Study Of Multiple External Effects On Concrete Degradation Underexternal Sodium Sulfate Attack

Sulfate is widely found in the soil and water.Concrete structure has long been in the sulfate environment,which can lead to the deterioration of the mechanical properties of the concrete material and even the expansion and destruction.The engineering examples that have been damaged by the erosion of the sulfate are in common,and the corrosion of the concrete.The effect has become one of the major environmental impacts of structural durability,especially for sodium sulfate.The process of sodium sulfate attacking concrete is complicated,involving the mass transfer process of the external sodium sulfate into the concrete,and the chemical reaction of the concrete itself produces the swelling material.As the above process progresses,any change will take place in the concrete itself.The distribution of the external sodium sulfate based on the mass transfer process and the chemical reaction process is the key to deeply understand the deterioration of the mechanical properties of the sodium sulfate attacked concrete and the evolution of the damage.The improved barium sulfate weight method was used to evaluate the sulfate ion concentration of concrete and cement with different sulfate attacked ages.Then the diffusion law of sulfate ion in mortar and concrete was analyzed.The dynamic compressive and bending tests were carried out to study the influence of sulfate attack on the dynamic properties of cement and concrete.The compressive strength of attacked mortar is increased with the increasing strain rate and the strain rate effect of attacked mortar will experience a significant variation with the growth of attacked time.Based on the COMSOL software platform,the model under different working conditions is solved by different time nodes,and the concrete specimen under the corresponding time node under this specific working condition is used to carry out sulfuric acid.The results of the model are compared with the experimental results.It is proved that the theoretical model is reliable and compared with the existing model,which shows that the model is closer to the real distribution.On the basis of this,the present model is revised and the results of several typical variable working conditions(erosion solution temperature,erosion solution concentration,p H of etching solution,concrete grade)in the actual erosion environment are analyzed by changing the corresponding factors in the theoretical model.The above experiments verify the theoretical results under various operating conditions and analyze the differences.