Macro and micro aspects of the transport of chlorides in cementitious membranes

Abstract

A study of the transport of chlorides through hardened Portland cement paste membranes is reported. The flux of chlorides was induced by migration (AC and DC fields) and diffusion.Two parallel studies were developed. A macroscopic one where the migration of chlorides was followed by Electrochemical Impedance Spectroscopy (EIS) and a microscopic one in which the natural diffusion was investigated using the scanning electrochemical microscopy (SECM). Both studies have revealed to be complementary. The local investigations performed with the SECM were successfully employed for the interpretation of the EIS data.The results have shown that the transport of chlorides occurs mainly through pores of submicrometre equivalent diameter. The study of the transition time has allowed to conclude that the diffusion coefficient approaches the usual value obtained in bulk solution. The macroscopic study has allowed presenting an explanation for the beneficial effect of the AC current in the transport of chlorides. A possible method for estimating the flux of chlorides from the percolation resistance is also discussed.

Influence of the properties of granite and sandstone in the desalination process by electrokinetic technique

“…Therefore as the ionic content is being reduced, the resistance increases and the electrical current that flows through the sample, when a constant voltage is applied, should decrease as indicated in [9,23,24,26].…”

Evaluation of electrode-sample contact impedance under different curing humidity conditions during measurement of AC impedance of cement-based materials

“…Many researchers [43][44][45][46] simulated the electric field distribution in cement sample. B. Díaz et al 43 simulated the influence of cell geometry on the measurement of resistivity of the cement-based materials, and found that the effect of the electric field distribution is a function of the resistivity.…”

The roles carbonate and bicarbonate ions play on pre‐passive HRB400 rebars in simulated pore solutions of deteriorating concrete

“…Previous studies have defined the concept of critical chloride threshold, beyond which steel rebars will be depassivated . In addition, the transport mechanism of chloride ions through cement‐based materials has been fully studied . Therefore, it is possible to predict the initial time for the depassivation of steel rebars caused only by chloride ingress …”