对冻融环境下混凝土试样进行了不同加载速率下的单轴压缩试验,得到了混凝土材料经历不同冻融循环次数下的质量损失及破损形态,分析了冻融循环下混凝土试样的全应力一应变曲线,并给出了其单轴极限抗压强度、峰值应变随加载速率的变化特征.通过运用CT细观试验的方法初步对经历不同加载速率下的试样进行了细观结构分析.试验结果表明:在相同加载率下,混凝土单轴动态极限抗压强度随冻融循环次数的增加而降低;在相同冻融循环次数下,混凝土单轴动态极限抗压强度随加载速率的增大而提高;冻融循环作用下,在低加载速率下,混凝土试样破坏时,裂纹数目较少,主要沿砂浆和交界面处扩展,破坏时呈现出集中式的分布;而在高加载速率下,裂纹逐渐变得分散,破坏时呈现弥散状分布式的裂纹,随着加载率的提高,裂纹穿过骨料的现象增多,骨料破坏数目呈指数形式增长.以此,通过试验系统地研究了冻融循环下混凝土动态破损机理.%The concrete specimen under freeze-thaw environment was experimentally studied through uniaxial compression test with different loading rates.The mass loss of specimen was measured after different freeze-thaw cycles.The complete stress-strain curve of specimen was analyzed.And the variation characteristic of uniaxial compressive strength,peak strain varying with loading rate was given.A preliminary study on the meso-structure of specimen with different loading rates was analyzed by the application of CT technology.The results indicate that the dynamic ultimate compressive strength decreases with the increasing of freeze-thaw cycles under the same loading rates,and that the dynamic ultimate compressive strength raises with the increasing of loading rates under the same freeze-thaw cycles.Cracks appearing in these specimens under low loading rates are less and propagate mainly along the weak interface,which present centralized formation.On the contrary,cracks gradually become scattered at high loading rates,which become reticular formation as well.The cracks penetrate the aggregates evidentially increase with loading rates and the number of aggregating fracture increase at exponential speed.Based on the above data,the dynamic damage mechanism of concrete was systematic studied under freeze-thaw cycles.
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