Experimental Study On Mechanical Properties And Damage Evolution Of Concrete Under Freezing-thawing Cycles

Concrete as a common kind of polyphase and compound material, because of its many advantages, is widely used in engineering field. Studies have s hown that steel corrosion, freezing-thawing cycles and physical and erosion environment of physical chemistry are the three important factors influencing the durability of concrete. The influence of the freezing-thawing cycles of concrete durability obtained more and more attention. Especially in cold regions of west C hina, freezing- thawing cycle is the main factors for leading to the damage of concrete. Therefore, further study of concrete freezing and thawing damage failure process is of very important theoretical value and practical significance.Based on the concrete materials in cold regions of west China, this treatise is a combination of freezing-thawing cycle test, macroscopic mechanical experiment and CT scan test. The mechanical properties and CT images of concrete under the freeze-thawing environment were researched. And we also simulated the thermal analysis of concrete under freezing-thawing condition by ANSYS. So the damage and deterioration law of concrete under freezing-thawing condition will be further researched from the point of macro- level and micro- level. Finally, it can provide the theory basis for major engineering freeze-thaw catastrophe prediction and prevention research in the cold region. The main content of this paper are as follows:(1) The freezing-thawing cycle experiment was conducted on the preparation of concrete. And the uniaxial compression experiments and three-point bending tests of the samples were carried out on different freezing- thawing cycles. By studying the change rule of elastic modulus, compress strength, bending strength and the stress-strain curve, the relationship of concrete between macroscopic mechanical properties and the number of freezing-thawing cycles were explored.(2) The meso fracture-damage process of concrete process were observed by CT technology under freeze-thaw environment and the meso-structure variation characteristics of concrete CT images were obtained under different freezing and thawing cycles. The meso-damage evolution process were preliminary analyzed by using digital image processing(DIP) technology, on the basis of the change of the average CT number, the relationship curve of the damage variable and the freeze-thaw cycle was established based on meso-statistical mechanics, so that the damage evolution law and fracture mechanism of concrete meso-structure were quantitative researched under the condition of freezing and thawing cycle.(3) Based on the finite element software ANSYS, the concrete under freezing-thawing cycles were numerically simulated. The temperature field cloud picture and thermal stress field cloud picture under different freezing-thawing cycles were analysed by numerical simulation. And the feasibility of numerical simulation of concrete in freezing-thawing environment is proved.