Based on the mechanism of stray current generation in underground structures,the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete ...Based on the mechanism of stray current generation in underground structures,the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete under the action of stray current and sulphate.The deterioration law of concrete under the action of stray current and sulphate was studied by microscopic techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD).The microstructure of corroded concrete was observed to determine the phase composition of erosion products.The damage performances such as quality,strength,and dynamic elastic mode of corroded concrete were performed.The experimental results show that,under the action of stray current,the products of sulfate-eroded concrete are mainly gypsum,ettringite,and thaumasite;the stray current accelerates the hydration process of cement and the erosion of concrete by sulfate;when the concrete pores are filled with the erosion product,there is an increase of approximately 10% in the concrete compressive strength and dynamic elastic modulus;and the concrete compressive strength is more sensitive to the stray current electrification period than the current intensity.展开更多
采用Rapid Air 457气孔分析仪测试了玄武岩-聚丙烯混杂纤维增强混凝土(HBPRC)的气孔结构,分析了不同纤维添加方式对混凝土累计气孔含量和气孔表面分形特征的影响。研究结果表明,玄武岩纤维、聚丙烯纤维以及玄武岩-聚丙烯混杂纤维的掺入...采用Rapid Air 457气孔分析仪测试了玄武岩-聚丙烯混杂纤维增强混凝土(HBPRC)的气孔结构,分析了不同纤维添加方式对混凝土累计气孔含量和气孔表面分形特征的影响。研究结果表明,玄武岩纤维、聚丙烯纤维以及玄武岩-聚丙烯混杂纤维的掺入使混凝土的累计气孔含量增大了76.5%~354.1%,并且混凝土的累计气孔含量随纤维掺量的增加而增大。HBPRC的气孔结构具有明显的分形特征且其分形特征具有尺度相关性,在小孔隙区、中孔隙区、大孔隙区和超大孔隙区,气孔面分形维数(D_(S))依次增大,但在孔径大于1500μm的区域没有分形特征。随着纤维的掺入,混凝土大孔隙区和超大孔隙区的D_(S)发生了明显的变化,单掺0.1%(体积分数,下同)的玄武岩纤维或0.1%的聚丙烯纤维增大了大孔隙区和超大孔隙区的D_(S);掺入0.1%的玄武岩-聚丙烯混杂纤维对大孔隙区和超大孔隙区D_(S)的影响较小;而掺入0.2%的玄武岩-聚丙烯混杂纤维显著减小了超大孔隙区的D_(S)。通过细观分析,认为纤维形成的网络结构对混凝土拌合过程中气泡合并产生的抑制作用是HBPRC大孔隙区和超大孔隙区D_(S)增大的主要原因,而纤维的弱分散性和长时间的搅拌会导致超大孔隙区的D_(S)减小。展开更多
基金Funded by the National Natural Science Foundation of China (Nos.51590914 and 52078415)the Science and Technology Program of Shaanxi Province (Nos.2019KW-047, 20JY034, and SGSNXA00XGJS20015 60)the China Scholarship Council (No.202008610268)。
文摘Based on the mechanism of stray current generation in underground structures,the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete under the action of stray current and sulphate.The deterioration law of concrete under the action of stray current and sulphate was studied by microscopic techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD).The microstructure of corroded concrete was observed to determine the phase composition of erosion products.The damage performances such as quality,strength,and dynamic elastic mode of corroded concrete were performed.The experimental results show that,under the action of stray current,the products of sulfate-eroded concrete are mainly gypsum,ettringite,and thaumasite;the stray current accelerates the hydration process of cement and the erosion of concrete by sulfate;when the concrete pores are filled with the erosion product,there is an increase of approximately 10% in the concrete compressive strength and dynamic elastic modulus;and the concrete compressive strength is more sensitive to the stray current electrification period than the current intensity.
文摘采用Rapid Air 457气孔分析仪测试了玄武岩-聚丙烯混杂纤维增强混凝土(HBPRC)的气孔结构,分析了不同纤维添加方式对混凝土累计气孔含量和气孔表面分形特征的影响。研究结果表明,玄武岩纤维、聚丙烯纤维以及玄武岩-聚丙烯混杂纤维的掺入使混凝土的累计气孔含量增大了76.5%~354.1%,并且混凝土的累计气孔含量随纤维掺量的增加而增大。HBPRC的气孔结构具有明显的分形特征且其分形特征具有尺度相关性,在小孔隙区、中孔隙区、大孔隙区和超大孔隙区,气孔面分形维数(D_(S))依次增大,但在孔径大于1500μm的区域没有分形特征。随着纤维的掺入,混凝土大孔隙区和超大孔隙区的D_(S)发生了明显的变化,单掺0.1%(体积分数,下同)的玄武岩纤维或0.1%的聚丙烯纤维增大了大孔隙区和超大孔隙区的D_(S);掺入0.1%的玄武岩-聚丙烯混杂纤维对大孔隙区和超大孔隙区D_(S)的影响较小;而掺入0.2%的玄武岩-聚丙烯混杂纤维显著减小了超大孔隙区的D_(S)。通过细观分析,认为纤维形成的网络结构对混凝土拌合过程中气泡合并产生的抑制作用是HBPRC大孔隙区和超大孔隙区D_(S)增大的主要原因,而纤维的弱分散性和长时间的搅拌会导致超大孔隙区的D_(S)减小。
