Optimal Design Of Concrete Corrosion Prevention Under The Microbial Action Of Sewage

In recent years,the aging and deterioration of underground sewage pipe network has appeared in every big city in China.Facing the large-scale maintenance or replacement,the research on corrosion prevention and control of concrete sewage pipe is imminent.In this paper,three typical coatings and seven fungicides were selected to optimize the design.First of all,the coating's water absorption,adhesiveness,bactericidal property and bactericide bactericide rate,timeliness,and impact on concrete fluidity and strength were tested.Then the coated coating and the concrete specimens mixed with fungicide were immersed in artificially strengthened sewage.The macroscopic morphology,surface pH value,mass loss,strength change,microscopic morphology and mineral composition of the corroded specimens were tested and analyzed to explore the anticorrosion mechanism of the composite coating and fungicide.Finally,the key performance indexes of coating and fungicide were evaluated based on grey correlation analysis,and the anti-corrosion measures were further optimized.The results show that the inorganic coating has high water absorption and poor anti-corrosion performance of concrete in the sewage environment.By adding fungicide,it was found that the anticorrosion performance of the inorganic coating was significantly improved,and the mass loss rate of the inorganic coating was 6.4 % after 5 months of immersion in the enhanced wastewater,which was almost close to that of the epoxy coating.The organic coating has low water absorption and good rigid barrier property,especially the oily epoxy glass flake coating has the smallest water absorption,and the bonding strength grade is higher than the waterborne epoxy coating.The anticorrosion performance of the waterborne epoxy coating is slightly lower than that of the oil-based epoxy coating.After the addition of fungicide modification,due to the increase of bactericidal action,the anticorrosion performance of waterborne epoxy coating is better than that of oil-based epoxy coating.After 5 months of corrosion in the enhanced sewage,the quality loss rate of coating waterborne epoxy coating is only 4.3%,the surface is still intact,and the pH value is greater than 10.However,the overall anticorrosion effect of inorganic and organic composite coatings has been improved,and there is not much difference between them and the oily epoxy coatings.According to the schematic diagram and grey correlation analysis,it is concluded that in the early stage of corrosion,the water absorption has a great impact on the corrosion performance of concrete,while in the middle and late stage,the bactericidal property has a significant impact on the corrosion performance of concrete.The test of fungicide shows that the addition of copper phthalocyanine has no adverse effect on the strength and slump of concrete to some extent.After the combination of the selected fungicide,the bactericidal effect of the compound fungicide on microorganisms was significantly improved,especially the copperpentabromo compound fungicide,the bactericidal rate was close to 100%,and there was no adverse effect on concrete.After 60 h,the bactericide rate of compound bactericide can still be as high as 99 %.After soaking in sewage for 4 months,the composite bactericide specimen did not change much from the initial state,while the surface of the single bactericide specimen turned completely black.The surface of zinc oxide and sodium bromide was seriously spalling.The mass loss rate of the composite microbicide specimens is about 3%,while that of the copper phthalocyanine specimens with the best single microbicide effect is 4.52%.Through grey correlation analysis,the main factor affecting concrete's anticorrosion performance is the bactericide rate,followed by the timeliness of bactericide.