EXPLORING THE USAGE OF LITHIUM MINING TAILING CLAY (LMTC) IN CONSTRUCTION MATERIALS

Asphalt binders and Portland cement are the most expensive constituents in paving materials. Efforts to reduce costs while minimizing the carbon footprint have driven research into alternative materials. This preliminary study explores the properties of asphalt binders and Portland cement concrete mixtures modified with varying percentages of lithium mining tailing clay (LMTC), a by-product of lithium extraction. LMTC was also evaluated as a substitute modifier to calcium carbonate (CaCO3) in air-blown binders. To prepare the LMTC-modified binders, a mechanical mixer set at 5000 rpm was used, and the optimal mixing time was determined. Asphalt binders with performance grades (PG) 58-28 and 64-28M were blended with four different percentages of LMTC. Similarly, the air-blown binder was modified with two percentages of LMTC and CaCO3. The rheological properties of the modified binders were analyzed, and the results showed that LMTC and CaCO3 decreased the penetration values and increased the viscosity. Performance tests such as the IDEAL CT and Hamburg Wheel Tracking Tests (HWTT) showed that LMTC enhanced rutting resistance but reduced cracking resistance. Dynamic Shear Rheometer (DSR) testing indicated improvement in the PG, leading to higher resistance to permanent deformation. The use of LMTC in concrete mixtures was also investigated by substituting a portion of cement with LMTC at three different percentages. Tests were conducted to evaluate the concrete slump, compressive, and flexural strength. Results showed that increasing LMTC content decreased compressive strength and slump height. However, the flexural strength for the 5% LMTC concrete mix was comparable to the control mixture and increased slightly at higher LMTC levels. Overall, the findings highlight the potential use of LMTC as an alternative material in asphalt binders and concrete mixtures with promising effects. However, further optimization is needed to balance performance. Once performance enhancements are achieved, it will be essential to quantify the environmental benefits through a comprehensive evaluation, ensuring its contribution to sustainable paving materials

Case Studies for Risk Assessment of Superheavy Load Movements on Flexible Pavements using SuperPACK

This dissertation investigates the evaluation of Superheavy Load (SHL) movements on flexible pavements using the SuperPACK software, an analysis tool developed at the University of Nevada, Reno (UNR). SHL vehicles, characterized by their low travel speeds, extreme gross weights, and unique configurations, pose significant challenges to pavement integrity and safety. This research employs a paper-based format comprising three distinct case studies, each addressing key aspects of SHL impacts: the analysis of unbound layer shear failure under heavy aircraft loading, the identification of critical pavement sections using deflection metrics, and the utilization of traffic speed deflectometer (TSD) measurments for identifying and characterizing critical pavement locations that are most susceptible to failure under the imposed load of an SHL vehicle. These Pilot case studies illustrate the SuperPACK methodology's application while highlighting its computational efficiency and practical value. Through rigorous data analysis and mechanistic modeling, this work contributes to enhancing infrastructure resilience, advancing mechanistic pavement evaluation techniques, and supporting the adoption of risk-based permit processes for SHL vehicle moves

Towards Enhanced Earthquake Resilience: Linking Early Warning Systems, Ground Motion Prediction, and Stress Field Analysis

Earthquakes pose a significant threat to life and infrastructure, making it essential to improve both our understanding and preparedness for seismic events. This study investigates several interconnected aspects of earthquake science to enhance our ability to forecast and mitigate the impacts of these natural disasters. We explore the development of Earthquake Early Warning (EEW) systems, which provide real-time alerts to minimize damage and save lives. While EEW systems like ShakeAlert, the system in operation along the west coast of the US, show great promise, challenges remain, particularly in accurately predicting ground motion and event characteristics in complex tectonic settings. To address this, we examine how fault complexity affects ground motion predictions, emphasizing that realistic fault geometries and fault-zone properties can significantly influence seismic behavior. The study also analyzes the local stress field in tectonically active regions to better understand earthquake dynamics and faulting patterns. Using data from focal mechanism catalogs, we investigate stress orientations and their role in earthquake triggering and fault reactivation. The findings highlight the importance of accurately modeling stress conditions and fault structures to refine seismic hazard assessments. By combining advancements in early warning systems, ground motion prediction, and stress analysis, this research contributes to more effective earthquake preparedness strategies, improving resilience in earthquake-prone regions

Enhancing Virus Reduction in Water Reclamation: Investigation of Long-Term Trends and Treatment Optimization Strategies

