Abstract:
Pore water is an important agent to passivation and protection of concrete reinforcement. This fluid, present in capillary pores of the hardened cementitious material, has a very high pH due to its composition of alkalis, and is in direct contact with the steel in reinforced and prestressed concrete. The presence of additions in Portland cement, such as pozzolans, fillers and metallurgical slags, may influence the composition of pore water and, consequently, the resistance of reinforcement to corrosion. Higher or lower alkali contents (Na+ and K+) may be present in the fluid, so as Ca2+, resulting from the hydration process of the material. Aggressive ions such as chloride may also be present. In the present work, an electrochemical evaluation of the CA-50 steel corrosion behavior in two pore waters was made, which compositions simulate those extracted by pressure from pure and composite cement pastes, to which chloride ions were added. By means of potentiodynamic polarization and electrochemical impedance spectroscopy, it was found that pore waters promote the passivation of the steel, preventing the development of the corrosion process, and that the presence of the aggressive agent promotes a significant acceleration of the process, as well as the breaking of the passive layer. The results also indicate that, in the presence of chloride, pore water composition is relevant to determine the corrosion mechanism.
Reference:
VIEIRA, Renan Esposito; MENNUCCI, Marina M.; QUARCIONI, Valdecir Angelo; MELO, Hercílio G. de. Estudo da influência da composição da água de poro sobre a corrosão do aço CA-50. In: CONGRESSO INTERNACIONAL DE CORROSÃO, INTERCORR, 2016, Búzios. Proceedings… Rio de Janeiro: ABRACO, 2016. 12 p.
Pore water is an important agent to passivation and protection of concrete reinforcement. This fluid, present in capillary pores of the hardened cementitious material, has a very high pH due to its composition of alkalis, and is in direct contact with the steel in reinforced and prestressed concrete. The presence of additions in Portland cement, such as pozzolans, fillers and metallurgical slags, may influence the composition of pore water and, consequently, the resistance of reinforcement to corrosion. Higher or lower alkali contents (Na+ and K+) may be present in the fluid, so as Ca2+, resulting from the hydration process of the material. Aggressive ions such as chloride may also be present. In the present work, an electrochemical evaluation of the CA-50 steel corrosion behavior in two pore waters was made, which compositions simulate those extracted by pressure from pure and composite cement pastes, to which chloride ions were added. By means of potentiodynamic polarization and electrochemical impedance spectroscopy, it was found that pore waters promote the passivation of the steel, preventing the development of the corrosion process, and that the presence of the aggressive agent promotes a significant acceleration of the process, as well as the breaking of the passive layer. The results also indicate that, in the presence of chloride, pore water composition is relevant to determine the corrosion mechanism.
Reference:
VIEIRA, Renan Esposito; MENNUCCI, Marina M.; QUARCIONI, Valdecir Angelo; MELO, Hercílio G. de. Estudo da influência da composição da água de poro sobre a corrosão do aço CA-50. In: CONGRESSO INTERNACIONAL DE CORROSÃO, INTERCORR, 2016, Búzios. Proceedings… Rio de Janeiro: ABRACO, 2016. 12 p.
