While cement-mortar lining is widely practiced and has been successful in protecting against electrochemical corrosive effects, recent research indicates that the lining itself may not be immune to corrosion. "Corrosion," in this sense, means the leaching of lime from the mortar, causing calcium loss and possibly leading to structural deterioration of the lining. In addition, leached lime may impair water quality by increasing the pH, alkalinity, and calcium concentrations. The purpose of this project was to study the causes and effects of cement-mortar lining corrosion. Principal objectives were to: investigate the extent of the corrosion problem in the United States; identify factors leading to corrosion; examine the effects of various water quality parameters and cement compositions on cement-mortar corrosion; and recommend measures a utility can implement to minimize corrosion problems. The report focuses on in situ (in place) pipe lining, because only a few problems have been noticed with standard seal-coated and factory-lined pipe. However, factory-lined and seal-coated pipe are also discussed. This paper describes the project. It presents background on cement-mortar lining corrosion, then describes a survey of US utilities to learn about industry experience with lining corrosion. The paper discusses field tests to investigate the causes and control of lining corrosion, and follows with an examination of results in terms of water quality effects and lining effects. It closes with conclusions and recommendations.
