Simulation Study Of The Effect Of Surface Washing On The Corrosion Of Concrete In Sewage Pipes

In recent years,the rapid development of China's economy,the level of municipal infrastructure construction has been significantly improved,sewage discharge is also increasing year by year,resulting in long-term overload operation of sewage pipes,and most of the existing drainage systems in China have been in service for many years and suffered severe corrosion damage.It is imperative to improve the durability of concrete in sewage environment.The corrosion mechanism of the underground sewage pipeline is very complicated,which has the physical effect of the flushing of the sewage water stream,the chemical corrosion of the concrete by the chemical substances in the sewage,and the continuous corrosion of the concrete by the microorganisms in the sewage.In order to simulate the corrosion of concrete in the internal environment of sewage pipeline,this paper firstly designed the water flow flushing device to reduce the flow rate of 0.5m/s,1.0m/s and 1.5m/s in two different corrosive media: sewage/acid solution.The concrete is subjected to the scouring experiment.The soil/acid solution environment is comprehensively evaluated by comparing the trends of macroscopic and microscopic data such as different corrosive media,concrete with different flow rates,compressive strength,corrosion depth,surface pH,mineral composition and element distribution.The effect of different flow rates on the corrosion of concrete.And the growth of biofilm under different flow rates of sewage was compared.Secondly,some of the test blocks immersed in the sewage/acid solution environment are periodically washed with a high-pressure water gun,and the macroscopic and microscopic data of the test blocks in different corrosive media environments are recorded and compared,and the presence or absence of the sewage/acid solution environment is compared.The effect of the corrosion layer on the subsequent corrosion of the concrete.Finally,the grey correlation theory is applied to find out the key influencing factors of concrete corrosion in various measurement indexes of corrosion layer in different periods of sewage scouring.The results show that under different flow rate sewage scouring conditions,in the first 1-3 months of the experiment,the regularity is that the flow rate is larger,the mass loss and corrosion depth are more obvious;and the flow rate of 1.5 m/s is reached in 4~6 months.Corrosion is still stabilized at the previous corrosion rate,but the corrosion rate of 0.5m/s and 1.0m/s flow rate is obviously accelerated.At the end of the experiment,the mass loss of 1.0m/s is 5.5%,and the loss is the most serious;The mass loss of /s and 1.5 m/s conditions was 4.0% and 4.4%.Under different flow rate acid solution scouring conditions,the corrosion trend is the greater the flow rate,the more serious the corrosion,and with the increase of experimental time,the corrosion gap between different flow rates becomes more and more obvious.At 6 months,0.5m/ The mass loss of s,1.0m/s and 1.5m/s flow rates were 3.12%,4% and 5.8%,respectively.Experimental results for the corrosion layer: The corrosion rate of the corrosion layer under the sewage condition is substantially constant,and the corrosion rate is faster and faster without flushing the corrosion layer.The corrosion effect of the etched corrosion layer under sulfuric acid conditions is obvious,and the corrosion is slow without rinsing the corrosion layer.Corrosion layer thickness,porosity,surface pH,corrosion layer calcium content and compressive and corrosion resistance coefficient were monitored regularly under different flow conditions.The gray correlation data was analyzed to obtain the correlation between corrosion index and corrosion in different experimental time.The analysis results show that the surface pH is the most relevant to corrosion in the first 3 months before corrosion,and the porosity is the highest correlation with corrosion when the experiment is carried out until 6 months.