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STUDY ON UNIAXIAL DYNAMIC COMPRESSIVE MECHANICAL PROPERTIES OF FREEZE-THAW DETERIORATED CONCRETE IN FROZEN CONDITIONS
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摘要: 为研究冻融劣化混凝土冰冻状态下的动态力学性能，利用10 MN动静三轴仪对经历不同冻融循环次数（0次、10次、20次、30次、40次）的冰冻混凝土进行不同应变速率（1.0×10-5，1.0×10-4，5.0×10-4，1.0×10-3，5.0×10-3 s-1）下的单轴抗压加载试验；研究冰冻状态下混凝土的峰值应力随应变速率与冻融劣化程度的变化规律，分析应变速率及冻融劣化程度对峰值应力的敏感性特征。结果表明：相同冻融劣化程度时，随着应变速率增大，冰冻状态混凝土峰值应力增大；相同应变速率下，随着冻融程度的加深，冰冻状态混凝土峰值应力先增加后减小，其单轴抗压破坏形态无明显差异。在应变速率较小时，混凝土表面砂浆脱落严重，暴露出较多粗骨料，而应变速率较大时，其表面的主裂缝很清晰。冰冻状态下混凝土单轴抗压强度仍具有速率效应，孔隙冰晶对混凝土各组分的黏结作用随其含量的增大而逐渐转变为分离隔绝作用。冻融劣化程度对峰值应力的敏感性高于应变速率对峰值应力的敏感性。Abstract: To study dynamic mechanical properties of freeze-thaw deteriorated concrete under frozen conditions, uniaxial compressive loading tests at different strain rates (1.0×10-5,1.0×10-4,5.0×10-4,1.0×10-3,5.0×10-3 and 5.0×10-3 s-1) after different freeze-thaw cycles (0,10,20,30 and 40 cycles) were carried out with a 10 MN dynamic and static triaxial apparatus.The variation laws of peak stress with different strain rates and degrees of freeze-thaw deterioration were studied.The sensitivity of strain rates and degrees of freeze-thaw deterioration to strength was analyzed.The results showed that at the same degree of freeze-thaw deterioration,the peak stress of frozen concrete increased with increase of the strain rate;increasing with freeze-thaw degrees,the peak stress of frozen concrete increased first and then decreased, without significant difference in failure modes.The slower the strain rate was, the more serious the exfoliation of mortar was on the surface of concrete, and more coarse aggregates were exposed.When strain rates were high,the main cracks on the surface of concrete were very clear.The uniaxial compressive strength of concrete under frozen states still was of a rate effect,and the bonding effect of porous ice crystals on concrete compostion world gradually change to isolation effect with the increase of contents.The sensitivity of freeze-thaw degradation degrees to peak stress was higher than that of strain rates to peak stress.
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Key words:
- concrete /
- freeze-thaw deterioration /
- frozen condition /
- strain rate
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