Study On Performance Deterioration Law Of Hydraulic Concrete Under Multi-factor Coupling

Study on durability of concrete structures is an important aspect in the research field of materials science. As concrete structures are widely used and the environmental conditions are increasingly severe, the harmfulness of concrete structures are affected by environment is also increased, and the length of the engineering life on concrete structure is determined by the severe degree of environmental conditions. In the west of China, the existing irrigation districts are mainly distributed in the inland river basin and the loess plateau region. Its special climate and geographical environment as well as the flood irrigation have caused the water-salt transfer and variation of groundwater level, which leads the hydraulic concrete structures in irrigation districts suffering carbonation, corrosion, and dry-wet cycles, and the speed of damage and deterioration is significantly higher than other areas in China. Concrete structures may suffer from a variety of complex environment in the practical use process, so study on deterioration law of concrete need to be more close to the practical use environment, where concrete structures are not only subjected to damage under sulfate attack, carbonation and dry-wet cycles, but are affected by gravity itself, design water level, increased water level, the crowd, wind, earthquake and other environmental factors. So study on deterioration law of concrete under multi-factor coupling has far-reaching significance.The hydraulic concrete material and u-shaped aqueduct were taken as the typical study object.the study methods of field investigation, X ray diffracmeter,indoor accelerated test and theoretical analysis were used to carry out the research of performance degradation law under carbonation, corrosion, and dry-wet cycles.Segmental parameters got from indoor accelerated test were extracted, the three-dimensional finite element software ANSYS was used to analysis the stress and deformation law of aqueduct structure under the different condition combination. The main contents were as follows:(1)The actual construction requirements of hydraulic structures and engineering application of concrete mix proportion of high performance were considered in the irrigation, structure specimen of the different mixing proportion were designed, and the erosive concrete residue was attrited for the X-ray diffraction experiment to determine the main erosive ion of concrete structures. Reasonable corrosion environment and system were selected to simulate the local corrosion environment of concrete suffered and study the damage and deterioration process.(2)Based on the experimental data and theory analysis,the mass loss rate and relative dynamic modulus of elasticity were regarded as evaluation indexs,and the impacts of erosion pattern,water-cement ratio and adulterate amount of coal ash and mineral powder on performance degradation of concrete durability were studied to explore nature of concrete deterioration.(3)The related experiment data were extracted, and the material properties such as elastic modulus and unit weight of reinforced concrete in aqueduct were dealt with equivalently. The structure of the aqueduct was analyzed to study the various stress and deformation law under the different load combinations before and after the frame of aqueduct suffered coupling damage.Research results show that carbonation make concrete surface layer change dense, but make degradation speed of concrete material accelerate due to changes of chemical composition.Anti-sulfate corrosion performance can reach relatively optimized state with the addition of 20% fly ash, and concrete with low water cement ratio can more effectively prevent erosion ion from penetrating the concrete structures than high water cement ratio. After the frame of aqueduct suffers the multi-factor coupling damage, the increase of tensile stress, shear stress and displacement are more likely to make local concrete structures appear cracking phenomenon.Especially in the coupling part, the growth range of the stress and displacement is so big that the concrete part is easy to produce cracks. Research results will provide a reference for research paradigm on durability of concrete, and provide theoretical basis for the aqueduct structure design and maintenance in operation process.