Moisture Distribution in Partially Enclosed Concrete

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Title: Moisture Distribution in Partially Enclosed Concrete

Author(s): Wilkins Aquino, Neil M. Hawkins, David A. Lange

Publication: Materials Journal

Volume: 101

Issue: 4

Appears on pages(s): 259-265

Keywords: diffusion; drying; relative humidity

Date: 7/1/2004

Abstract:
The most common deterioration problems in reinforced concrete, such as corrosion, alkali-silica reaction, freezing and thawing, aulfate attack, and others, are associated with the presence of elevated moisture contents in the concrete microstructure. An analytical and experimental study on moisture distribution in partially enclosed drying concrete is presented. The nonlinear diffusion theory was used along with relative humidity measurements to study the problem. Circular concrete columns jacketed with different patterns of impermeable bands were analyzed under simulated, fixed environmental conditions. The clear spacing of the bands was found to have negligible influence on the rate of moisture dissipation (that is, drying) from areas covered by the impermeable bands. On the other hand, the width of the bands was found to have a significant effect on the rate of drying from the covered areas. In addition, the effect of the area covered by the impermeable bands decreased with increasing depth from the surface of the concrete. To validate the analytical results, concrete cylinders were cast, cured, enclosed partially or fully with impermeable bands, and then exposed to a fixed relative humidity environment. Moisture distribution within the cylinders over time was measured using a commercial hygrometer and compared to the numerical predictions. The experimental data confirmed the findings from the numerical studies.