Persistent enteric and respiratory viruses, shed into wastewater by symptomatic and asymptomatic individuals, pose significant public health risks if not adequately treated. Existing research often lacks resolution on treatment-level virus removal mechanisms and relies on idealized conditions, limiting its practical applicability. Building on long-term monitoring of SARS-CoV-2 genetic markers in wastewater across the Truckee Meadows region in Nevada, this study aimed to address the critical gaps in demonstrating the predictive power of wastewater concentrations towards public health, investigating the role fate mechanisms have in virus removal and demonstrating the removal efficiency of viral genetic markers in water reclamation. The specific objectives of this work are 1.) identify long-term trends in genetic marker shedding and assess wastewater's potential for predicting disease outbreaks; 2.) quantify the role of factors like adsorption, microbial predation, and endogenous decay in the removal of viral genetic markers in water reclamation processes; and 3.) demonstrate the efficacy of ozonation combined with soil aquifer treatment (SAT) in improving the removal of viral markers before groundwater recharge, especially in water resource-limited communities. The first phase of the work focused on monitoring SARS-CoV-2 genetic markers in untreated wastewater, correlating concentrations with reported clinical case data to identify trends and lead times in disease incidence, with notable peaks aligning with seasonal respiratory virus circulation. Consistent trends were observed, with peaks in disease incidents aligning with seasonal respiratory virus circulation and a 7-day lead-time identified through wastewater surveillance during the early pandemic. However, this was not observed during the circulation of the Delta and post-Omicron variants, possibly due to pandemic management, including vaccinations. Further research quantified viral genetic marker loss through conventional water reclamation processes, revealing negligible removal during primary treatment (p-value: 0.267) and highlighting adsorption during secondary treatment as a critical mechanism, with waste-activated sludge showing a peak concentration of 9.75 log10 GC/day for SARS-CoV-2 genetic markers. Finally, ozonation-SAT enhanced the removal of persistent viral genetic markers and recalcitrant chemical contaminants, including pharmaceuticals. For example, ozonation resulted in a >4-log reduction in norovirus genetic markers and a 2.35 ± 0.4 log reduction for PMMoV, with no significant difference observed between ozonated and non-ozonated SAT processes in PMMoV removal (p-value > 0.999). The ozonation-SAT system also significantly improved the removal of pharmaceuticals such as Sulfamethoxazole (95 ± 0.1%), Meprobamate (73 ± 0.1%), and Primidone (83 ± 0.1%), outperforming conventional SAT processes. These findings highlight the potential for integrating ozonation into existing treatment infrastructure to improve virus and contaminant removal for water reuse applications through SAT and groundwater recharge, particularly in communities with limited resources

Bad Excuses or Difficult Life Situations? A Mixed Methods Analysis of Interactions Within a Mental Health Court

This study examines interactions within one mental health court (MHC) in the western region of the United States in order to determine if there is differential treatment of the MHC’s male and female participants by the courtroom workgroup (CRWG), and what variables, if any, play into that treatment. The sample (n= 49) consists of two groups: males (34) and females (15) observed through court hearings online for a fifteen-month period. These interactions have been measured through attitude, appearance, compliance, status of incarceration, program phase, social service involvement, criminal record, familial relationships, substances, and employment and an Observed Interaction Measure (OIM) for each measure for each group has been calculated. The OIM consists of the measure of participants who experience any interaction with the CRWG regarding the various measures on a 1 (positive interaction), 0 (neutral interaction), or -1 (negative interaction) scale for each time interaction occurs where the lower the score, the more negative the interactions are with the CRWG. The OIM for each measure for males, females, and the sample as a whole in combination with qualitative examinations utilizing an attribution theory and focal concerns theory context informs the results of the study. In general, the results suggest the presence of differences in such treatment for male and female participants. The possible policy and future research implications of the study are also discussed

The Impact of Graded Practicum Course Lesson Enactments on Preservice Teachers’ Self-Efficacy Ratings and Performance Rubric Scores

This quantitative observational study explored changes in preservice teachers’ self-efficacy ratings and performance rubric scores during a single-semester practicum course. The participants, 29 preservice teachers, spent one full day each week in an elementary classroom observing and practicing various aspects of teaching. Central to the course were two graded practice teaching opportunities referred to as lesson enactments. The Teacher Sense of Efficacy Scale (TSES) was administered prior to the first lesson enactment series and after completion of final enactments to measure changes in teacher self-efficacy. All lesson enactments were scored using a course performance rubric. This study aimed to explore the impacts of practicum-based lesson enactments on preservice teachers’ self-efficacy ratings and rubric scores. Paired t-tests were used to analyze changes in teacher self-efficacy ratings and changes in rubric scores. Associations between TSES ratings and rubric scores were explored through comparisons of final TSES ratings and performance rubric scores using Pearson’s r calculations and Spearman’s rank calculations. The results indicated significant increases in both self-efficacy ratings and performance rubric scores, demonstrating the value of incorporating graded lesson enactments in practicum courses. The results of correlations between TSES ratings and rubric scores provided an initial examination of associations between the two instruments exposed areas where future research would benefit educator preparation efforts. These findings have implications for enhancing practicum course designs to better support preservice teacher preparation. Recommendations for future research include further exploration of factors that influence self-efficacy ratings and development, feedback methods, and how these preparation elements can be most effectively combined to optimize lesson enactment opportunities during practicum courses