冻融循环对混凝土力学性能的影响

EFFECT OF FREEZING-THAWING CYCLES ON MECHANICAL PROPERTIES OF CONCRETE

本文验测了冻融循环对混凝土力学性能(抗压、抗拉及抗剪强度、弹性模量、泊松系数和剪切模量)的影响,并用显微镜检验了混凝土承受不同冻融循环后的微观结构,研究了高强混凝土和普通混凝土力学性能的损伤和微观性能之间的关系.试件经受了幅度为+10℃至-30℃(+50°F至-22°F)的温度变化冻融循环0、30、60及90次.冻融循环损伤了混凝土的力学性能,冻融循环愈多,则水泥浆的裂缝愈多,沿骨料和水泥浆接触面的裂缝亦愈多,导致混凝土较大损坏.普通混凝土的水泥浆裂缝以及骨料和水泥浆接触面的裂缝均较高强混凝土的多而宽,因此普通混凝土力学性能的损伤较高强混凝土为严重.

Experimental observation on the effect of freezing-thawing cycles on mechanical properties of concrete ( compresive, tensile and shear strengths, Young's modulus, Poisson's ratio and shear modulus), and microscopic inspection on the variations in the microstructure of concrete sustained various freezing-thawing cycles are reported. The relationships btweeen the deteriorations of mechanical properties and changing in microscopic behavior of both high-strength and normal strength concrete are studied. Specimens were experienced zero, 30, 60 and 90 freezing cycles with the range of temperature change between + 10℃ and -30 ℃(+50°F and -22°F). The mechanical properties of concrete are deteriorated by freezing-thawing cycles. More freezing cycles will result more cracks in the cement paste and along the aggregate-cement paste interface, and cause more deteriorations. The cracks in the paste and at the interface between aggregate and cement paste are moreand wider for normal strength concrete than for high-strength concrete. Therefore, the deteriorations of mechanical properties are more serious for normal strength concrete than for high-strength concrete.