Diffusion of Chloride and Cesium Ions in Portland Cement Pastes and Mortars Containing Blast Furnace Slag and Fly Ash

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Title: Diffusion of Chloride and Cesium Ions in Portland Cement Pastes and Mortars Containing Blast Furnace Slag and Fly Ash

Author(s): D. M. Roy, A. Kumar, and J. P. Rhodes

Publication: Special Publication

Volume: 91

Issue:

Appears on pages(s): 1423-1444

Keywords: blast furnace slag; blended cements; cement pastes; cesium; chlorides; diffusion; fly ash; mortars (material); porosity; sea water; sodium chloride; temperature.

Date: 2/1/1986

Abstract:
Diffusion of sodium chloride, cesium chloride and simulated sea water solutions across and into cement pastes and mortars blended with granulated blast furnace slag has been studied. The temperatures of hydration and diffusion were varied between 23and 6O C. Phase chemistry, depth profiles of chloride, and ion migration measurements across paste membranes were used to follow reaction and diffusion of the salt solutions. It was observed that cement mortars containing the slag showed lower penetration depths of Cl- compared to the control portland cement mortars at normal or moderate temperatures. The diffusion of cesium or chloride ions was retarded significantly through the use of slag blending in pastes. The porosity was lower and pore structure was finer in the case of the blended cement, which is considered to be the primary reason for the beneficial effect on diffusion. Phase chemistry studies of blended slag-cement mortars indicated an absence of detrimental reaction products such as gypsum or brucite after exposure, but the presence of Friedel's salt (tetracalcium aluminate dichloride-lo-hydrate) was detected. Comparisons are also made with blends with fly ash, which also showed relatively favorable effects. The electronegative nature of portland cement was elucidated by Cs+ and Cl- migration in pastes.