Reliability of the damage rating index to assess the condition of concrete affected by external sulfate attack

Abstract

The damage rating index (DRI) has proven to be a quite reliable microscopic technique enabling the condition assessment of concrete affected by internal swelling reactions. Yet, very little research has been conducted on the use of the DRI to appraise induced deterioration caused by physical salt attack (PSA) and external sulfate attack (ESA). This study aims to assess the condition of concrete subjected to different salt solutions (i.e. sodium sulfate (Na2SO4), sodium chloride (NaCl), seawater and limewater), and exposure conditions (i.e. partially and fully immersed) through the DRI. Concrete specimens displaying two distinct water/cement ratios (i.e. 0.45 and 0.65) were manufactured and exposed to the above salt solutions for 12 months. Then, the samples were removed from the exposure conditions and prepared for microscopic analysis. The DRI was shown to be an effective technique to assess the condition of PSA- and ESA-affected concrete since different degrees of damage and features were captured for the various exposure conditions studied.