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Abstract

Abstract
This research aims to study the effect of temperature on bond strength in air entrained concrete and to find the effect of adding entrained air on the properties of the fresh and hardened Concrete under the influence of high temperatures of different levels (20, 200, 400, 600 ºC). These properties are compared with those for normal concrete . In case of concrete structures exposed to an unexpected fire, changes are found in the properties of the concrete constituents, These changes are evaluated to assess the performance of these concrete structures and determine whether structures are safe or not .The research work includes an experimental study of the mechanical properties of the hardened concrete , and the effect of high temperature and entrained air admixture on concrete behavior including, compressive strength, splitting tensile strength, stress – strain relationship (modulus of elasticity) and bond strength between reinforcement and concrete. The work includes four different percentage of air entrained admixture (Sika_Aer) (0, 0.5, 1.0, 1.5 %) by weight of cement. The effect of these variables on the bond stress between concrete and reinforcement as a result of tensile forces using pullout test are investigated. The Results show that the failure for reinforced concrete bond strength depends on diameter of the steel bar used (Ø10 , Ø 12 and Ø 16 mm) , heating temperature for specimens after (28) days of water curing and also depends on the amount of admixture in concrete (Sika-Aer).

Keyword: Concrete, Bond Strength, Entrained air, High temperature

Keywords