عنوان مقاله [English]
A significant portion of the Karaj Formation in Alborz region is made of tuffs. Tuffs are readily used as construction material in various types of structures in Tehran and its neighboring provinces. The current research studies the petrographical characteristics as well the physical and mechanical characteristics of tuff samples collected from the Karaj Formation in the northern parts of Tehran, Alborz, and Qazvin provinces.
In order to study the effect of freezing and thawing on the tensile strength, an 80-cycle freezing and thawing test was performed on the samples. The Brazilian tensile strength was evaluated during difference cycles. Subsequent to the freezing and thawing test, during cycles 15, 30, and 60, a slake durability test was attempted for five cycles.
Based on the observed data, the long-term durability of tuffs was evaluated using the decay function model. The result yielded from the parameters of decay function model (decay constant and half-time) during the slake durability test were compared to those of descriptive observations during the experiment. The results indicate that the Slake durability indicator cannot be used to evaluate the decay constant and the half-time of the samples being studied.
The decay constant and the half-time yielded through the Brazilian tensile test at different cycles of the freezing and thawing experiment indicate that the decay rate of the samples were not uniform throughout samples. It is recommended, here, that the varying rate of decay should be taken into considerations when samples are chosen for specific applications.
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