Electrochemical repair techniques in carbonated concrete. Part I: electrochemical realkalisation

Abstract

Corrosion induced by concrete carbonation can be controlled through the application of electrochemical techniques such as cathodic protection (CP) or electrochemical realkalisation (ER). These methods are generally considered effective in the repair of structures; however, few data are available on the effects of different parameters such as the concrete composition or the exposure conditions. For the temporary technique of ER, moreover, scarce information exists on the durability of the treatment. An experimental research was carried out, aimed at investigating some aspects connected with the application of these techniques in reinforced carbonated concrete. Six different types of concrete mixes were considered. The tests were performed both in a wet and a dry environment. The effect of the pre-corrosion of the reinforcement in concrete was also considered. This article presents results obtained with the technique of ER and discusses the role of the different factors considered. The technique of CP will be discussed in Part II.

Durabilidad del hormigón armado expuesto a condiciones agresivas

“…Otro factor importante es la relación agua/cemento, se reporta que a mayores relaciones el espesor del hormigón realcalinizado es superior (155,158); a su vez en presencia de relaciones agua/cemento reducidas es necesario mayor densidad de corriente y tiempo de tratamiento (155). Respecto al efecto de diferentes electrolitos, tales como, hidróxido de calcio, hidróxido de potasio, carbonato de sodio, carbonato de potasio, se reportan como de mayor eficacia en la RE el carbonato de sodio y el hidróxido de potasio (159).…”

“…De los estudios realizados en el tema se puede inferir que el método de realcalinización puede resolver el problema de carbonatación en hormigón armado, extendiendo la vida útil (142,(155)(156)(157)(158)(159)(160)(161)(162), sin embargo, se sugiere utilizar esta técnica como un método preventivo, es decir, antes que la corrosión haya alcanzado a la armadura (159,163), ya que no está claro que se genere una repasivación de las barras de acero (161).…”

“…Another important factor is the water/cement ratio: the higher the ratio, the deeper the realkalinisation depth (155,158), while concrete with lower water/ cement ratios call for higher current densities and treatment times (155). Sodium carbonate and potassium hydroxide have been identified as the most effective ER electrolytes (159).…”

“…The studies conducted on the subject indicate that realkalinisation can solve the carbonation problem in reinforced concrete, extending its service life (142,(155)(156)(157)(158)(159)(160)(161)(162), although this technique is suggested for use as a preventive method only, i.e., before corrosion affects the reinforcement (159,163), for it has not been shown to repassivate steel rebar (161).…”

Durability aspects of electrochemical realkalisation treatment

“…Literature contributions on the short-term effects of ER are relatively numerous, for instance in terms of the role of several parameters (as concrete composition and circulated charge) on concrete realkalisation and on corrosion conditions of steel reinforcement (Mietz 1995, Redaelli & Bertolini 2011, Tong et al 2012, Yeih & Chang 2005. Conversely, contributions regarding the long-term effects are few.…”