Katherine Kuder

Rheology of Extruded Cement-Based Materials

Current research efforts seek to develop extruded high-performance fiber-reinforced cement-based composites (HPFRCC) for use in residential housing applications. Part of this effort focuses on reducing the high material cost that is associated with extrusion processing by replacing costly cellulose ethers with less expensive clay binders. The minimum amount of two different types of cellulose ethers that was needed to achieve extrudability was determined and then the possibility of reducing the ethers with two clay binders was explored. The results show that cellulose ether content can be reduced by using alternate clay binders. In addition, two different extrusion-based rheological characterization methods were used to describe the fresh state properties of the extruded materials: the Benbow-Bridgwater model and capillary rheology. Capillary rheology was shown to be effective at describing extrudability, providing an indication of the fresh state parameters necessary for extrusion.

Tailoring Extruded HPFRCC to be Nailable

Extruded high-performance fiber-reinforced cementitious composites (HPFRCC) have a number of attributes that make them attractive materials to be used in residential applications, including superior mechanical performance and durability. The constructibility of these materials, however, can be improved, particularly the ability of the material to be nailed. In this work, the material parameters that govern nailing are sought so that nailable extruded composites can be produced. Nailing performance is experimentally evaluated using a test method developed previously. Existing fracture mechanics-based and cavity expansion-based models are used to understand the role of the fiber reinforcement and the matrix in the penetration process. Based on the findings from these models, nailable lightweight composites are produced. The results indicate that by properly tailoring both the matrix and the fiber reinforcement, nailable composites can be achieved. Nailable composites are shown to have a high fracture toughness (to control cracking) and a matrix with a low density and compressive strength (for ease of nailing).

High-Early-Strength, High-Resistivity Concrete for Direct-Current Light Rail

AbstractStray current from direct-current light rail systems can corrode underground metal pipes, potentially causing significant damage to utility lines. To address this problem, Seattle Public Ut...

CAPILLARY RHEOLOGY OF EXTRUDED CEMENT-BASED MATERIALS

Extrusion processing is a technique used to produce high-performance fiber-reinforced cement-based composites (HPFRCC), which has shown great promise for manufacturing materials that are strong, ductile, durable, design versatile and environmentally friendly. Despite these advantages, extrusion is still primarily limited to laboratory-scale work. One reason this technology has not been adopted by industry is the high cost of the cellulose ether processing aids that are required for extrusion. In this research, the possibility of partially replacing cellulose ethers with less expensive clay binders is investigated. Extrudable and not extrudable mixes are identified and capillary rheology is used to describe the rheological parameters of the various mixes. The results indicate that clay binders can be used as a partial replacement for cellulose ethers and that capillary rheology can be used to describe extrudability. Extrusion, capillary rheology, processing, clay, cellulose ether

Rheology of fiber-reinforced cement systems using a custom built rheometer

Fiber reinforcement can be used to enhance the mechanical performance and durability of cement-based materials. However, incorporation of fibers can have an adverse effect on the fresh state properties of these materials. To use fiber reinforcement effectively, the effect that fibers have on the rheology of cement-based composites must be understood. In this work, a custom designed and built parallel plate rheometer is used to evaluate the fresh state properties of stiff cementitious systems. Previous work showed that this rheometer produces reasonable results and that the parameters obtained with the rheometer compare well with other established values. In this work, the rheometer is used to study a variety of stiff cementitious systems. The effect of water and sand content on the rheology of cement paste is determined. Finally, the fresh state characteristics of stiff steel fiber-reinforced cement paste is evaluated and conclusions are drawn about the influences of the reinforcement on flow behavior.