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EN 480-14:2006 describes a test method for determining the influence of an admixture on the corrosion behaviour of a steel bar embedded in mortar. It combines the advantages of being an accelerated potentiostatic method with being a cast-in method, closer to the application. In the standard, low carbon mild steel bar is cast in standardised mortar conforming to EN 196-1. The investigated admixture is added either to the mixing water or to the sand and the specimen is thereafter cast and a potential is applied. If the admixture is detrimental the current density is expected to increase compared to a reference specimen without admixture. In the adapted method, a stainless steel rebar is cast in the standardised mortar with chlorides, regarded as the detrimental admixture, added to the mixing water. A chloride level of 4% was used and corrosion was considered to have occurred if the current exceeded 0.025 mA/cm2 for a time period of at least 2 hours. This paper includes results for EN 1.4311, EN 1.4436, EN 1.4162 and EN 1.4362, along with the necessary adaption needed in order to use the method to determine the critical chloride threshold level (CCTL). All of the tested stainless steel rebar designations (304LN, 316, LDX 2101, 2304) have passed the cast-in solution test at room temperature and 4% chlorides by cement mass. This indicates that at 90% probability, the 4% chlorides is at least a lower bound for the critical chloride threshold level of tested stainless steel grades. The stainless steel rebar of grade 2304 also passed the CIST at elevated temperature of 40 °C and 4% chlorides. There are indications that the CCTL obtained in the cast-in test are conservative values, due to a high overpotential and a higher chloride concentration in pore solution of the mortar relative to the total chloride content. Further testing with the CIST and the on-going field exposure testing of concrete blocks will provide useful insights concerning the role of concrete matrix on the corrosion resistance of stainless steel reinforcements.
Adaption of EN 480-14:2006 as a test method for determining a critical chloride threshold level for stainless steel rebar
Weitere Titelangaben:
Anwendung von EN 480-14:2006 als Prüfmethode zur Ermittlung des kritischen Schwellenwerts der Chloridkonzentration für Betonstähle aus nichtrostenden Stählen