Experimental Research And Numerical Analysis Of Freeze-thaw Failure Law Of Reinforced Concrete With Different Corrosion Rate

Under the influence of ice,snow and other harsh natural environments,reinforced concrete buildings in Northeast,Northwest and other regions of my country often suffer damage caused by freeze-thaw,and freeze-thaw damage occurs after the damage accumulates.In addition,the steel structure will corrode in a humid environment,and the two will have a huge impact on the safety and stability of the reinforced concrete structure.At present,most researchers mainly study the corrosion and freeze-thaw of reinforced concrete from the macro level,and there are relatively few studies under the combined effect of the two.The macro-level research ignores the nature of the heterogeneous concrete material,which is not sufficient to fundamentally explain its failure mechanism.Based on this,this paper starts from the meso-level and regards reinforced concrete as a heterogeneous composite material composed of steel bars,aggregates,mortar,and the interface layer between the aggregate and mortar,and prepares three groups of different corrosion levels.For reinforced concrete specimens,the freeze-thaw cycle damage law of corroded reinforced concrete was studied through a combination of indoor experiment and numerical simulation.The research content and main conclusions are as follows:(1)Observe the largest cracks of reinforced concrete specimens with different degrees of corrosion and different freeze-thaw cycles after corrosion.The results show that within the range of the degree of corrosion and the number of freeze-thaw cycles conducted in this paper,as the degree of corrosion and the number of freeze-thaw cycles increase,the connection probability and the width of the crack on the side of the concrete close to the protective layer will increase.The degree of rust is more obvious for the increase in the probability of crack connection.(2)Observe and compare the appearance changes and quality loss rates of reinforced concrete specimens with different degrees of corrosion and different freeze-thaw cycles.The results show that the corrosion of steel bars has a significant impact on the freeze-thaw damage of reinforced concrete.The general trend is that the greater the degree of rust,the lower the frost resistance of concrete.However,it is worth noting that among the reinforced concrete specimens in the corrosion test in this paper,the frost resistance of the reinforced concrete specimens with a corrosion degree of 4% is slightly improved compared to the other two groups of corrosion specimens.Both the mass loss rate and the peeling degree of the surface mortar are smaller than the two groups of specimens with a rust degree of 3% and 5%.Analysis of the reason: the corrosion products generated at this level of corrosion will fill the micro-defects of the concrete around the steel bars to a certain extent,and the rust expansion force generated at the same time will squeeze the concrete around the steel bars,reducing the pores inside the concrete,thereby reducing the pores in the concrete.The other two sets of rusty specimens increase the frost resistance.(3)Based on the data obtained from the test and starting with the reinforced concrete meso-level,the two-dimensional random aggregate mesoscopic model is combined with the ABAQUS numerical simulation software;the corrosion expansion process of the reinforced concrete is simulated by the equivalent force loading method and The freeze-thaw cycle process of corroded reinforced concrete is numerically simulated based on the hypothesis of temperature stress.The simulation results are compared with the experimental results,and then it is proved that it is feasible to use the random aggregate model to analyze the meso-damage damage of corroded reinforced concrete under freeze-thaw cycles.The simulation found that only the failure form under the action of the rust expansion force of the steel bar is roughly "┻" shape.The freeze-thaw damage of the corroded reinforced concrete mainly expands from the outside to the inside,and gradually forms a damage form connecting the internal and external damage;the interface layer;And mortar is the most vulnerable position inside the concrete.There are 39 figures,7 tables and 54 references.