Evaluation on steel corrosion risk of seawater sea sand concrete with low water-to-binder ratio by electrochemical measurement

The primary challenge in utilizing cement concrete mixed with seawater and/or sea sand lies in the risk of steel corrosion. In this study, the Cl-/OH- ratio of pore solution of seawater sea sand concrete (SSSC) with low water-to-binder (w/b) ratio is evaluated by water extraction technique. Half-cell potential (Ecorr) and corrosion current density (Icorr) serve as parameters for characterizing the electrochemical properties and corrosion risk of steel rebars embedded in SSSC with w/b ratios of 0.2 and 0.4. The findings reveal that the steel corrosion resistance of SSSC with a w/b ratio of 0.2 is significantly higher than specimens with w/b ratio 0.4 due to the lower oxygen, moisture contents and denser microstructure. Over a monitoring period up to 3 years, the results of Ecorr and Icorr confirm that the corrosion rate of steel rebars in SSSC with low w/b ratio is notably lower than that in ordinary SSSC. The corrosion of steel rebar in 0.2-C occurs at initial curing ages and then the steel rebar gradually enters into the passivation state, while the corrosion reaction of steel rebar in 0.4-C continuously proceeds during the whole testing period. Notably, the values of Ecorr and Icorr for SSSC with low w/b ratio exhibit an exponential relationship, while they display a rough linear correlation in ordinary SSSC, influenced by the varying corrosion states of the steel rebar. The results in this study can help to form a theory basis for the development of lifetime prediction model of reinforced UHPC.