Corrosion of steel reinforcement in concrete of different compressive strengths

摘要

Corrosion of steel bars embedded in concrete having compressive strengths of 20, 30 and 46 MPa was investigated. Reinforced concrete specimens were immersed in a 3% NaCl solution by weight for 1, 7 and 15 days. In order to accelerate the chemical reactions, an external current of 0.4 A was applied using portable power supply. Corrosion rate was measured by retrieving electrochemical information of polarization technique. Pull-out tests of reinforced concrete specimens were then conducted to assess the corroded steel/concrete bond characteristics.Experimental results showed that corrosion rate of steel bars and bond strength between corroded steel/concrete were dependent on concrete strength and accelerated corrosion period. As concrete strength increased from 20 to 46 MPa, corrosion rate of embedded steel decreased. First day of corrosion acceleration caused a slight increase in steel/concrete bond strength, whereas sever corrosion after 7 and 15 days of corrosion acceleration significantly reduced steel/concrete bond strength. Visual and metallo-graphic observation of steel bars removed from concrete samples after testing revealed that the severity of corrosion reactions and reduction of steel bar diameter increased as the corrosion acceleration period increased. Presence of localized corrosion pits as well as severe corrosion grooves of steel bars was confirmed after 7 and 15 days of corrosion acceleration, respectively.