Experimental Study on Pore Formation and Reinforcement Corrosion in Concrete During Freeze - Thaw Cycles

Abstract

Aiming at the problem of the degradation of concrete in freeze - thaw cycles, the pore formation and the consequent reinforcement corrosion in the degradation process were studied. The nuclear magnetic resonance (NMR) technology was proposed to characterize the pore formation of concrete during the freeze - thaw cycle degradation, and the electrochemical workstation was used to study the development of reinforcement corrosion in the reinforced concrete in the process of above-mentioned degradation. Results showed that there were three peaks in T2 (relaxation value) spectrum of concrete during the freeze - thaw cycle degradation. The main peak area representing the micro cracks in the specimen accounted for about 80% of the total area. As the freeze - thaw cycle progressed, the area of the first peak (main peak) in T2 spectrum increased exponentially. Meanwhile, the relation between the corrosion current density and the number of freeze - thaw cycles was exponential, and the relation between corrosion current density and porosity was linear. After 175 cycles, the reinforcements of group A - 2 reached a medium corrosion state, while the specimens of group B - 2 were still in a low corrosion state, indicating that adding fly ash could improve the salt - freezing resistance of the concrete.

Keywords

• concrete|freeze - thaw cycle|nuclear magnetic resonance (nmr)|t2 spectrum|polarization curve