Investigations of chloride ions permeability of pavement concrete under coupled effect of fatigue loading and hydrodynamic pressure

Abstract

ABSTRACT To investigate the combined effects of fatigue loading and hydrodynamic pressure on the chloride penetration and damage process of pavement concrete, a series of chloride penetrations tests, mercury intrusion porosimetry (MIP) tests and scanning electron microscopy (SEM) tests were carried out on specimens after experienced different conditions. Three exposure conditions (i.e. (i): fatigue loading, (ii): fatigue loading and hydrodynamic pressure, (iii): fatigue loading, hydrodynamic pressure and salt–freezing-thawing) were set, and two stress levels (0.5 and 0.7 f) and two pressure values (0.25 and 0.5 MPa) were applied to the specimens. The variation of pore and crack structures of the concrete under different conditions and loading stages was characterised. The results showed that the stress level had a prominent influence on the chloride ion diffusion coefficient (DRCM) when the number of loading cycles ranged from 30 to 60 thousand times, while hydrodynamic pressure promoted the accumulation of damage and presented a distinct effect on DRCM at the latter loading stage. The total capillary pore volume, threshold pore diameter and fractal dimension showed a close positive correlation with DRCM, suggesting that the diffusivity change of concrete accord well with microstructure evolution during the loading process.