Some Moisture Sorption Properties of Silica Fume Mortar

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Title: Some Moisture Sorption Properties of Silica Fume Mortar

Author(s): Elisabeth Atlass

Publication: Special Publication

Volume: 132

Issue:

Appears on pages(s): 903-920

Keywords: drying; moisture content; mortars (material); permeability; porosity; silica fume; sorption; thermal gradient; Materials Research

Date: 5/1/1992

Abstract:
Condensed silica fume (CSF) greatly influences not only the mechanical but also the physical properties of concrete. The most striking effect is the reduced permeability, caused by a change in the pore structure. Another sign of this alteration, though not as evident, is the change in the form of the water vapor isotherm. Preliminary results from an investigation concerning the first desorption isotherms of mortar with CSF-cement ratio varying between 0 and 25 percent and a water-cement ratio varying from 0.3 to 0.6 are presented. The results show that CSF influences the pore size distribution not only in the mesopore range, as shown in earlier studies, but also in the micropore range. The drying courses were also recorded in the project and it is clear that CSF significantly prolongs the time in reaching equilibrium, especially in relative humidities below 80 percent. This indicates that the continuous pore system is much narrower when CSF is incorporated. The question of when the "true" equilibrium is attained is discussed.