Deteriorations on Historical Buildings Due To Capillarity; Aksaray Sultanhanı Caravansary Model

Assist. Prof. Dr. Mustafa YILDIZ, Res. Assist. Emine YILDIZ ÖZŞAHİN, Res. Assist. Ali Sinan SOĞANCI Selcuk University, Engineering and Architecture Faculty, Campus, Konya- Abstract Unconstrained groundwater rises up through the voids between soil particles such as the water rising in a capillary tube due to water stress forces which was submerged into a container completely filled with water. This capillary rise occurs in significant large amounts for fine grained (clay, silt) soils. If the foundations of the constructions were built on such soils without taking any precautions, the groundwater would rise from foundation to the walls depending on the capillary water absorption characteristics of the foundation materials. The water on the wall surface evaporates and causes deteriorations on the wall surface in relation to the acidic property of the groundwater. In a similar way, the deteriorations on the inner and outer surfaces of the walls have occurred at Aksaray Sultanhani Caravansary in the course of time which was the most important Seljuks period building constructed in 1229 on a 4866 m2 construction area composed of clayey soil where the groundwater level was so close to the ground surface. In this study, the capillary water absorption potentials of natural construction materials of andesitic tuff and marls used in Sultanhanı Caravansary and in many historical buildings from Seljuks Period were determined, and the relationships of obtained capillary water absorption coefficients with the other physical properties of the aforementioned construction materials were investigated. Additionally, the behavior of water saturated material under freezing-thawing conditions was also researched. It was concluded that the factors considerably affecting the deteriorations on the historical buildings were high water absorption coefficients and high clay contents of the construction materials of the historical buildings. Therefore, there should be taken necessary precautions to protect these historical buildings against such problems.

Keywords: Capillarity, historical building, Aksaray Sultanhanı Caravansary, water absorption coefficient

1. Introduction The buildings constructed for various purposes should provide some certain performance criteria and sustain their functionality for a long time period. However, uncontrolled moisture negatively affects these criteria required for a good performance of a building and causes decays on wooden materials, melting of stones and corrosion on metal materials which are unfavorable influences on the structural integrity of the building and result in the deterioration of the structural members before their expected economic lives. Soil regions are the moisture sources containing various types of water that the moisture transfer from soil to building cause to increase the moisture contents of the structural members. Unconstrained groundwater rises up through the voids between soil particles such as the water rising due to water stress forces in a capillary tube submerged into a container completely filled with water. This capillary rise occurs with significant large amounts for fine grained (clay, silt) soils. If the foundations of the buildings are built on such soils without taking any precautions, the groundwater will rise from foundation to the walls depending on the capillary water absorption characteristics of the foundation materials. The water on the wall surface evaporates and causes deteriorations on the wall surface in relation to the acidic property of the groundwater. More or less water leakage between the grains of soil goes down through the deeper layers of the soil by the effect of its own weight which causes the formation of groundwater with various characteristics. Soil waters can be classified as absorbed water, collected water, groundwater and capillary water. Also there exist groundwaters in gas (vapor) forms between the air pores inside the soil (Gönül et al., 2003).

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Figure 1. Soil waters (Gönül et al., 2003)

2. Applications Providing Moisture Transfer on the Exterior Shell of the Buildings Any moisture transferring event related to the building will be possible only by a force effect or a potential difference. The heat transfer (Fourier Law) due to temperature difference between two regions and the electron transfer (Ohm Law) due to voltage difference are the well-known examples related to the aforementioned subject. Similarly, the moisture transfer also occurs in accordance with this general rule, i.e. from high moist region to low moist region (Gönül, 2000). For buildings, the moisture transfer occurs between the building itself and the soil under the building which includes soil waters in liquid or gas phases (Kumaran et al., 1994).

3. Moisture Effect on Construction Materials Water entering the building from ceilings, floors or facade surfaces leads to temperature differences on the construction materials by changing their moisture contents which results in shrinkage and volumetric deformations on the materials. The deformations due to moistening which can cause micro cracks on the construction materials are observed as 0.03% for normal density concrete, 0.001% for marble & limestone and 0.07% for sandstone. Water-entrance into the construction material and water-movement inside becomes easier by the aid of these micro cracks. In other words, the water molecules of 3.5 Ao size can easily enter into the pores and micro fissures inside the construction material and move through the pores and micro fissures depending on the applied pressure on the construction material. The direct and indirect water-entrance inside the construction material cause damages on the buildings and surface deteriorations due to molds. The air/moisture ratio at the inner spaces of the building continuously changes due to capillary water absorption that causes unfavorable influences on the construction materials and people living in that building. It is known that the inner and outer surfaces of many historical buildings have been faced with deteriorations due to moisture and capillary water effects, and especially many valuable art decorations have been considerably damaged. For previously constructed buildings, the reduction or removal of moisture-based damages related to capillary water absorption will be possible only when the water absorption coefficients of the construction materials are known (Özdemir, 2002).

