Assessing the Salt-frost Scaling Resistance of High Strength Light Weight Concrete

نوع: Type: thesis

مقطع: Segment: Masters

عنوان: Title: Assessing the Salt-frost Scaling Resistance of High Strength Light Weight Concrete

ارائه دهنده: Provider: Milad Momeni Safarabad

اساتید راهنما: Supervisors: Mahmoud Nili

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr. Mohammad Shoushtari - Dr. Mehdi Hosseinian

زمان و تاریخ ارائه: Time and date of presentation: 2022/2/17- 18 at

مکان ارائه: Place of presentation: online

چکیده: Abstract: Concrete is one of the most widely used materials in the construction which is used even more day by day. In this regard, on the one hand by developing science and emerging complex structural systems and on the other hand, with growing trend of construction, the need to use new lightweight materials with better performance is obvious. Reaching this goal is important in Iran as it is located in earthquake-prone region and always had been prone to strong earthquakes. Moreover, long lifetime and more durability are considered in designing of structures, these days. Therefore, choosing materials in lightweight industry should be based on durability factors. High strength lightweight concrete is one of the proper choices which can be used in structures such as roofs of high-rise structures, deck bridges, offshore floating platforms, and precast and prestressed panels. However, the performance of high-strength lightweight concrete in cold and frigid areas, especially in the presence of deicing salts, is not fully known. For this purpose, experimental research was planned to investigate the durability of this concrete against deicing salts. 12 concrete mixtures were designed with water to cement ratio of 0.38, Silica fume (10%), slag (25%-45%) as supplementary Cementous materials and 5% air entraining agent to create intentional air bubble. The salt scaling resistance test of concrete in the presence of deicing salts was performed in accordance with ASTM C672 standard. The properties of hardened concrete such as compressive strength, electrical resistance and water absorption were evaluated for understanding concrete behavior and correlation with salt scaling. MIP and Air Void tests have also been performed to investigate the microstructure of concrete. The results of the salt scaling test indicate that lightweight concrete has a better durability performance compared to ordinary concrete in the freezing and thawing cycles caused by defrosting salts. The use of silica fume increases the compressive strength and salt scaling resistance, reduces the water absorption and significantly increases the electrical resistivity in concrete mixtures. Replacement of different amounts of slag leads to a decrease in compressive strength and salt scaling resistance, an increase in water absorption and a decrease in electrical resistivity. The use of 5% air entraining agent improved the durability properties. The use of air entraining agent and silica fume simultaneously tackled the problems related to the reduction of compressive strength of air entrained concrete and significantly improved durability properties. The results of microstructure analysis show that silica fume improves the structure of concrete and slag weakens the structure of concrete at early ages but the severity of this weakness decreased at older ages.

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