摘要: |
通过单面冻融试验,研究了介质和冻融循环次数对混凝土抗冻性能和微观孔结构的影响规律.使用盒维数建立了混凝土单面冻融循环后的孔径分布分形模型,分析了分形维数与抗压强度的关系,建立了基于复合孔参数、分形维数的多因素抗压强度模型.结果表明:在不同冻融介质条件下,混凝土表观形貌、质量损失、相对动弹性模量、抗压强度、抗冻耐久性系数和孔参数随着冻融循环次数的增加逐渐劣化,盐冻对混凝土损伤程度大于水冻;混凝土孔径分布分形维数随着冻融循环次数的增加逐渐减小;在单面冻融循环过程中,混凝土孔参数演化分为初期、中期、后期3个阶段,中、后期对冻融循环作用较敏感的孔参数分别为气孔平均弦长和气孔比表面积、含气量和气孔间距系数;多因素抗压强度模型与复合孔参数、分形维数之间的回归效果显著,可以准确地描述水、盐单面冻融循环前后混凝土抗压强度与孔结构的定量关系. |
关键词: 混凝土 单面冻融循环 孔结构 分形维数 抗压强度模型 |
DOI:103969/j.issn.1007 9629202006010 |
分类号: |
基金项目:国家自然科学基金资助项目(11762015,11362013) |
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Modeling of Compressive Strength of Concrete Based on Pore Structure under Single Side Freeze Thaw Condition |
ZHAO Yanru1, LIU Fangfang1, WANG Lei1, GUO Zilin2
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1.School of Civil Engineering, Inner Mongolia University of Technology, Hohhot 010051, China;2.Shandong Tongyuan Design Group Co., Ltd., Jinan 250000, China
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Abstract: |
The effects of different freeze thaw media and freeze thaw cycles on the freeze thaw resistance and pore structure of concrete were studied through the single side freeze thaw test. Based on the box dimension, the fractal model of the pore size distribution of concrete after freeze thaw cycles was established, and the relationship between the fractal dimension and compressive strength was analyzed. Finally, a multifactor compressive strength model based on compound pore parameters and fractal dimension was established. The results show that the surface morphology, mass loss, relative dynamic elastic modulus, compressive strength, frost durability coefficient and pore structure parameters of concrete under different freeze thaw media gradually deteriorate with the increase of freeze thaw cycles, and the damage of the concrete in salt solution is more serious than in water. The fractal dimension of concrete pore distribution decreases with the increase of freeze thaw cycles. The evolution of pore structure parameters of concrete in the process of the single surface freeze thaw cycle can be divided into three stages:initial stage, middle stage and late stage. The pore parameters which are sensitive to freeze thaw cycle in middle and late stages are average chord length, specific surface area, air content and spacing factor. The regression effect of the multi factor compressive strength with the parameters of the composite pore structure and the fractal dimension is significant. The model can accurately describe the quantitative relationship between the compressive strength and the pore structure of concrete either in water or salt solution after the freeze thaw cycle. |
Key words: concrete single side freeze thaw cycle pore structure fractal dimension compressive strength model |