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4. Sultanhanı Caravansary Sultanhanı Caravansary exists on the Konya-Aksaray Highway, 100 km to Konya City and 45 km to Aksaray City. It was constructed on a 4866 m2 area (Photo 1) by I. Aladdin Keykubat, the Anatolian Seljuks Sultan, in 1229 in order to provide the security of the historical caravan road due to its military and commercial importance. Today, Sultanhanı Caravansary is accepted as the masterwork of the architecture and stone craftsmanship of Anatolian Seljuks Period, which protected its importance during the Ottomans Period, because the caravansary was existing on the . It has separate divisions used in summer and winter months that a chalet masjid is present at the center of the summer division (Konyalı, 1974).

Photo 1. Front and side views of Sultanhanı Caravansary

4.1. Construction material and construction technique Sultanhanı Caravansary was constructed with masonry construction technique by using hewn stone construction material composed of andesitic tuff and two types of marls. In geological viewpoint, marl is a sedimentary rock formed by the simultaneous sedimentation of CaCO3 and clayey materials. The clay content between 30% - 50% is present in the structure of marl which makes it softer than limestone and easily workable. Moreover, the formation of andesite rock is based on the volcanic movements in the Tertiary and Quaternary Periods. Two types of marls containing different clay amounts have been used for the construction of Sultanhanı Caravansary. The marl type with higher clay content has been considerably affected from moisture and capillarity resulting in deteriorations on the building (Photos 2, 3, 4, 5).

Photo 2. Deterioration on marl I Photo 3. Deteriorations on marls I and II

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Photo 4. Deterioration on andesitic tuff Photo 5. Deterioration on marl II

The caravansary has been settled on a clayey-silty soil at which the groundwater level was so close to the soil surface until year 2000 and lowered to a harmless level by drainage. In winters, surface waters accumulate around the Caravansary and harmfully affect the historical building.

4.2. Abrasions on Sultanhanı Caravansary due to moistening and natural effects The historical buildings wears out due to various natural effects and are exposed to serious deteriorations if continuous maintenance is not provided. The construction materials expanding in hot summer days are naturally subjected to freezing in cold winter days that the temperature differences and these natural freezing-thawing cycles cause the materials to get fatigue and worn-out. The capillary movement of water inside the walls results in deteriorations on the construction materials. In other words, the moisture rising from soil moistens the load-carrying system of the building and the salts within moisture evaporating on the wall surface cause efflorescence all of which result in harmful effects damaging the physical and chemical structures of the building walls. The capillary rise of water has also caused deteriorations on the walls of Sultanhanı Caravansary for years (Photo 6).

Photo 6. Deterioration on the walls due to Photo 7. Deterioration due to rainwater capillary rise coming from trough

The fast non-removal of rainwater from the historical building e.g. due to a damaged roof cover allows the growth of mosses and weeds on the building surfaces and inside the building. Also the rainwater flowing through the troughs has been weathering the historical building made of soft stone for years. Moreover, the freezing event is one of the most important factors related to water which cause damages on the historical buildings. The water entering into the cracks freezes and consequently shows expansion resulting in the enlargement of the cracks and broken pieces. The weathered stones due to rainwater flowing through the troughs especially on the north facade of the building and the melted stones due to freezing-thawing cycles can be seen clearly at Sultanhanı Caravansary (Photo 7).

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5. Methodology In this study, the capillary water absorption potentials of two types of marls and andesitic tuff that were used for the construction of Sultanhanı Caravansary were investigated. Moreover, the relationships between these calculated water absorption coefficients with the other properties of the materials were also researched. While marl I with 47% clay content was having a less porous structure, marl ll with 35% clay content had a visible more porous structure (Photos 8, 9 and 10).

