In this work we have reviewed methods to classify corrosivity of ground waters. Weight loss and stress corrosion cracking (SCC) corrosion tests have been done for rebar and steel strand. No clear indication of SCC was found. The application of tensile stress to 85 % of yield strength increased general corrosion rate significantly in very corrosive waters. The effect of corrosion protection on the axial behavior of steel strands was determined by double pipe axial tests with different embedment lengths. The results showed a significant difference on behavior between epoxy-coated steel strands, galvanized steel strands and plain steel strand.

Dans la presente etude, nous avons passe en revue des methodes permettant de classifier la corrosivite des eaux souterraines. Des tests portant sur les pertes de poids et sur la corrosion FCC (la fissuration par corrosion sous contrainte) ont ete effectues pour les barres d'armature et les torons. Aucune indication nette de FCC n'a ete constatee. L'application d'une contrainte de traction allant jusqu'à 85 % de la limite d'elasticite a accru de manière significative la vitesse generale de corrosion dans les eaux très corrosives. L'effet de la protection contre la corrosion sur le comportement axial des torons en acier a ete determine au moyen de tests axiaux à double tube avec des longueurs d'enrobage differentes. Les resultats ont mis en evidence une difference significative quant au comportement entre les torons en acier à revêtement epoxy, les torons en acier galvanises et les torons en acier standard.

In dieser Arbeit haben wir Methoden geprueft, die korrosive Wirkung des Grundwassers einstufen. Gewichtsverlust- und SCC-Korrosionstests wurden fuer Stahlstabe und Drahtlitzen durchgefuehrt. Es wurden keine sicheren Hinweise auf Spannungsrisskorrosionsbrueche gefunden. Bei Anwendung einer Dehnbelastung von 85 % der Streckspannung bzw.Ergebnisstarke stieg die allgemeine Korrosionsrate in stark korrosivem Wasser deutlich an. Die Wirkung des Korrosionschutzes bei axialem Verhalten von Stahldrahtlitzen wurde durch axiale Tests an Doppelleitungen unterschiedlicher Versenkungslange determiniert. Die Ergebnisse zeigten im direkten Vergleich von epoxidbeschichteten, galvanisierten und normalen Stahldrahtlitzen beachtliche Unterschiede im Verhalten auf.

Introduction

Cable bolting has been used successfully in reinforcing the stopes in mines in Finland since 1971. The most used cable bolt material has been seven-wire steel strand. The interest of expanded use of cable bolting also in civil rock engineering has been increasing due to the many benefits of cable bolting method and the material properties of steel strand. However, the uncertainty of the sensitivity to corrosion and mechanical applicability have been the main problem to be solved before cable bolts can be accepted to use in a long-term reinforcement.

"Corrosion protected cable bolts in long-term reinforcement" research projects were carried out in the Helsinki University of Technology in 1999–2002. The object of the projects was to study the applicability of corrosion protected cable bolts in long-term reinforcement. The project was divided into two parts. In the first part the axial load-displacement behavior of test bolts was determined by double pipe pull tests with different test configurations.

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