Assessing the effect of mineral admixtures on the durability of Prestressed Concrete Cylinder Pipe (PCCP) by means of electrochemical impedance spectroscopy

This paper describes an experimental study to improve the durability of prestressed concrete cylinder pipe (PCCP) mortar coatings exposed to chemical attacks. Three mortar coating mixtures: a control, a 10% FA (fly ash), and 10% SF (silica fume) mortars were investigated. The mortar containing 10% SF was designed specifically to meet the requirements of the XA3 exposure class following EN 206-1. The specimens were immersed in a 9.5 wt% NaCl solution and a composite solution of 9.5 wt% NaCl and 34 wt% Na2SO4 to simulate the most aggressive environment found in the right of way of pipelines in Morocco. Electrochemical impedance spectroscopy (EIS) was used to identify the changes in the microstructure of the mortar coatings and the reinforcement bars. Dong's electrochemical equivalent model was implemented and fitted to the experimental results. It was observed that mineral admixtures can considerably improve the durability of the PCCPs. The 10% SF mortar yielded the best result in terms of corrosion performance. Results also indicated that Dong's model is a more efficient model for describing the electrochemical system of mixtures compared to other circuit models. (C) 2020 Elsevier Ltd. All rights reserved.