پديد آورندگان :
ماهيار، شاهين دانشگاه آزاد اسلامي واحد علوم و تحقيقات، تهران، ايران , فيروزمندي شيره جيني، بهمن دانشگاه تهران - گروه باستان شناسي، تهران، ايران , خمسه، هايده دانشگاه آزاد اسلامي واحد علوم و تحقيقات - گروه باستان شناسي، تهران، ايران
كليدواژه :
فاز , ملات , ژيپس , كلسيت , XRD
چكيده لاتين :
After the political collapse of the Sassanid Empire, a kind of national resistance against the
Arabs came into being. Tabaristan was one of those areas that the invading tribes did not have a
good chance of reaching due to its special geographical location. Inscriptions in the Pahlavi
language indicates that until the fourth century AH in some areas of Tabaristan, this language
was trusted and can be a sign of a cultural resistance of the people of this land against the Arab
invasion. According to this, The hypothesis of this research is that the study of mortar of the
remaining buildings related to the early Islamic period and its comparison with the Sassanid
period mortar can show the evolution of the mortar structure up to several centuries after the
collapse of the previous system of government. The selection of Mazandaran as the spatial
territory of this research is for the existence of three tomb towers (Figure1,2) that were built in
the fourth century AH and have two common elements, which are the structure of brick and
mortar with Kufic and Pahlavi inscriptions. Apart from these towers which are located in the
east of present-day Mazandaran, there are many castles (Table2) in these areas that a
comparative study of their mortar structure can be helpful in achieving the goal of this research.
The purpose of this study is to find the answer to the question whether after the fall of the
Sassanid Empire and the disruption of the long-standing political order of Iran, there has been a
change in the technology of mortar production and how long and in which parts of Iran this can
be done. We assume that the land of Tabaristan, as mentioned before, can be a good place to
seek this technical transformation. The laboratory method selected for the study is called XRD
analysis method. In the case of mortars and mineral powders, the XRD method is a reliable
method. The XRD method is also effective for different granulations, as all the minerals in the
mortar show an X-ray scattering pattern that is easily detectable in phase detection software. If
you need quantitative analysis of mortar, you should use complementary methods of elemental
analysis such as "SEM" or even XRF method, which is not the purpose of this study; This is
because the same quantitative standard was not used to make mortar in different geographical
areas, and only the method of construction was the same over time, which changed over time,
depending on the needs of the architects. The hardening of the mortar and its adhesiveness depend on the reabsorption of the initial crystallization water of the raw mortar. Therefore, the
use of any organic matter, whether plant material, or food additives such as egg white or egg
yolk, etc., has no effect on the chemical structure of the mortar and does not help it to harden
and stick. As a result, the use of organic matter detection methods such as "Chromatography",
UV and IR spectroscopy, etc. will not be effective in this study. According to the analysis
(Table3), it can be said that in general, the mortar of all three tomb towers, like most Sassanid
structures, is a mortar of gypsum. Among the mortar samples of the studied castles in East
Mazandaran (Table4), the predominant phase with the composition of "gypsum" has been
identified only in the samples of "Hammam Kojoor Castle", "Varazan Noor Castle" and
"Kanglo Castle". Also in all the samples in which the "gypsum" composition forms the leading
phase, we encounter the "dolomite" or "calcite" phase together with the "quartz" phases with
different crystal shapes, which are reminiscent of the same structure of Sassanid mortars.
Copper-based sulfur compounds from natural copper ores and Aluminum silicate compounds in
some samples are also due to natural impurities in the raw ore. Due to the phase diagrams and
the number of phase adaptations, it is not possible to confirm the manual addition of sand or
clay to the gypsum mortar in these samples. The results of XRD studies by the author on
samples of raw gypsum (Table5), clay and sand stones (Table6) indicate that at least throughout
the Sassanid era, the predominant mortar used in the construction of castles, palaces and Fire
temples was gypsum mortar, which according to special heating conditions, the composition of
calcite remains in the mortar and this has caused the stability of this mortar. But due to the fall
of the empire, still in the early Islamic period, we see the use of the same gypsum mortar in the
eastern regions of Mazandaran. Considering the date of construction of Sassanid tombs and
castles such as "Kanglo Castle", and the similarity of mortar composition of all these samples, it
can be concluded that the method of processing, heating and baking gypsum has not changed
from the Sassanid period to at least 400 years later in Mazandaran. It seems that the structure of
the mortar, in order to reach the next more resistant mortars, goes through a transitional period,
the evidence of which can be found in the mortar used in the three tombs of the fourth century
AH in East Mazandaran.
