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ANALYSIS OF FREEZE-THAW DETERIORATION AND DAMAGE CHARACTERISTICS OF EXISTING CRACKED CONCRETE
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摘要: 采用预制裂缝的方法模拟实际工程中带裂缝混凝土,研究带裂缝混凝土在冻融循环条件下的损伤劣化过程及力学特性。通过对有、无预制裂缝的混凝土试件冻融循环后的表面变化观测、单轴压缩与弹性模量试验,研究冻融循环作用对有、无预制裂缝混凝土试件的弹性模量、轴心抗压强度、应力-应变关系的影响,得到了峰值应力与峰值应变随冻融循环次数的变化关系,结合损伤力学的方法分析预制裂缝对混凝土抗冻性能的影响。结果表明:无裂缝试件在冻融后出现成片剥落、边缘缺角的表面变化,而预制裂缝试件在此基础上还出现了预制裂缝沿径向扩展、侧面萌生横向裂缝的现象;预制裂缝混凝土试件强度和弹性模量的损失率更大,得到了预制裂缝试件峰值应力与冻融循环次数的计算式;裂缝使混凝土损伤率大于无预制裂缝试件。Abstract: The pre-crack method was used to simulate the cracked concrete in the actual engineering. The damage degradation process and mechanical properties of the concrete with cracks under freeze-thaw cycles were studied. Through the observation of surface change, uniaxial compression and elastic modulus test of concrete specimens with and without pre-crack to study the freeze-thaw cycles effected on the elastic modulus, axial compressive strength, stress-strain relationship of specimens with and without pre-crack, the relationship between peak stress and peak strain as a function of freeze-thaw cycles was obtained. Combined with the damage mechanics, the effects of pre-formed cracks on the frost resistance of concrete were analyzed. The results showed that, after freezing and thawing, the crack-free specimens appeared flaking of surface and corner cutted. The phenomenon of radial propagation of pre-cracks and lateral initiation of transverse cracks appeared in pre-crack specimens. The loss rate of strength and modulus of elasticity of precast cracked concrete specimens were faster. The formulas for calculating peak stress and freeze-thaw cycles of pre-crack specimens were obtained. The cracks caused the concrete damage rate to be greater than that of the specimens without pre-crack.
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