Research On The Corrosion And Prevention Of The Concrete In Urban Sewage

Under the environment of urban sewage, a large amount of concrete structures processing or conveying sewage was given a severe corrosion, which makes the service life of concrete can not meet the expectations of use fixed number of year, and the most serious is microbial corrosion. In the study of microbial corrosion of concrete prevention measures, the modification of concrete and the use of surface coating are relatively passive measures, that can not suppress the generation of microorganism, so adding bactericide in the concrete is a more active measure that used in the concrete corrosion protection. In this test, using the anaerobic sludge in the second pond to prepare for the artificial strengthening sewage, simulating the microorganisms on the accelerated corrosion of concrete; designing and processing the corrosion of concrete test device in the sewage; contrasting on different sewage and water immersion environment, the specimens mixed with different kinds of fungicides, immersed in wastewater in different positions respectively, and the research of different types of corrosion mechanism.Different with the law of concrete specimen soaking in water, under the sewage water environment, the flexural strength of concrete before 28 d is raising, the growth rate can reach 7.1%. Along with the age growth, the strength of the concrete continue to fall more than 28 d, the 150 d drop rate can reach 12.4%.And in this environment, concrete flexural strength of the specimens are more clearly than compressive strength degradation, flexural strength can characterize the degradation performance laws of the samples. Similar to the intensity of law, the quality of concrete specimen under water immersion is falling, the mass loss rate can reach 2.24 ‰ and 2.24 ‰ in 28 d and 150 d; the quality of the specimen soaking in water showed a trend of rising, especially the first 8 weeks the rising trend are obvious, and the gradually rising to 150 d is leveling off. It illustrate that soaking specimens in the sewage had been eroded. Comparing with the pulp, mortar, concrete specimen soak or partial immersion in the sewage, we can find that the concrete partial immersion in the sewage is better than all the concrete performance of the immersion in the wastewater; The corrosion resistance of the specimens of different aggregate sequence is: the net pulp > mortar > concrete. On the one hand is due to the part of the soaking specimens in the sewage the contact area is smaller than all soaked in water, on the other hand is due to aggregate into interface, making the corrosion resistance of materials.The effect is not too ideal after mixed with dodecyl dimethyl benzyl ammonium chloride in the concrete specimens, the corrosion effect is even less wastewater, so it is not suitable for used as fungicide in concrete. The intensity attenuation coefficient and quality loss rate of the specimens mixed fungicide are reduced, showing that mixed bactericide can reduce the corrosion effect of sewage, the strength of specimen mixing fungicide can improve 17.2%,the corrosion effect of sewage have improved after mixing sodium bromide in concrete specimens and it is the best anti-corrosion property; Mixing sodium tungstate in concrete specimens also has prevention function, but the effect is worse than sodium bromide, only reach 80% quality of it; and the volume expansion rate is 84.6%.In the micro test, by comparing the pore structure, XRD, and the images of electron microscopy scanning found that mixing fungicide and soak in water environment all CH content decreases; Porosity and large pore volume increased, structure of sewage water mudstone porosity is about 1.5 times than the clean water porosity; Cement structure become loose and there are some ettringite produced, mixing with fungicide can bring obvious inhibiting corrosion effect.