Detailed investigation of 38 year old concrete sewerage pipes deteriorated by sulphuric acid attack

In Japan, the sewerage pipes constructed during the high economic growth period (1960s- 1970s) are obviously getting older. The maintenance of huge sewerage infrastructure stocks is becoming important. Especially in some cases, the actual service life is rather shorter than the expected life. Due to such deterioration, serious damages such as water leak and roads sinking are often reported. It is clear that this deterioration is due to sulphuric acid attack generated by microorganism activity in drainage. At present, a lot of inspections of corrosion arc ongoing on sewerage pipes. In this research, 38 year old sewerage pipes deteriorated by sulphuric acid attack were investigated on internal concrete deterioration. From this investigation, it was confirmed that deteriorated area of concrete was also neutralized, and Vickers hardness was lower, total pore volume was larger, and the content of Ca was lower than other part of concrete. However, the area behind neutralized area in concrete was not deteriorated. Therefore, deteriorated area could be recognized from non-deteriorated area at a certain depth. These results can be used for improvement of the maintenance technology on drainage facilities for the future.