Effects of further chloride penetration on corrosion resistance of stainless steel bars in RC specimens made with chloride-contaminated raw materials

摘要

In chloride bearing environment, stainless steel reinforcement is one of the options to guarantee the durability of a reinforced concrete structure. Moreover, this kind of bars, characterized by a higher corrosion resistance in comparison to carbon steel bars, could also be considered in case of use of chloride-contaminated raw materials were used for concrete production, allowing overcoming the constraints imposed nowadays by the standard. This would lead to an improvement of the sustainability of the construction industry, allowing the use of seawater or other chloride-contaminated raw materials. Within the SEACON-INFRAVATION project, experimental tests were carried out to investigate the corrosion behaviour of several grades of stainless steel rebars, both austenitic, i.e. 304L and XM-28, and duplex, i.e. 22-05 and 23-04, and for comparison of carbon steel bars, embedded in concretes made with chloride-contaminated raw materials and exposed to the further chlorides penetration. Initially reinforced concrete specimens were exposed to ponding with a sodium solution and corrosion did not occur on any of the stainless steel bars even if a chloride content of about 3.5-4.5% by mass of cement was reached at the bars depth. Later on specimens were subjected to wet and dry cycles with a 3.5% sodium chloride solution. Results showed that after few wet and dry cycles corrosion initiated on XM-28 bars embedded in the concretes made with seawater and chloride-contaminated recycled aggregates.