The Effect of Calcium Leaching on the Chloride Diffusivity of Hydrated Tricalcium Silicate Pastes

Abstract

Calcium leaching of cement-based materials induces detrimental effects on diffusion properties related to long-term durability. This paper investigates the effect of calcium leaching on the chloride diffusivity of hydrated tricalcium silicate (C3S) pastes. Different concentrations of ammonium nitrate solutions were used to accelerate the calcium leaching of C3S pastes. The degree of alternation of C3S pastes was characterized by Ca/Si. The chloride diffusivity of the leached C3S pastes was obtained by the steady-state electro-migration test. Results show that the chloride diffusivity of the leached C3S pastes increases with the increasing degree of alteration. Compared with the sound C3S pastes, the diffusivity of the leached C3S pastes is increased 1.8-3.6 times depending on the degree of alteration.

Influence of Micro-Pore Connectivity and Micro-Fractures on Calcium Leaching of Cement Pastes—A Coupled Simulation Approach

“…The increases in porosity and coarser microstructure would result in an increase in transport properties. With the tricalcium silicate pastes leached in ammonium nitrate solution, the chloride diffusivity of leached pastes could increase by a factor of 1.8 to 3.6 depending on the alteration level [25]. On the other hand, the dissolved gas diffusivity of leached cement (CEM I) paste samples might increase more than one order of magnitude depending on the defusing gases and initial microstructure of the materials, as shown in the study of Phung et al [26].…”