Analysis of a Corrosion Failure of Prestressed Concrete Cylinder Pipe: A Pilot Study

This paper presents the findings of a pilot study designed to better understand the underlying causes of the high failure rates of the Prestressed Concrete Cylinder Pipe (PCCP) used in the semi-arid regions of Morocco. The study used mini-pipes (made of mortar coating and reinforcing steel) immersed in basins to simulate their performance in a near real-life service environment. Four basins were evaluated: Basin 1 (control basin) contained the control soil, whereas the other three basins contained chemically enriched soils (Basin 2 with sulfate solution; Basin 3 with chloride solution; and Basin 4 with combined chloride-sulfate solution). Each basin had four mini-pipes made from OPC mortars and a PCC mortar with 17% fly ash. In this paper, electrochemical impedance spectroscopy (EIS) technique was used to assess the corrosion process of the reinforcing steels specimen while a scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX) was used to study the steel-mortar interface. The preliminary results revealed, as expected, that the mini-pipes in Basin 4 had the highest corrosion rates. It was also found that the PCC mortar with 17% fly ash produced the best corrosion performance results in all four basins, implying that if used, can significantly improve the service life of pipes in semi-arid regions.