Photo 8. Construction material marl I Photo 9. Construction material marl II

Photo 10. Construction material andesitic tuff

Additionally, the behavior of the water saturated material subjected to freezing-thawing process was also investigated. The analyzed construction materials have been used quite widespread for years in the Central that many historical buildings sustained until today from the Seljuks Period in Aksaray and its vicinity have been constructed with marls and andesitic tuffs. 7 pieces of 5 × 10 × 2 cm, 7 pieces of 5 × 5 × 5 cm and 7 pieces of 7 × 7 × 7 cm prismatic specimens from each construction material were prepared and subjected to dry density, mass density and capillary water absorption tests in order to determine their physical properties of capillary water absorption coefficient, porosity, capillary porosity and water content in the condition of water saturation (capillary). The specimen preparation and the tests on the specimens were performed in accordance with the standards of TSE 699 – Inspection and Testing Methods of Natural Construction Materials (TSE, 1987) and TSE 4045 – Capillary Water Absorption Determination for Construction Materials (TSE, 1984) (ISRM, 1978) (ISRM, 1979). Other theoretical and experimental details related to Basic Capillarity Theory, capillary water absorption (W-kg/m2) and the determination of capillary water absorption coefficient (A-kg/m2) are given in Collins (1962), Saydam (1973), Vos (1965), Davis (1969), Nielsen (1972), Nielsen et al. (1986), Domenica and Schwartz (1990), Witting and Lingott (1992), Volwein (1993), Atkins (1994), Hall (1994), Adan (1995), Freitas et al. (1995), Brocken and Pel (1995), Sosoro and Reinhardt (1995) and Janz (1997). Zitek and Vhylidal (2008) and Nizovtsev et al. (2007) studies are related to capillary absorption and moisture control processes.

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In capillary water absorption tests, the water absorption of dried specimens (at 105oC) was provided by leaving the largest surface areas (5 × 10 = 50 cm2) of the prismatic specimens (2 × 5 × 10 cm, 7 × 7 × 7 cm dimensions) in contact with water for 24 hours. Then, the mass of water (W) absorbed by the specimen and the time duration (t) until the constant water saturated mass of the specimen was reached were recorded (Figure 2) to determine the capillary water absorption coefficient A (kg/(m2/s0.5)) using the following equation.

W = A.t 0.5

Here W is the absorbed water amount (kg/m2) and t is the absorption period (s).

Figure 2. Capillary water test for the determination of capillary water absorption and capillary porosity

Dry density should be known to calculate the water content for each volume of mass. Therefore, the density was obtained applying the Archimedes Law by making the specimen water saturated with vacuum and weighing in air and water before making the following calculations for volume and mass density.

m − m V = air w ρ w

3 Here V is the volume of specimen (m ); mair is the weight of the water saturated specimen in air 3 (saturated with vacuum) (kg); ρw is the density of water (kg/m ); ρ is the density of the specimen 3 (kg/m ); mw is the weight of the water saturated specimen in water (saturated with vacuum) (kg); and mo is the oven-dry mass of the specimen (kg). The weights in air and water provide the calculation of porosity P(m3/m3), while the dry density is used for the determination of specific mass (ρs).

m − m ρ P = air 0 ρ = ρ .V s 1− P w

o Capillary porosity (Pcap) and water content in capillary saturation (wcap ) were determined for 105 C dried specimens that were subjected to one-way water absorption test. Since capillary saturation is defined as fully water saturated, the capillary porosity is also defined as water saturated porosity (Janz, 2002). The average values of dry density (volume mass), mass density (specific mass), water absorption coefficient, porosity, capillary porosity and water content of water saturated (capillary) specimens are given in Table 1.

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Table 1. The values of dry density, mass density, capillary water absorption coefficient, porosity, capillary porosity and water content under water saturated (capillary) condition for tested materials.

3 3 A P wcap ρ(kg(m ) ρ s (kg / m ) Pcap Material 2 1/ 2 (%) (%) kg / m .s (%) Andesitic tuff 1460 2680 5,06 46 36 24 Marl I (with 47% clay content) 1890 2620 1,72 28 22 11 1860 2730 3,93 32 25 14 Marl II (with 35% clay content)

Experiments were performed to determine the resistance of water saturated (capillary) specimens against natural freezing effects. At first, in order to calculate the compression strengths of the specimens produced with andesitic tuff, marl I and marl II under natural conditions, there were produced 7 × 7 × 7 cm and 5 × 5 × 5 cm cubic specimens by cutting from natural materials. Then they were dried in the oven until the constant mass was reached, and the dried specimens were subjected to the compression test with an increasing pace rate of 10 kgf/cm2-12 kgf/cm2 (1.0 N/mm2-1.2 N/mm2) per second. The compression strength of natural construction stone was calculated as in the following.

F σ = k c A

2 2 Here σc is the compression strength of stone (kgf/cm ), (N/mm ); Fk is the maximum load at the instant of failure (kgf), (N); and A is the surface area subjected to loading (cm2), (mm2). An additional analysis to determine the reduction in compression strength of the same specimens after freezing event and the resistance against freezing was also carried out. The specimens were dried until the constant mass was reached and made water saturated under normal atmospheric conditions before placing them into the freezer. This freezing-thawing process was repeated for 25 times. Same specimens were subjected to compression tests to determine the compression strength losses given in Table 2.

