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F Amini Beiram, Ebrahim Asghari, M Hajialavi Bonab,
Volume 9, Issue 1 (6-2015)

The Kandovan village is one of the tourist attractions in East Azarbaijan province of Iran, whose rural houses were excavated within the cone-shaped pyroclastic rocks (in terms of local called keran) several hundred years ago. The present paper discusses the role of engineering geological properties of Kandovan pyroclastic rocks. Kandovan pyroclastic rocks have low resistance against weathering and erosion because their components are plagioclase minerals and pumice fragments with low resistance, welding, sorting and high sphericity and rounding. Although weathering and erosion along existing joints and fractures is the most important causative agent of cone-shaped forms but there is the possibility of further damage of rocks due to continuing these processes. High porosity of rocks has caused that their high capacity for water absorption. High water absorption percent increased sensitivity of rocks against expansion and contraction by freezing-thawing and wetting-drying cycles and low hardness and low their internal strength caused the rocks weathered and disintegrated due to environmental factors. Furthermore, the weak texture of the pyroclastic rocks have caused easy erosion of those by surface waters and wind.
Davood Fereidooni, Mohammad Hossein Ghobadi,
Volume 9, Issue 2 (9-2015)

In order to assess mineralogical composition influence on durability and strength of rocks, four samples of hornfelsic rocks were selected from southern and western parts of the city of Hamedan, west of Iran. These rock samples were subjected to mineralogical, physical and mechanical tests in the laboratory. Also, they were evaluated in 15 cycles of slake-durability testing in different pH of sulfuric acid solutions and XRD analysis. Based on the results, the type and amount of minerals, their density and hardness had an influence on the uniaxial compressive strength and the slake durability index of tested rocks. That means, presence of non-dissolved minerals such as graphite in studied rocks, decreases Unconfined Compressing Strength (UCS) but increases the slake durability index. The results of slake-durability test indicated that weight loss of the samples at initial cycles was found to be higher than the end cycles. Also, in these samples, initial minerals in the fresh samples were not exchanged by secondary minerals such as clay minerals. Therefore Hamedan hornfelsic rocks are approximately resistant when were put under accelerated chemical weathering and degradation in the laboratory and natural chemical weathering.
Mh Ghobadi, R Babazadeh,
Volume 10, Issue 1 (8-2016)

Strength and durability of sandstones and their influences from natural conditions, are the most important factors which should be considered as engineering materials. In this study, the effect of freeze-thaw and salt crystallization phenomena on strength and durability of upper red formation sandstones collected from southern part of Qazvin province was investigated. Nine specimens of sandstones (specified by A, B, C, CG, S, S1, Tr, Min and Sh) were collected from different part of studied area, then their physical and mechanical characteristics were determined. In order to assessing the effect of freeze-thaw on physical and mechanical characteristics of sandstones, 60 cycles of freeze-thaw test was performed. Also in order to investigate the effect of salt crystallization on strength of studied sandstone, sodium sulphate crystallization test (100% weight solution of Na2SO4) was carried out in 20 cycles. Physical and mechanical characteristics of sandstones such as point load index, Brazilian tensile strength, wave velocity (Vp) and weight loss were computed after different cycles. To evaluate the effect of freeze-thaw and salt crystallization phenomena on durability of sandstones, slake durability test was conducted on specimens subjected to mentioned processes and changes occurred in slake durability index in 15 cycles were investigated. Based on results obtained from current study, it could be concluded that in comparison to freeze-thaw, salt crystallization can considerably reduce the strength and durability of sandstones and deteriorate them. Also it was found that index tests such as point load index, Brazilian tensile strength, wave velocity (Vp) and weight loss can predict the behavior of sandstones in different cycles of freeze-thaw and salt crystallization tests.
Mr. Mehdi Hashemi, Dr Davood Fereidooni,
Volume 17, Issue 2 (9-2023)

In this research, the durability and deterioration of two historical stone monuments, including the Dashkasan rock temple and the historical stone inscriptions of the Sojas cemetery in the south of Zanjan province, were investigated. For this purpose, two stone block samples were selected from each historical work for laboratory study. Based on the geological investigations, the historical monuments of the Dashkasan rock temple were carved on tuffs of the Karaj Formation. According to the thin section study, the Dashkasan temple rocks composed of the crystal vitric tuff and lithic vitric tuff and the samples of the historical inscriptions of the Sojas cemetery were limestone and very fine-grained sandstone, quartz being the dominant mineral of these rocks. In terms of physical characteristics, the samples studied have medium density and porosity. In terms of durability and deterioration, all four samples were subjected to 15 cycles of the slake durability test in normal water and sodium sulphate solution. The degradation function model and half-life of all four samples were determined and analysed. The results show that all four samples have a lower slake-durability index in sodium sulphate solution than in normal water. Due to the presence of quartz in lime or clay matrix, the samples of historical stone inscriptions from Sojas cemetery have more water absorption and porosity and are more durable, and their half-life is lower than the samples from Dashkasan rock temple.

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