Effect of Silica Fume on Moisture Flow and the Advective-Dispersive Transport of Ionic Species in Unsaturated Concrete
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Under unsaturated conditions, both moisture flow and the transport of ions strongly depend on the degree of saturation in concrete. In the current literature, most theories and empirical models describe moisture flow and the transport of ions in concrete based on the assumption that concrete is fully submerged in a liquid phase. This simplistic assumption often leads to a systematic underestimation in the amount of ions, such as chlorides, especially in the case of concrete applications subjected to cyclic wetting and drying conditions. In this study, an experimental program was established to determine the key hydraulic parameters needed for modeling the moisture flow and the transport of ions in five types of concrete mixes under unsaturated conditions. The required hydraulic parameters of the five concrete mixes include the saturated hydraulic permeability, the moisture retention function, and the dependency of the relative diffusion coefficient on degree of saturation. A centrifuge technique was used to determine the saturated hydraulic permeability of the five concrete mixes. The moisture retention data of all concrete mixes were determined using a vapour equilibrium technique. The moisture retention data were then used to determine the van Genuchten empirical parameters for an analytical characterization of the capillary pressure-degree of water saturation and the relative permeability-degree of saturation relationships. The dependency of the relative diffusion coefficient on the degree of water saturation was characterized for each type of concrete mix indirectly using an electrical resistivity technique. The experimental results of this study were used in different empirical models that have been originally developed for soils to examine whether they could be applied for concrete The five concrete mixes used in this study were characterized by the usage of a different proportion of dry densified silica fume in each concrete mix. Those mixes were used to determine the effect of silica fume on the experimental and the empirical key hydraulic parameters considered in this study.
DegreeMaster of Science (M.Sc.)
DepartmentCivil and Geological Engineering
CommitteeWegner, Leon D.; Oguocha, Ikechukwuka N.
Copyright DateApril 2013