The main objective of this research was to model the airflow paths through grain bulks and predict the resistance to airflow. The discrete element method (DEM) was used to simulate the pore structures of grain bulks. A commercial software package PFC3D (Particle Flow Code in Three Dimension) was used to develop the DEM model. In the model, soybeans kernels were considered as spherical particles. Based on simulated positions (coordinates) and radii of individual particles, the characteristics of airflow paths (path width, tortuosity, turning angles, etc.) in the vertical and horizontal directions of the grain bed were calculated and compared. The discrete element method was also used to simulate particle packing in porous beds subjected to vertical vibration. Based on the simulated spatial arrangement of particles, the effect of vibration on critical pore structure parameters (porosity, tortuosity, pore throat width) was quantified. A pore-scale flow branching model was developed to predict the resistance to airflow through the grain bulks. Delaunay tessellation was also used to develop a pore network model to predict airflow resistance. Experiments were conducted to measure the resistance to airflow to validate the models. It was found that the discrete element models developed using PFC3D was capable of predicting the pore structures of grain bulks, which provided a base for geometrically constructing airflow paths through the pore space between particles. The tortuosity for the widest and narrowest airflow paths predicted based on the discrete element model was in good agreement with the experimental data reported in the literature. Both pore-scale models (branched path and network) proposed in this study for predicting airflow resistance (pressure drop) through grain bulks appeared promising. The predicted pressure drop by the branched path model was slightly (<12%) lower than the experimental value, but almost identical to that recommended by ASABE Standard. The predicted pressure drop by the network model was also lower than the measured value (2.20 vs. 2.44 Pa), but very close to that recommended by ASABE Standard (2.20 vs. 2.28Pa). / February 2017

Demands for using electrical resistivity techniques (surface and bulk resistivity) as an alternative to the rapid chloride penetrability test (RCPT) have been growing, for example by a number of transportation agencies in North America, to give an indication of the relative penetrability of concrete. While resistivity measurements may reflect the quality of pore structure in the cementitious matrix, their accuracy might be affected by a multitude of parameters including the concentration of ionic species in the pore solution, particularly when supplementary cementitious materials (SCMs) are incorporated in the binder. Hence, a systematic investigation on the resistivity of concrete and its corresponding physical penetrability is warranted. Zinc sacrificial anodes are considered an effective and economical method to prevent the electrochemical corrosion of steel bars by providing cathodic current to bars, which can provide corrosion protection at low galvanic current densities in the range of 0.2 to 2 mA/m2. Sacrificial anodes are commonly used in RC structures particularly in bridge decks to mitigate a critical phenomenon that occurs in the original concrete beside the repaired patches, which is known as the ‘halo effect’. One of the key factors affecting the efficacy of zinc anodes is the resistivity of concrete or cementitious repair material in which these anodes are embedded. There is a general notion that the higher the electrical resistivity of concrete or repair material, the less likely that zinc anodes produce the target galvanic current for optimum protection of steel bars. However, no systematic data are available on the maximum allowable electrical resistivity of repair materials/concretes beyond which zinc anodes cannot properly function to prevent corrosion. In the first part of this thesis, a tripartite relationship (nomogram) to correlate surface resistivity with penetrability (migration coefficient) and porosity of concrete using a wide range ii of concrete mixtures, taking into account the effect of key mixture design parameters (water-to-binder ratio, air-entrainment, SCMs and type of cement) was established. Relationships between surface and bulk resistivity as well as migration coefficient and porosity of concrete were also introduced. In addition, a penetrability classification of concrete based on the corresponding ranges of surface resistivity, migration coefficient and porosity has been proposed. The nomogram and penetrability classification provided reasonable assessment for the condition of field cores extracted from newly constructed and aging concrete pavement. In the second part of this thesis, the functionality of zinc anodes at mitigating patch accelerated corrosion (halo effect) in repaired concrete was explored. Concrete slabs were cast to simulate the patch repair configuration in the field, and the main parameters in this study were changing the resistivity of the repair section in the slabs (5,000, 15,000, 25,000, 50,000 and 100,000 Ω-cm), and anode spacing (25, 100, and 250 mm) inside the repair patch. Analysis of current and potential data shows a high level of effectiveness of the anodes at controlling corrosion in this slab configuration up to 52 weeks under a wetting-drying exposure. / February 2017

Agarose gel was used as a template to prepare zirconium titanium mixed oxide pellets with bimodal porosity. The materials were fully characterized to assess the effect ofZr:Ti ratio on the physical properties. It was found that the metal oxide ratio had an impact on surface acidity, the number of surface hydroxyl groups, the surface area the crystallinity and the mesopore diameter. The oxides were tested for the adsorption of vanadium ions to determine which Zr mole fraction exhibited the highest loading capacity and the fastest kinetics. A comparative study demonstrated that a hierarchical pore structure had enhanced mass transport properties over a monomodal pore structure of similar Zr:Ti composition. / Three porous zirconium titanium oxides (25 mol% Zr) were synthesized using sol-gel chemistry. One of the materials was templated from agarose gel, the second was produced without the use of a template and the third was templated from stearic acid. All three materials varied in pore architecture. Surface modification was performed post-synthetically using propionic acid (a monomer), glutaric acid (a dimer) and three molecular weights of poly(acrylic acid). Higher loading within the inorganic support was obtained for the polymers than for the smaller molecules. It was found that the pore architecture had a strong bearing on the quantity of polymer incorporated into the metal oxide framework and some effect on the rate of polymer adsorption. Thus there is great value in using templates to control pore structure. The materials were subjected to irradiation with 60Co γ-rays to determine the stability of the inorganic support and the organic functionality. / Hybrid materials were prepared by coating five distinct macroporous commercial membranes with zirconium titanium oxide using sol-gel chemistry. Calcination of these templated materials produced oxide membranes which had a suite of macropore and mesopore architectures, pore volumes and surface areas. These differences in physical properties were used to conduct a fundamental study on the relationship between the mesopore size and volume and the capacity for polymer incorporation. It was found that the polymer loading capacity was highly dependent on the pore size and pore volume. As surface area increased, loading capacity decreased, indicating that much of the increased internal surface was inaccessible to the macromolecules. Thus, mesopore diameter and pore volume must be considered when designing a mesoporous solid support. / Hierarchically porous zirconium titanium oxide and carbon zirconium titanium oxide beads with adjustable meso- and macroporosity were prepared in a one-pot, engineering-friendly process. Poly(acrylonitrile) and block copolymer Pluronic F127 were used as structure directing agents. These millimeter sized spheres were fabricated through drop-wise addition of the template-metal alkoxide solution into either water or liquid nitrogen. Carbon zirconium titanium oxide beads were produced by carbonizing the beads at 550 °C in an inert atmosphere. The (carbon) zirconium titanium oxide beads were assessed for surface accessibility and adsorption rate by monitoring the adsorption of uranyl from solution. / Porous metal oxide monoliths, specifically silica, titania, zirconia and mixed oxides containing aluminum and yttrium, were prepared in a one-pot synthesis. Macroporosity was induced using the phase separation of furfuryl alcohol. These materials have a suite of mesopore and macropore structures, the domains of which can be controlled by adjusting the synthesis conditions. These conditions were studied in detail to optimize the pore interconnectivity, the monolith stability, the pore volume and the surface area.