structures were determined by petrographic examinations of the stone samples (Sample 7.8) sampled from the building (Table 5c). Accordingly, Example 7 has limestone (sparitic texture) and Example 8 has travertine type ski structure. Travertine in the rocks presents a more porous structure than the sample limestone (Table 5c).