冻融循环对混凝土静动力特性的影响

为了解冻融循环对混凝土材料静、动态力学性能的影响规律,在清水和盐水中采用"快冻法"对C60混凝土进行了不同冻融次数后的单轴静压试验和霍布金森压杆冲击试验,分析了混凝土强度变化的原因。试验表明,清水和盐水条件下,混凝土试件的质量损失和相对动弹性模量的损失率随冻融次数的增加而增大,盐水环境中更明显。清水环境下的冻融循环对混凝土的静态抗压强度具有显著影响,但对其动态抗压强度影响不明显;盐水环境下,当冻融次数较少时,混凝土的动态强度表现显著的应变率效应且不受冻融循环次数的影响,但在冻融循环次数达到240次时,混凝土的动态强度显著下降且对冲击速度不再敏感。不同冻融环境对混凝土静、动态强度影响的差异显著。

Effects on static and dynamic characteristics of concrete due to freeze-thaw cycles

To investigate the influence of freeze-thaw cycles on static and dynamic mechanical properties of concrete, a series of uniaxial static compression tests and split Hopkinson pressure bar(SHPB) impact test of a C60 concrete after different times of freeze-thaw cycles were carried out with the "quick freezing method" in plain water and salt water respectively, and the reasons for the changes of concrete strength were analyzed. Tests show that the loss of mass and the loss ratio of relative dynamic elastic modulus of concrete specimens increase with the times of freeze-thaw cycles both in plain water and in salt water, which is more obvious in salt water. In the plain water environment, the freeze-thaw cycles decrease the static compressive strength of concrete significantly,while it has less influence on the dynamic compressive strength of concrete. In the salt water environment, significant strain rate dependency is observed on the dynamic strength of concrete after freeze-thaw cycles,while the dynamic compressive strength itself is affected little by the freeze-thaw cycles of fewer times.Nonetheless, the dynamic compressive strength decreases obviously with the times of freeze-thaw cycles when the cycle times is greater than 240 and it seems no longer sensitive to the impact velocity, indicating a great difference in the effects of different freeze-thaw conditions on the static and dynamic strength of concrete.