基于核磁共振和超声波探伤技术的混凝土耐久性分析

Durability Analysis of Concrete Based on Nuclear Magnetic Resonance and Ultrasonic Flaw Detection Technology

针对核磁共振试验过程中试件尺寸受限问题,采用超声波探伤技术对混凝土内部孔隙率的变化进行表征。采用冻融循环试验加速混凝土的退化,结合超声波探伤技术测得的超声波波速和核磁共振技术测得的T_(2)谱对试件内部孔隙率的变化进行表征。研究结果表明:混凝土在冻融循环退化过程中,T_(2)谱中有三个波峰,其中表示试件内部微细小裂缝的主峰面积占总面积的80%左右。T_(2)谱中第一峰(主峰)的面积变化、混凝土的孔隙率发展与冻融循环次数呈指数关系。相对动弹性摸量评价参数(ω)与冻融循环次数、试件内部孔隙率的发展呈线性关系。采用超声波探伤技术可以用来表征混凝土内部孔隙率的发展。

In order to solve the problem of limited specimen size in nuclear magnetic resonance(NMR)test,ultrasonic flaw detection(UFD)technology is proposed to characterize the change of concrete internal porosity.Freeze-thaw cycle test was used to accelerate the degradation of concrete.T_(2) spectrum measured by NMR and ultrasonic wave velocity measured by UFD technology are used to characterize the change of concrete internal porosity.The test results show that there are three peaks in T_(2) spectrum of concrete during the degradation process of freeze-thaw cycle.The main peak area of micro cracks in the specimen accounts for about 80% of the total area.The area change of the first peak(main peak)in the T_(2) spectrum,the porosity development of the concrete and the number of freeze-thaw cycles have an exponential relationship.Relative dynamic elastic modulus evaluation parameters(ω)has a linear relationship with the number of freeze-thaw cycles and the development of internal porosity.Ultrasonic testing technology can be used to characterize the development of concrete internal porosity.