Experimental Study On Dynamic Mechanical Behavior Of Concrete Under Freezing-thawing Cycles

The rapid development of national economy and implementation of the Silk Road economic belt provide great opportunities for the construction of infrastructure of cold region,experimental study on the mechanical behavior of rock and soil engineering materials under freezing-thawing cycles has been increasingly attracted more attention in recent years.Concrete is a heterogeneous composite material having a large number of meso-cracks and other defect in the interior structure under natural conditions.As a result of the existence of these defects,interior structure of concrete specimens appear varying degradation degree of damage when saturated concrete specimens subjected to freezing-thawing cycles.In addition to the static,concrete structures of cold region will inevitably face the effect of dynamic in the course of service.Due to the dynamic characteristics of concrete compared with the statics are completely different,the research on the dynamic mechanical behavior subjected to freezing-thawing cycles has great significance to the design,construction and safe operation of concrete structures of cold region.In view of this,this paper was based on macroscopic mechanical behavior tests(uniaxial compression test and three-point bending test)and theory analysis,the influence of freezing-thawing cycles on the dynamic characteristics of concrete was researched by using CT non-destructive detection technology from the meso-level.The research works in this paper mainly focus on the following aspects:(1)Freezing-thawing test was conducted to the cube specimens and the prism specimens;the freezing-thawing damage degradation model,the quality loss and the relative dynamic elastic modulus with the increasing of freezing-thawing cycles were concluded.Base on this study,the freezing-thawing degradation models of concrete were summarized out and further revealed the damage evolution of concrete under freezing-thawing cycles.(2)Uniaxial compression test and three-point bending test were carried out respectively to the cube specimens and the prism specimens subjected to different freezing-thawing cycles,the evolution law of stress-strain curve,limit of uniaxial compressive strength,peak strain,load-displacement curve,bending strength and fracture energy under static and dynamic load were concluded.(3)A series of 2D slice images were obtained through real-time scanned to the concrete under different freezing-thawing cycles,and digital image processing technology were applied to 3D reconstruction the interior pore structure of concrete specimens subjected to different freezing-thawing cycles.The spatial distribution characteristics of interior pore structure were obtained.On the basis of the change of interior pore structure,the meso-damage evolution process were preliminary analyzed by using digital image processing technology,and it's vital for the depiction on interior structure characteristics and damage mechanism of freezing-thawing damage concrete.(4)A series of 2D slice images were obtained through real-time scanned to the concrete specimens subjected to different load rates under freezing-thawing cycles.Based on the 2D slice images,digital image processing technology was applied to obtain the change of interior meso-structure characteristics under different freezing-thawing cycles.The dynamic damage mechanism was researched from meso-level,and a new method for research the dynamic damage mechanism under freezing-thawing was created.