ASSESSMENT, SELECTION, AND SPECIFICATION OF CATHODIC PROTECTION MEASURES IN REINFORCED CONCRETE INFRASTRUCTURES AND HISTORIC BUILDINGS

摘要

A proven methodology for providing assessment, selection and specification of cathodic protection measures in reinforced concrete infrastructures and historic buildings is described. An on-site condition evaluation survey is first required. Evaluation and survey will consist of implementation of several analysis techniques including visual examination to detect defects, petrography to determine concrete condition, and various electrochemical measurements such as half cell potential mapping, linear polarization, continuity, stray current identification and resistivity. Laboratory analysis of petrographic and corrosion product samples should be conducted by an experienced petrographic specialist. Petrographic evaluation will determine aggregate type and size, depth of carbonation, air void content and mode of deterioration if present. These will determine integrity of concrete and the best means of rehabilitation and corrosion protection. Based on the above work, determination of extent of damage and remaining service life are made. Critical questions to be answered are is the reinforced concrete infrastructure sound, and does it require repair or replacement? Consideration is given to materials selection for repair and/or replacement of the structural components. In addition to concrete repair materials, this may include alternative corrosion-resistant materials. Preliminary design and specification is subsequently undertaken of a suitable repair system, and of a cathodic protection system. Cathodic protection (CP) is a method wherein a sufficient amount of electric or impressed current (DC) is continuously supplied to a submerged or buried metallic structure to mitigate, slow down or stop altogether the natural corrosion processes from occurring. A galvanic anode cathodic protection system generates DC as a result of the natural electrical potential difference (electrochemical reaction) between the metal to be protected (cathode) and another metal to be sacrificed (anode). Case studies applying this methodology to reinforced concrete infrastructures and historic buildings are provided.