Experimental Study On Nonlinear Ultrasonic Method For Nondestructive Testing Of Hydraulic Concrete

The mechanical parameters of materials have great influence on concrete structural design.Concrete structures such as dams,piers and seashore structures always work in water environment,and the extermal water will penetrate into the concrete.The existing research indicated that the pore water in wet concrete has tremendous effects on mechanical properties of concrete.So analyzing the influence rules of pore water to concrete mechanical properties and providing accurate mechanical parameters will have great significance to structural design and safety evaluation of concrete working in water environment.Researches of wet concrete mechanical properties of under static loading are conducted in this thesis.Based on the micromechanics,compressive strength reduction of wet concrete is analyzed.The main results can be summarized as follows:(1)In order to study the effect of water content,porosity and liquid surface tension on concrete strength,uniaxial compressive strength tests of different strength concrete under different immersion time,and concrete with different air content soaking at different surface tension liquid were carried out in this dissertation.The experimental process is introduced,and the test results are also analyzed.(2)By analyzing the mechanism of various influence factors to concrete strength,it is considered that immersion liquid reducing concrete surface energy is the main factor causing the wet concrete strength decrease.Based on solid diffusion,fracture mech^iics and statistics strength theory,the moisture distribution and compressive strength of concrete under different moisture gradient are analyzed.The influence parameters on concrete strength are also discussed.(3)Based on the existed research work for wet concrete elastic modulus and considering the influences of microcrack to deflection,the elastic modulus of wet concrete under different pore porosity are calculated,the influences of microcrack density,pore water,pore porosity and water viscosity in cracks on the elastic modulusof wet concrete are taken into account in the model and the contribution of these factors to elastic modulus are also discussed.