除冰盐环境下混凝土冻融损伤深度的试验研究

文章对除冰盐环境下混凝土的冻融损伤进行了试验研究,通过对比混凝土外观变化规律、超声设备检测结果以及混凝土触水面渗透情况来获得不同冻融循环次数下混凝土的损伤深度情况。研究结果表明,当经历20次冻融循环后,混凝土冻融损伤开始向混凝土内部扩展。当经历30次冻融循环后,混凝土冻融损伤深度向下快速发展。当经历70次冻融循环后,混凝土冻融损伤向下发展变慢。这是由于前期冻融循环造成混凝土试件顶部产生大量微裂缝足以排出由于结冰产生的开裂应力,从而减弱冻融损伤向下发展的趋势。而在实际混凝土桥梁表面由于磨损存在,冻融损伤会不断向内扩展,值得桥梁管理人员注意。另外,在90次冻融循环后,最大渗透深度达到25mm,即细观裂缝已经接近普通钢筋混凝土结构中钢筋的位置,容易引发钢筋锈蚀问题。本试验研究结果可以为北方寒冷地区混凝土桥梁的抗锈蚀设计提供依据。

Experimental study on the damage depth of concrete under freeze-thaw cycles with de-icing salt

In this paper,the experimental study on the freeze-thaw damage of concrete under deicing salt environment is carried out.The damage depth of concrete under different freeze-thaw cycles is investigated by comparing the appearance change of concrete specimens,ultrasonic detection results,and the penetration depth in the concrete specimen.The test results show that when the freeze-thaw cycle reaches 20 times,the freeze-thaw damage begins to gradually extend from surface to inside of the specimen.These extending becomes significant after 30 freeze-thaw cycles and basically stabilize after 70 freeze-thaw cycles.The reason for this is that the cracks generated by the former freeze-thaw cycles can eliminate the stress from freezing,which will weaken the damage extending into internal concrete.It is worth to note that in real concrete bridges,the damage due to freeze-thaw cycles would continuously develop into concrete because of abrasion from traffic.In addition,after 90 freeze-thaw cycles,the maximum penetration depth reaches about 25 mm,that is to say,the mesoscopic cracks have approached the position of the steel bars in ordinary reinforced concrete structures,which could lead to reinforcement corrosion.So,the test results provide a theoretical basis for the anti-corrosion design of concrete bridges in northern cold regions.