Investigation On The Mass Transport Properties Of Surface Layer And Durability Protection Technology For Concrete Members

In practical engineering,the durability problem of reinforced concrete members is mainly caused by the inward migration of the erosive medium through the concrete protective layer.Regardless of the carbonization of the concrete structure or the rustremoval of the steel bars caused by the accumulation of chloride ions,the protective layer material is the first barrier to the deterioration of the durability of the reinforced concrete structure.In order to quantitatively study and improve the durability of the concrete protective layer,the permeability of the concrete protective layer and the influence of the template material and the protective material on the structure and durability of the concrete protective layer are studied.The research content and achievements are as follows:(1)The paper samples the protective layer of reinforced concrete members,core concrete and standard-conserved concrete materials,and tests their material transport performance indicators,including intrinsic gas permeability,surface capillary water absorption rate,chloride ion migration.Coefficient and chloride ion diffusion coefficient.The results show that the intrinsic gas permeability,surface capillary water absorption rate,chloride ion mobility coefficient and chloride ion diffusion coefficient of the reinforced concrete member protective layer and core concrete are higher than the standard curing concrete specimens,and the lateral protective layer of the reinforced concrete members The transmission performance data of the four materials is significantly higher than that of the upper and lower protective layers,while the material transmission performance data of the core concrete of the reinforced concrete members is lower than that of the protective layer.In order to better analyze the material transport performance index of the protective layer,the paper linearly fits the transmission properties of the four materials.It can be seen that the correlation between the intrinsic gas permeability and the chloride ion mobility coefficient is good,and the two are The correlation of porosity is also better.This indicates that the intrinsic gas permeability and chloride ion mobility coefficient can better characterize the material transport properties of concrete compared to the surface capillary water absorption rate.When quantifying the material transport properties of actual concrete members,the intrinsic gas permeability and chloride ion mobility coefficient of the protective layer must be considered.(2)The concrete protective layer cast by template with different materials was tested.The results show that the permeable template and the wooden formwork can improve the compactness of the near surface of the concrete and reduce the capillary water absorption rate due to the water absorption performance.The influence of the template of different materials on the concrete aggregate is similar.The volume content of the aggregate is gradually increased from the surface to the inside,and the aggregate content tends to be stable at the depth of 4 mm.The permeable template has a lower water-cement ratio at the near surface of the concrete protective layer due to its better water absorption performance,so that the near surface of the protective layer has a lower porosity and at the same time increases the content of the coarse aggregate at the near surface of the protective layer.It is the effect of improving the durability of the protective layer.(3)In this paper,the freeze-thaw resistance,carbonation resistance and surface capillary water absorption properties of concrete protective layers treated with different protective coatings were compared.The results show that the silane-cement based permeable crystalline composite coating has better protection effect than the single protective material,which is second only to the polyurea coating.The polyurea coating forms a dense coating on the surface of the concrete protective layer.It is almost airtight or water-permeable,so the treated concrete protective layer has the best anticarbonization effect and freeze-thaw resistance.However,it does not improve the defects of the concrete protective layer itself,so once the destruction of the polyurea coating occurs,it is impossible to provide a protective effect.