Location

University of Leeds

Keywords

Durability, Chloride diffusion, Water saturation, Pore structure, Cementitious materials

Abstract

Chloride-induced corrosion of reinforcement in concrete structures is a serious issue in engineering practice. This paper investigates the influence of pore structure on the relative chloride diffusion coefficient Drc in unsaturated cementitious materials. The effects of various pore features, including porosity, pore size, and pore connectivity, on the continuity of water-filled pores in unsaturated porous systems are analyzed based on the Kelvin law and water desorption process. In the experimental program, different cementitious materials (OPC, slag, fly ash, and limestone powder) were used to prepare paste and mortar samples. The Drc of the mortar samples (one year old) at various degrees of water saturation was determined based on the Nernst-Einstein equation and conductivity tests. The pore structure of the paste samples (one year old) was measured by the mercury porosimetry technique. It is found that a finer pore size distribution or lower pore connectivity tends to result in a lower Drc. The pore size effect on the Drc is pronounced primarily at high saturation levels. The Drc at low saturation levels is dominated by the pore connectivity effect. The mortars blended with fly ash or slag exhibit lower Drc-value than the OPC mortar of the same saturation level.

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Influence of Pore Structure on Relative Chloride Diffusion Coefficient in Unsaturated Cementitious Materials

University of Leeds

Chloride-induced corrosion of reinforcement in concrete structures is a serious issue in engineering practice. This paper investigates the influence of pore structure on the relative chloride diffusion coefficient Drc in unsaturated cementitious materials. The effects of various pore features, including porosity, pore size, and pore connectivity, on the continuity of water-filled pores in unsaturated porous systems are analyzed based on the Kelvin law and water desorption process. In the experimental program, different cementitious materials (OPC, slag, fly ash, and limestone powder) were used to prepare paste and mortar samples. The Drc of the mortar samples (one year old) at various degrees of water saturation was determined based on the Nernst-Einstein equation and conductivity tests. The pore structure of the paste samples (one year old) was measured by the mercury porosimetry technique. It is found that a finer pore size distribution or lower pore connectivity tends to result in a lower Drc. The pore size effect on the Drc is pronounced primarily at high saturation levels. The Drc at low saturation levels is dominated by the pore connectivity effect. The mortars blended with fly ash or slag exhibit lower Drc-value than the OPC mortar of the same saturation level.