Corrosion behavior of stainless steel in chloride-contaminated carbonated concrete

The use of chloride-contaminated raw materials can minimize the consumption of natural resources, e.g., fresh water and virgin rocks, in the production of concrete to increase the sustainability of the construction sector. However, the possible benefits in terms of improved sustainability of concrete can only be evaluated on the long term, considering the durability (i.e., concrete's ability to guarantee an adequate service life when exposed in operating conditions). In this research, the use of stainless steel reinforcement in combination with chloride-contaminated concrete has been studied to construct durable and sustainable concrete infrastructures. Preliminary results showed that both austenitic (i.e., 304L and XM-28) and duplex (i.e., 23-04 and 22-05) stainless steels are suitable to be used in concrete made with chloride-contaminated raw materials and exposed to different environmental conditions, without chloride penetration. However, when stainless steel bars are embedded in carbonated concrete, their corrosion resistance might be impaired. This article compares the corrosion behavior of the different stainless steels, two austenitic (304L and XM-28) and two duplex (23-04 and 22-05), embedded in alkaline and carbonated concrete and exposed to different controlled environmental conditions to simulate aggressive environments. Results showed that 304L, 23-04, and 22-05 stainless steels are suitable to be used also in concrete contaminated by chlorides even after carbonation and in the harshest exposure conditions. Conversely, corrosion might initiate on XM-28 when exposed to the most aggressive exposure conditions.