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Full-Text Articles in Engineering

Testing And Modeling Of The Thixotropic Behavior Of Cementitious Materials., Bashir Hasanzadeh Dec 2017

Testing And Modeling Of The Thixotropic Behavior Of Cementitious Materials., Bashir Hasanzadeh

Electronic Theses and Dissertations

During construction, concrete goes under various operations. It is normally transported to the job site, be placed and consolidated in the formwork, etc. The easiness and quality of these operations are very much related to the intrinsic rheological properties of concrete. Therefore, a good understanding of rheological behavior of concrete under various conditions are needed. Thixotropy is an important part of rheology. The thixotropic behaviors of concrete can be good representatives of its flow behaviors on the job site. For example, the breakdown aspect of thixotropy can help to explain how its flow behavior can impact concrete pumping and its …


Engineering Applications Of Organic Surfactant Modified Bentonite In Sorptive Soil Barriers., Sadra Javadi Aug 2017

Engineering Applications Of Organic Surfactant Modified Bentonite In Sorptive Soil Barriers., Sadra Javadi

Electronic Theses and Dissertations

Earthen barriers such as CCLs and GCLs have been employed in geotechnical practices to provide a low permeability hydraulic barrier since long time ago. These types of barriers exhibited satisfactory performance for many applications such as landfills. The performance of low permeability barriers is based on the swelling potential of their component, which is mostly Na-bentonite, in contact with polar fluids such as water. However, the acceptable range of conductivity cannot be achieved by traditional earthen barriers when they are permeated by non-polar fluids such as gasoline. This phenomenon occurs due to the incompatibility of earthen barrier constituent with non-polar …


Cationic Surfactant Modification And Its Impact On The Engineering Behaviors Of Montmorillonite., Mohammad Ghavami Aug 2017

Cationic Surfactant Modification And Its Impact On The Engineering Behaviors Of Montmorillonite., Mohammad Ghavami

Electronic Theses and Dissertations

This study focuses on the microstructure of organoclays after organic surfactant modifications and the potential use in geoenvironmental engineering applications including waste containment in earthen barrier, rheological control agents for drilling fluid and soil stabilization. Organoclays, or clays modified by organic matters, are often synthesized by exchanging the naturally occurring interlayer inorganic cations (e.g., Na+, Ca2+) of the clay with organic cationic surfactants. In this research, montmorillonites intercalated with two quaternary ammonium surfactants, hexadecyltrimethylammonium (HDTMA+) and bis (hydrogenated tallow alkyl) dimethyl ammonium were used as the representative organo-rich, partitioning clays. The laboratory characterization techniques including XRD, TEM and …


A Smart Highway Work Zone Merge System Enabled By Connected Vehicles., Abdulmaged Algomaiah Aug 2017

A Smart Highway Work Zone Merge System Enabled By Connected Vehicles., Abdulmaged Algomaiah

Electronic Theses and Dissertations

Typical traffic control and operations at work zones usually are not very effective in mitigating the work zone bottleneck. A major reason is that the common early merge behaviors limits utilizing the available capacity in the closed lane, especially under moderate to high traffic demands. Recently, using late merge strategy is encouraged to prevent early merge behavior and fully utilize the closed lane and therefore increase capacity of work zone. The development of late merge strategy was not enough to substantially improve the situation due to the lack of compliance and communication among drivers. This thesis suggests and investigates a …


The Macro-Modelling Of Steel Fiber Reinforced Concrete/Mortar Flexural Tensile Behavior And Mix Optimization For Flexural Strength., Li Liu Aug 2017

The Macro-Modelling Of Steel Fiber Reinforced Concrete/Mortar Flexural Tensile Behavior And Mix Optimization For Flexural Strength., Li Liu

Electronic Theses and Dissertations

With the continuous advances in materials’ technology, the performance of the commonly used concrete building material has continued to improve. Compressive strengths exceeding 75 MPa are now being used in applications throughout the world. However, the concrete becomes less ductile and more susceptible to sudden failures with increases in its compressive strength. Although the behavior of concrete is generally governed by its compressive strength, its tensile strength, although much lower, is also important. This tensile strength impacts appearance, the serviceability and durability of concrete elements. In addition, minimum levels of tensile strength are required for many concrete applications including, earthquake …


Effect Of High Cationic Flocculant On Anaerobic Digestion Of Municipal Wastewater., Prathap D. John May 2017

Effect Of High Cationic Flocculant On Anaerobic Digestion Of Municipal Wastewater., Prathap D. John

Electronic Theses and Dissertations

Anaerobic digestion (AD) of municipal sludge is a widely used stabilization process at municipal wastewater treatment plants. It is highly effective in reducing sludge volume and produces methane gas which is used as fuel in the wastewater plant. Following digestion sludge is sent to a centrifuge to separate the solids from the liquids. Louisville MSD adds flocculent to material in the centrifuge to better coagulate the solids, thereby aiding in separation of the solids from the liquids. The potential for further AD, COD reduction, and methane generation of the liquid effluent from the centrifuge was unknown, particularly in regards to …


Non-Contact Based Structural Damage Assessment Using Stochastic Subspace Identification And Finite Element Model Updating., Li Yang May 2017

Non-Contact Based Structural Damage Assessment Using Stochastic Subspace Identification And Finite Element Model Updating., Li Yang

Electronic Theses and Dissertations

This research proposed and verified an innovative method to identify and locate structural damage using only the response of operational vibration, that is the displacement acquired by a non-contact optical method. The most efficient and economical way to detect damage within the structure is to monitor its structural health while in operation. However, the uncertainties and the randomness of ambient vibrations due to the operation and environments cause a challenge in conducting the operational analysis. Current technology limits the ability to collect data on the properties of the structure without the interruption of operation. Frequencies and mode shapes have been …


A Tool To Evaluate Sustainability Of Pavement Maintenance Projects., Yibo Zhang May 2017

A Tool To Evaluate Sustainability Of Pavement Maintenance Projects., Yibo Zhang

Electronic Theses and Dissertations

Pavement maintenance activities are widely regarded to be critical elements during pavement life cycle, different maintenance techniques have been used to restore or extend the service lives of pavements. However, the existing maintenance practices on pavement system have problems that impair the economic benefits, disturb the natural environment, and somewhat ignore the needs from stakeholders. To minimize these negative impacts, sustainability is an ideal way because it addresses the problems under Triple Bottom Line (TBL, refers to economy, environment, and society). Sustainability analysis within transportation or pavement industry has been studied in different countries, but the concept of sustainable pavement …