冻融环境下地聚物混凝土和螺纹钢筋粘结性能

Bond Behavior between Steel Bar and Geopolymer Concrete under Freeze-thaw Cycles

寒冷地区临海、盐碱土壤或冰盐环境中的混凝土结构因遭氯离子腐蚀和冻融循环的共同作用使得钢筋与混凝土间的粘结性能劣化,甚至会导致构件过早失效。为了分析在冻融循环和氯离子腐蚀耦合作用下地聚物混凝土与螺纹钢筋间粘结性能的变化规律,通过拉拔试验研究了地聚物混凝土与螺纹钢筋在此环境下的粘结性能,分析了保护层厚度、盐溶液浓度和冻融次数对极限粘结强度及粘结-滑移曲线的影响。结果表明:盐冻循环和水冻循环试件与未冻融试件破坏模式相同,均为劈裂破坏;但与未冻融的试件相比,极限粘结强度总体上降低,经过50次冻融循环后,盐冻和水冻试件的极限粘结强度为未冻融试件的56%~67%和80%左右;最后,基于试验数据,提出考虑冻融次数和盐溶液浓度影响作用下地聚物混凝土劈裂抗拉强度以及极限粘结强度的拟合公式,为混凝土结构的工程应用提供理论参考。

Due to the combined action of chloride ion corrosion and freeze-thaw cycle,the bonding performance between steel bars and concrete will deteriorate,and even lead to premature failure of structures.In order to analyze the change law of bonding performance between geopolymer concrete and steel bars under the coupling action of freeze-thaw cycle and chloride ion corrosion,the bonding performance between geopolymer concrete and steel bars under the environment was studied by pull-out tests.The influences of the cover thickness of geopolymer concrete,the concentration of salt solution and the number of freeze-thaw cycles on the ultimate bond strength and bond-slip curve of the specimens were analyzed.At the same time,the decaying rule of splitting tensile property of geopolymer concrete in deicer-frosting environment was summarized.The results show that the failure mode of the specimens in deicer-frosting cycles and water-freezing cycle is the same as that of the specimens without freeze-thaw cycle.However,the ultimate bond strength is generally lower than that of the without freezing specimens.After 50 freeze-thaw cycles,the ultimate bond strength of deicer-frosting cycle and water-freezing cycle specimens is about 56%~67%and 80%of that of without freezing specimens.Finally,in order to providing reference for engineering application of concrete structures,a fitting formula for the splitting tensile strength and ultimate bond strength of geopolymer concrete considering the number of freeze-thaw cycles and salt solution concentration is proposed.