冻融环境下不同预制裂缝混凝土断裂性能研究

对不同相对切口深度的预裂缝混凝土试件进行冻融循环试验,循环次数分别为0、25、50、75、100次。对冻融循环后的试件进行三点弯曲试验,观察试件的表观变化,并利用扫描电子显微镜和立体显微镜观察试件裂缝的情况。分别从宏观力学性能、损伤劣化规律、细微观结构等方面对冻融环境下混凝土断裂力学性能进行研究,并根据混凝土的损伤理论,定义了混凝土基于微缺陷及动弹性模量的损伤变量。结果表明:混凝土冻融循环损伤是初始缺陷发展、劣化并累积的过程;混凝土断裂韧度与初始裂缝相对深度无关,与抗弯强度具有良好的线性相关性。

Study on fracture properties of different pre-crack concrete under freezing and thawing environment

The pre-crack concrete specimens with different relative incision depths were tested under 0, 25, 50, 75, and 100 times freeze-thaw cycles, respectively. A three-point bending test was performed on the test pieces after the freeze-thaw cycles, and the apparent changes of the test pieces were observed, and the cracks of the test pieces were observed by a scanning electron microscope and a stereo microscope. The fracture mechanical properties of concrete under freeze-thaw environment were studied from the aspects of macroscopic mechanical properties, damage deterioration law and fine microstructure. The damage variables of concrete based on micro-defects and dynamic elastic modulus were defined according to the damage theory of concrete. The results showed that the concrete freeze-thaw cycle damage is the process of initial defect development, degradation and accumulation. The concrete fracture toughness has no apparent relationship with the relative depth of the initial crack, but has a good linear correlation with the flexural strength.