Long-term durability of underground reinforced concrete pipes in natural chloride and carbonation environments

Abstract

In this study, concrete cores extracted from different underground reinforced concrete pipelines exposed to chloride and carbonation environments were investigated. The age of the pipelines was ranging from 43 to 70 years. The main purpose of this study was to determine the minimum concrete cover to reinforcement allowing 100 years of service life with respect to the exposure conditions of the pipelines. Chloride content at the steel–concrete interface, the carbonation depth, the reinforcement corrosion and other concrete durability related properties were assessed. The service-life of the pipelines was thoroughly discussed based on both corrosion rates measured and corrosion induced concrete cracking observed. The high humidity in concrete pipes is suspected to greatly delay oxygen renewal at the steel–concrete interface. Concrete cover of 25 mm and 20 mm seem adequate for 100 years of service life in chloride and carbonation environments respectively.