Document Type : Article
Authors
1
Professor, Faculty of Technical and Civil Engineering, Imam Khomeini International University, Qazvin, Iran.
2
PhD in Structural engineering, Head of Research Group, Natural Disasters Research Institute, Tehran, Iran
3
Ph.D. Student, Civil Engineering Faculty. Imam Khomeini Intenational University, Qazvin, Iran.
Abstract
To directly measure the strength and permeability of concrete, a core should be separated from the concrete and then tested in the laboratory with destructive methods. For example, to measure the permeability of concrete by existing standards, concrete must be broken and divided into half. Also, acute conditions such as temperature cycles that concrete faces in summer can have negative effects on concrete characteristics. Therefore, in this research, using innovative tests, in addition to investigating the effect of temperature cycles (40, 80, 120 and 160 cycles) on the permeability and surface resistance of concrete at different ages, measuring the depth of water penetration and resistance Concrete is compressed without breaking it. According to the results, by using the calibration charts and the equations obtained from the methods of cylindrical chamber and friction transfer, it is possible to obtain the depth of water penetration and the compressive strength of concrete without the need to break the concrete and with a correlation coefficient of over 96%. It was also observed that the cycles of temperature changes have negative effects on the durability and surface resistance of concrete in such a way that the number of 40, 80, 120 and 160 cycles of temperature changes increases the permeability of concrete by 4.1, 8.7, and 7 12.5 and 16.5 have been equaled. Also, the acute conditions of temperature changes have negative effects on the surface resistance of concrete in such a way that the surface layer resistance of concrete has decreased by more than 44% under 160 cycles of temperature changes. Considering that the surface layer of concrete has a direct relationship with the penetration of harmful substances into the concrete, it was observed that with the increase in the strength of the surface layer of concrete, the volume of water penetration into concrete has decreased. By increasing the resistance of the surface layer by 15%, the volume of water infiltration into the concrete has decreased by about 140%.
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