Effect of oxygen permeability on corrosion properties in mortar specimens mixed with bacillus subtilis

Ehime University, Civil and Environmental Engineering, 3, Bunkyocho, Matsuyama, Ehime, Japan

^* Corresponding author: kkawaai@cee.ehime-u.ac.jp

Abstract

The effect of the degree of water saturation on oxygen permeability in mortar specimens mixed with an aerobic microorganism of bacillus subtilis (natto) under various water saturation conditions is explored in this study. In the experimental program an immersion test was conducted using distilled water and salt water (10%) under room conditions controlled at a constant temperature of 20°C. The oxygen permeability on the surface of steel bars embedded at different saturation conditions in mortar specimens were examined by electrochemical measurements e.g. half-cell potential measurements, cathodic polarization techniques. Based on the results obtained, the rate of oxygen permeability of the mortar specimens mixed with the bacillus subtilis (natto) was clearly reduced from the age of 28 days to 91 days. The humid environment is advantageous to the metabolic activity of bacillus subtilis (natto) which is likely to occur in saturated conditions compared to those in relatively dry environments. This led to more negative half-cell potentials in the mortar specimens mixed with the bacillus subtilis (natto) especially under the saturated conditions. The variations of half-cell potentials could be attributed to variations of cathodic polarization properties which is illustrated by decreased oxygen permeability in the specimens.