Experimental Study On Degradation Mechanism Of Concrete Structures In Corrosive Environment Of Mine

Long service period and complex stress are the characteristics of concrete structures in the mine engineering. At the same time, it suffers from chemical corrosion of complex environment. Concrete material strength will be gradually deterioration in the corrosive environment of mine under the coupling effect of stress and corrosion of underground structure concrete. Concrete elements will occur in part or all of the damage when the damage accumulated to a certain extent, so as to affect the safety and service life of the structural members during operation.This paper takes Huaibei mining Limited by Share Ltd of Linhuan Coal Mine entrusted project,aiming at the special environment of the underground concrete structure in the mining area, on the basis of field investigation, experimental research, numerical analysis, theoretical analysis and numerical simulation methods are used, the mechanism of sulfate attack of concrete elements, the deterioration of strength damage, the crack evolution law, the bond degradation behavior of steel reinforcement and concrete, and the acoustic emission signal characteristics of corroded concrete in the process of compression and fracture are mainly studied. In this model, the damage process of concrete in mining area based on acoustic emission is put forward.The research contents and conclusions are as follows:(1) Artificial accelerated corrosion test of three factor four level of the concrete samples were carried out in the laboratory. The compressive strength of concrete under different corrosion conditions was tested under different initial damage, different curing age and different sulfate concentrations, and the damage degree of the concrete is defined by the compressive strength. The function relationship between the concentration of sulfate solution, initial damage, curing age and stress in the environment was established. The damage degree calculation model is given under the influence of the three factors.(2) The compressive strength of concrete at different initial damage, different corrosion solution concentration and different curing age of concrete in sulfate solution is first increased and then decreased, and the quality is to reduce and then increase. The study found that the greater the initial damage of concrete,and compression strength increased faster in the early stage of corrosion, and the greater the magnitude of the compressive strength in the late stage of corrosion. The strength of concrete of curing 28 days is higher than that of the low curing age during the corrosion period.(3) It is found that the peak load of concrete breaking moment is greatly influenced by sulfate through three point bending beam accelerated corrosion test. The peak load decreases with increasing corrosion time, at the same time, the smaller the middle elastic section of the fracture process, and more easily into the plastic zone, so as to speed up the process of fracture. Concrete notched beam specimen in different concentrations of sulfate solution immersion process, the overall performance of the fracture toughness is the trend of the first increase and then decrease, the decrease amplitude increases with increasing sulfate concentration.(4) The characteristics of acoustic emission signal in the concrete under different corrosion solution concentration, initial damage, different curing age and different immersion time were analyzed, and the acoustic emission signal characteristics of different kinds of concrete fracture processes were analyzed also.The corrosion damage factor was estimated by acoustic emission activity function, and the damage degradation equation of corroded concrete was established, and the influence of concrete damage on the mechanical properties of concrete was quantitatively described. After the initial damage of concrete in the sulfate attack, corrosion damage factor in the process of loading faster than before the initial damage to the concrete. Damage factor of initial damage concrete is faster than that of concrete without initial damage after the sulfate attack.(5) The ultimate bond strength between deformed bar and corroded concrete increases first and then decreases when reinforced concrete specimens after sulfate attack of 720 days. Reduce rate is a sustained increase with the extension of corrosion time.The ultimate bond strength of reinforced concrete specimens with imitation steel fiber reinforced concrete is higher than that of non-doped imitation steel fiber reinforced concrete.(6) Gray theory was used to predict the strength of corrosion concrete under different corrosion factors and different corrosion levels. The stress state of the corroded concrete member was analyzed by numerical simulation, and the service status of the concrete member was evaluated.