عنوان مقاله [English]
The historical site of Rab-e Rashidi of Tabriz or Rashidieh of Tabriz, which was built in 700 AH and It was used until the tenth century AH. It has been exploited in various residential and military ways. One of the architectural structures of Rab-e Rashidi is its large tower, which is located on the southern front. According to preliminary studies of this structure it has built in the tenth century AH. The engineering structure of the Rab-e Rashidi has not yet been studied archaeologically from a technological point of view. In particular, this large tower, contrary to the common architecture of the eighth to tenth centuries AH in Iran, especially Tabriz, is made of stone materials. It is natural that the knowledge of construction technology and technology used in this tower, which is contrary to similar buildings of the seventh to tenth centuries AH, requires the adoption of archaeological studies of technology and structure. This study is to review those examples of studies whose process can be repeated experimentally. Therefore, the mortar technology used in this tower, which has fully survived it from the severe earthquakes of the Safavid and early Qajar periods in Tabriz, needs to be re-recognized by scientific methods including field and laboratory studies and analytical and experimental. In this study, five mortar samples were prepared from five different points of the tower and studies of XRD, XRF, SEM, FTIR, petrography and digital microscope were performed. As a result of the studies, it was found that lime mortar was used in all parts of the tower, from the foundation to the upper parts made of stone. Some sand is used in lime mortar and there is a small amount of soil. Contrary to popular belief, no gypsum was detected in the mortar composition.
Keywords: Technology Archeology, Structure, Mortar, Rab-e Rashidi, Tabriz.
Mortar in historical buildings is one of the most important topics in the field of archeology in cultural heritage. Due to the climate as well as the mines in the area, suitable mortar and construction materials have been selected and used in the past. Building materials such as stone and brick could be used again in later periods in the new building, which has happened again and again in Iran. But mortar, due to its physical and chemical properties, can be used only once, unless it is considered as a new mortar filler. Therefore, in archaeological studies, the originality of the mortar can be further emphasized. For example, in the big tower of Rab-e Rashidi, the stone materials of the Mongol Ilkhanate period in the Safavid period have been used. Mortar that is related to the period of construction of the work (Safavid period) and a large part of stone materials and tombstones is detected for to the 8th century AH. Is.
One of the architectural structures of Rab-e Rashidi is its large tower, which is located on the southern front. This structure with a diameter of 27 and a height of 12 meters is the largest tower of the Rab-e Rashidi towers. According to initial studies it was made in the tenth century AH. It is natural that the knowledge of technology and construction technology used in this tower, which is contrary to similar examples of the seventh to tenth centuries AH, requires the adoption of technological archaeological studies, especially experimental archeology. This study is to review those examples of studies whose process can be repeated experimentally. Therefore, the mortar technology used in this tower, which has fully withstood the severe earthquakes of the Safavid and early Qajar eras in Tabriz, needs to be recognized again by scientific methods including field and laboratory studies and analytical and experimental.
Research Questions and Hypotheses: The research questions are as follows: According to the remaining parts of the Great Rab-e Rashidi Tower and relying on technical studies on the sample of historical mortars, how many types of mortars are used in this structure. What are the characteristics of the mortar used in the big south tower of Rab-e Rashidi in terms of construction technology? Research Hypothesis: It seems that the mortar used in the large southern tower of Rab-e Rashidi is of limestone and gypsum type and without additives. Also, the mortar in the depth of the structure is different from the mortar of the outer layer of the wall of the big tower of Rab-e Rashidi.
Discussion of Findings
A: Digital microscope: In ocular observation, the mortars are almost white and uniform. When the different parts of the samples were examined with a magnification of 65 times, it was observed that the mortar was not uniform in color and had different grains, textures and components.
B: Scanning electron microscope: There are two parts that can be examined in the images: the mineral part and the organic part. The mineral part shows calcite and quartz crystals which have high density in some parts and high porosity in some parts. Sometimes large grains of sand are seen in which the density of calcite crystals is higher than in other parts. In fact, it can be said that if there is a significant amount of sand with a uniform distribution in calcareous mortar, the strength of the mortar is higher than normal (without sand). The second part to consider is the organic part, which is related to microorganisms. The growth of the fungus and its penetration into the structure of the mortar is quite evident.
A: XRD analysis: The analysis revealed that the main phases identified are: Calcite, Quartz, Albite and Orthoclase. D: XRF analysis: As a result of the analysis, it was found that the oxide composition of the identified elements are: SiO2, CaO and Al2O3.
E: Petrography: Five samples have heterogeneous texture and different minerals such as quartz, sandstone, siltstone, plagioclase, igneous rock fragments, metamorphic rock fragments, limestone, calcite mineral fragments and ferrous clay compounds in the sample matrix they are seen as fillers and inclusions. The dough composition or matrix of the samples is carbonate. The studied samples are almost identical and their main difference is in the percentage of frequency of each of the above mentioned materials.
Contrary to previous assumptions that more than one type of mortar was used in the construction of this tower, based on laboratory studies, it was found that in all parts of the tower, including the foundation, the inner structure of the tower and its outer part one types of mortar were used in terms of structure and materials. Due to the location of the mortar used and the conditions it has had throughout history, there have been slight changes in the structure of the mortar that have actually eroded somewhat. For example, foundation mortar has become a breeding ground for microorganisms due to its relatively high humidity conditions, lack of air under the soil, and lack of light. Fungi and other microorganisms have grown and entered the structure of the mortar, and over time, the strength of the mortar has decreased. Also, based on technical studies conducted on the mortar samples of Rab-e Rashidi Tower, it can be said that besides lime, which is the main material of mortar, there are also impurities. One of the reasons for the strength of mortar is the use of coal powder and sometimes ash in the structure of the mortar. Also the other reason for the strength of mortar is the reaction of lime with silicon.