硫酸盐侵蚀作用下混凝土细观破损机理研究
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摘要
侵蚀环境下混凝土材料的内部孔隙空间分布特征与演化规律是材料破损机理及宏观力学性能研究的关键问题。采用X射线断层扫描技术(CT)对硫酸盐侵蚀与干湿循环耦合作用下混凝土的细观损伤过程进行实时扫描,在此基础上,结合图像处理与三维重构技术开展了混凝土内部孔隙结构的空间分布特征与演化规律研究,并通过提出的孔隙分区的方法深入研究了材料细观破损特征和机理。结果表明:宏观上试样质量、抗压强度均呈现规律性变化,溶液中钙镁离子浓度有明显的累积性趋势;细观上试样孔隙率随侵蚀时间的增加呈先减小后增大的变化,单轴抗压强度与孔隙率大体上呈负相关关系。同时,混凝土试样不同分区内孔隙率演化规律各不相同,但总体呈现先减小后增大的趋势,侵蚀作用深度随侵蚀时间不断增长。结论可为深入研究硫酸盐侵蚀下混凝土材料细观破损机理提供依据。
The evolution and spatial distribution of internal random meso-porous structure are key problems in studying damage mechanism and macro-mechanical properties of concrete material under sulfate attack.X-ray tomography(CT)were used to scan the meso-damage process of concrete under sulfate attack.Based on this,combined with image processing and 3 Dreconstruction technology,the spatial distribution characteristics and evolution laws of pore in concrete was investigated using the proposed method of pore partitioning.The experimental results show that the concentration of Ca2+and Mg2+in the solution increased slowly.The compressive strength of concrete is closely related to its meso-pore structure under the coupling of sulfate attack and drying-wetting cycles.The evolution laws of pore in different regions of concrete specimen are different under the coupled effect of sulfate attack and drying-wetting cycles.Generally,the porosity increased after a slight decrease,and the corrosion depth increases with the corrosion time.There was a negative correlation between the uniaxial compressive strength and porosity.This study laid foundation for further research on meso-damage mechanism of concrete under sulfate attack.
The evolution and spatial distribution of internal random meso-porous structure are key problems in studying damage mechanism and macro-mechanical properties of concrete material under sulfate attack.X-ray tomography(CT)were used to scan the meso-damage process of concrete under sulfate attack.Based on this,combined with image processing and 3 Dreconstruction technology,the spatial distribution characteristics and evolution laws of pore in concrete was investigated using the proposed method of pore partitioning.The experimental results show that the concentration of Ca2+and Mg2+in the solution increased slowly.The compressive strength of concrete is closely related to its meso-pore structure under the coupling of sulfate attack and drying-wetting cycles.The evolution laws of pore in different regions of concrete specimen are different under the coupled effect of sulfate attack and drying-wetting cycles.Generally,the porosity increased after a slight decrease,and the corrosion depth increases with the corrosion time.There was a negative correlation between the uniaxial compressive strength and porosity.This study laid foundation for further research on meso-damage mechanism of concrete under sulfate attack.
引文
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[12]Bera B,Mitra S K,Vick D.Understanding the micro structure of Berea Sandstone by the simultaneous use of microcomputed tomography(micro-CT)and focused ion beam-scanning electron microscopy(FIB-SEM)[J].Micron,2011,42:412-418.
[13]Yuan J,Liu Y,Tan Zh Ch,et al.Investigating the failure process of concrete under the coupled actions between sulfate attack and drying-wetting cycles by using X-ray CT[J].Construction and Building Materials,2016,108:129-138.
[14]Qian Ch X,Nie Y F,Cao T J.Sulphateattack-induced damage and micro-mechanical properties of concrete characterized by nano-indentation coupled with X-ray computed tomography[J].Structural Concrete,2016,17(1):96-104.
