Moisture Diffusivity of Fiber Reinforced Silica Fume Mortars

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Title: Moisture Diffusivity of Fiber Reinforced Silica Fume Mortars

Author(s): E. Denarie and Y. F. Houst

Publication: Special Publication

Volume: 153

Issue:

Appears on pages(s): 763-778

Keywords: diffusivity; drying; moisture content; mortars (material); polypropylene fibers; repairs; silica fume; Materials Research

Date: 6/1/1995

Abstract:
The moisture diffusivity is of considerable importance for quantitative assessments of creep and shrinkage, as well as durability of cementitious material. For this reason, the influence of the composition of repair mortars on their effective moisture diffusivity as a function of the relative humidity of the surrounding air was investigated. Silica fume, superplasticizer, and polypropylene fibers were added to reduce permeability and to control cracking induced by drying shrinkage. It was shown that the moisture transport in cementitious materials can be realistically described by a nonlinear diffusion process governed by Fick's law. A computer program based on the finite volume method was used to get the best effective moisture diffusivity by comparing experimental results (moisture losses of drying mortar cylinders) with the numerical solution. The applicability of a combined experimental-numerical approach to characterize repair mortars regarding their moisture diffusivity was demonstrated. The material properties necessary for the characterization and qualification of new materials can be found numerically. Moreover, the diffusivities obtained provide useful input data for further numerical calculations. The positive effect of the addition of silica fume on moisture diffusivity was clearly shown. The positive combined effect of polypropylene fibers and silica fume with increasing entrained air content was observed. Finally, no significant detrimental effect on the addition of fibers (even at relatively high volumes) has been observed for materials cast under shrinkage free conditions.