Table 2: Change in compressive strength after 25 freezing-thawing cycles In Natural Condition After Freezing-Thawing Decrease in Material Process Strength σ I max(kgf/cm2) σ I max(kgf/cm2) σ I max-σ II max 5×5 7× 7 5×5 σ max σ max 7× 7 cm2 ort cm2 cm2 ort (kgf/cm2) %

cm2 Andesitic Tuff 97 105 101 88 92 90 11 Marl I 298 310 304 278 285 281 7,5 (with 47% clay content) Marl II 185 183 184 179 179 179 3,2 (with 35% clay content)

6. Discussion of Results The properties such as water absorption potential under atmospheric pressure, capillary water absorption coefficient, porosity, capillary porosity, water content in capillary saturation, dry density and mass density of andesitic tuff and two types of marls (marl I and marl II) that have been used for the construction of Sultanhanı Caravansary were determined and tabulated in Table 1. Furthermore, the free compression strength values, the resistance of water (capillary) saturated specimens against freezing effects and the post-freezing compression strength values of the specimens under natural conditions were determined and given in Table 2. The lowest and highest dry densities of the investigated construction materials were obtained for andesitic tuff (1460 kg/m3) and marl I (1890 kg/m3), respectively. The highest capillary water

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absorption (wcap) was obtained for andesitic specimen (24%) after leaving the specimens in water for 4 days under atmospheric pressure conditions. On the other hand, when the porosity values of the construction materials are examined, the porosity (P) values of andesitic specimen and marl I were found to be 36% (high) and 22% (low), respectively. 5 × 10 × 2 cm specimens were used for the capillarity tests that for the first 15 minutes the andesitic specimen became completely wet and capillarity occurred very fast. For marl I, water reached to the upper surface very fast where visible porous cavity existed and could not reach to the surface at the other face where porous cavity did not exist. For marl II, water reached to the upper surface very fast at the visible porous face, while water could only rise to the half height of the specimen (1 cm) at the other face (Photos 11, 12).

Photos 11, 12. Capillarity test (Marl I and Marl II)

The visible melting cavities on the specimens provide the fast capillary rising of water inside the specimen. The height of the test specimens was observed to be insufficient, since the 5 × 10 × 2 cm prismatic specimens became saturated during the first 30 minutes and capillarity stopped. Therefore, the capillarity (water absorption) tests were performed on 7 × 7 × 7 cm specimens. It was determined that the water absorption capacity of andesitic tuff was greater than that of others. Therefore andesitic tuff will be affected from natural effects more due to its high water absorption capacity and porosity ratio. Because the porosity ratio of marl l with high clay content is less, the water absorption capacity of marl l is lower than that of marl II with low clay content in which a more porous structure due to melting cavities occurs (Photos 13, 14).

Photo13. Marl II (high porosity) Photo 14. Andesitic tuff (fast capillarity)

Although marl I, the construction material used for the historical building, had low water absorption capacity, it was too much affected from freezing-thawing process due to its high clay content (Photo 13). The clayey stones such as marl, claystone, etc. face with volume expansion due to wetting-drying process and shrinkage due to extreme drying all of which increase the fracturing tendency of them. Therefore, problems will be met in the course of time as in Sultanhanı Caravansary, when this type of stones is used for various purposes.

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There were made experiments to obtain the resistance of the water saturated (by capillary) specimens against natural freezing effects. The specimens of 7 × 7 × 7 cm and 5 × 5 × 5 cm dimensions were used during the experiments. According to the results of the free compression tests, 11% - 7.5% strength losses occurred for andesitic tuff and marl I after the freezing-thawing process. The high clay content in marl I caused the freezing-thawing effect become higher than usual.

Conclusions In this study, the deteriorations occurred on the historical buildings of Aksaray and its vicinity due to water absorption problems of construction materials were investigated. The capillary water absorption potentials of construction materials were studied to determine the variation of capillary water absorption amount of the construction material used in historical Sultanhanı Caravansary, and the relationships of the obtained water absorption coefficients with the other physical characteristics of the materials were researched. The capillary water absorption potentials of andesitic tuff and two kinds of marls having different clay contents that have been used in the historical building were determined in this study. The factors considerably affecting the deteriorations on the historical buildings are the high water absorption coefficient and the high clay content of the construction material of the building. The clayey stones such as marl, claystone, etc. face with volume expansion due to wetting-drying process and shrinkage due to extreme drying all of which increase the fracturing tendency of them. The strength values of the specimens subjected to freezing-thawing process decreased, and additionally the deteriorations on the construction materials of the investigated caravansary can be seen clearly after the physical examination is made on the building.

Acknowledgements This paper was supported by The Coordinating Office of Scientific Research Projects of Selcuk University (BAP – Selcuk University).

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