[15]田威,张鹏坤,谢永利,等.冻融环境下基于CT技术的混凝土内部孔隙结构的三维动态量测与分布特征研究[J].长安大学学报(自然科学版),2016,36(3):48-54.Tian W,Zhang P K,Xie Y L,et al.3Ddynamic measurement and distribution characteristics study on the concrete porous structure under freeze-thaw environment based on CT technique[J].Journal of Chang’an University(Natural Science Edition),2016,36(3):48-54.(in Chinese)
[2]高润东.复杂环境下混凝土硫酸盐侵蚀微-宏观劣化规律研究[M].北京:清华大学,2012.Gao R D.Micro-macro degradation regularity of sulfate attack on concrete under complex environments[M].Beijin:Tsinghua University,2012.(in Chinese)
[3]Niu D T,Wang Y D,Ma R,et al.Experimentstudy on the failure mechanism of dry-mix shotcrete under the combined actions of sulfate attack and drying-wetting cycles[J].constructions and building materials,2015,(81):74-80.
[4]Jiang L,Niu D T.Study of deterioration of concrete exposed to different types of sulfate solutions under drying-wetting cycles[J].Constructions and Building Materials,2016,(117):88-98.
[5]Yu D M,Guan B W,He R,et al.Sulfate attack of Portland cement concrete under dynamic flexural loading:A coupling function[J].Construction and Building Materials,2016,115:478-485.
[6]梁咏宁,袁迎曙.硫酸钠和硫酸镁溶液中混凝土侵蚀破坏的机理[J].硅酸盐学报,2007,35(4):504-508.Liang Y N,Yuan Y Sh.Mechanism of concrete destruction under sodium sulfate and magnesium sulfate solution[J].Journal of the Chinese Ceramic Society,2007,35(4):504-508.(in Chinese)
[7]王海龙,董宜森,孙晓燕,等.干湿交替环境下混凝土受硫酸盐侵蚀劣化机理[J].浙江大学学报(工学版).2012,46(7):1 255-1 261.Wang H L,Dong Y S,Sun X Y,et al.Damage mechanism of concrete deteriorated by sulfate attack in wetdry cycle environment[J].Journal of Zhejiang University(Engineering Science),2012,46(7):1 255-1 261.(in Chinese)
[8]Suleiman A R,Soliman A M,Nehdi M L.Effect of surface treatment on durability of concrete exposed to physical sulfate attack[J].Construction and Building Materials,2014,73:674-681.
[9]Okochi H,Kameda H,Hasegawa S I,et al.Deterioration of concrete structures by acid deposition-an assessment of the role of rainwater on deterioration by laboratory and field exposure experiments using mortar specimens[J].Atmospheric Environment,2000,34(18):2 937-2 945.
[10]Kanazu T,Matsumura T,Nishiuchi T,et al.Effect of simulated acid rain on deterioration of concrete[J].Water Air&Soil Pollution,2001,130(14):1 481-1 486.
[11]金祖权,孙伟,张云升,等.混凝土在硫酸盐、氯盐溶液中的损伤过程[J].硅酸盐学报,2006,34(5):48-54.Jin Z Q,Sun W,Zhang Y Sh,et al.Damage of concrete in sulfate and chloride solution[J].Journal of the Chinese Ceramic Society,2006,34(5):48-54.(in Chinese)
[12]Bera B,Mitra S K,Vick D.Understanding the micro structure of Berea Sandstone by the simultaneous use of microcomputed tomography(micro-CT)and focused ion beam-scanning electron microscopy(FIB-SEM)[J].Micron,2011,42:412-418.
[13]Yuan J,Liu Y,Tan Zh Ch,et al.Investigating the failure process of concrete under the coupled actions between sulfate attack and drying-wetting cycles by using X-ray CT[J].Construction and Building Materials,2016,108:129-138.
[14]Qian Ch X,Nie Y F,Cao T J.Sulphateattack-induced damage and micro-mechanical properties of concrete characterized by nano-indentation coupled with X-ray computed tomography[J].Structural Concrete,2016,17(1):96-104.
[15]田威,张鹏坤,谢永利,等.冻融环境下基于CT技术的混凝土内部孔隙结构的三维动态量测与分布特征研究[J].长安大学学报(自然科学版),2016,36(3):48-54.Tian W,Zhang P K,Xie Y L,et al.3Ddynamic measurement and distribution characteristics study on the concrete porous structure under freeze-thaw environment based on CT technique[J].Journal of Chang’an University(Natural Science Edition),2016,36(3):48-54.(in Chinese)