Brett Tempest

Characterization and Demonstration of Reuse Applications of Sewage Sludge Ash

In this paper sewage sludge ash (SSA) refers to ash material product of incineration of municipal and industrial sewage water. SSA from a waste water treatment plant in Eastern United States was characterized in order to investigate and demonstrate potential reuse applications for the ashes produced by this plant. To date most research on reuse applications for ash materials has focused largely on coal-sourced ashes such as fly ash or bottom ash. In contrast very little research has been reported on SSA, which typically will have important differences with coal-based ashes in terms of physical and chemical composition and cementitious properties. This paper presents the results of an elemental and morphological characterization as well as a demonstration of clay brick admixture and soil stabilization admixture reuses applications.

Mitigating Leachability from Fly Ash Based Geopolymer Concrete Using Recycled Concrete Aggregate (RCA)

Geopolymer concrete was synthesized from coal fly ash, which contains the range of silica and alumina that is needed for the formation of geopolymer phase. Studies on the leachability of geopolymer concrete made from fly ash have shown that it leaches out elements such as arsenic (As), chromium (Cr) and selenium (Se), which are of great environmental concern due to their toxicity and high mobility in the alkaline pH range that can be found in pore solution of geopolymer concrete. The leaching of these elements in high pH environment can be reduced by the addition of calcium that aids in the formation of calcium silicate hydrates (CSH) or precipitates of calcium. In this study, recycled concrete aggregate (RCA) was used as the additional calcium source in making geopolymer concretes. Different mixes were produced with 100% natural aggregate (coarse and fine) and by replacing 10% and 50% coarse aggregate with coarse RCA. The Dutch availability test (EA NEN 7371) was utilized in investigating leachability from the geopolymer samples. The results demonstrate that the use of RCA affects the compressive strength and reduces the leachability of oxyanion elements from geopolymer concrete.

Post-Fire Nondestructive Evaluation of a Prestressed Concrete Double-Tee Joist Roof

AbstractPrestressed concrete exhibits resistance to damage induced by fire and associated elevated temperatures, often permitting reuse of structural elements following exposure to accidental fire. However, prudent determination of suitability for reuse or rehabilitation of fire-damaged prestressed concrete requires a post-fire structural evaluation, which can be greatly aided by application of nondestructive testing for quantitative assessment of residual material properties, structural strength, and serviceability. In this study, a suite of nondestructive inspection and evaluation methods including visual documentation, camber surveying, penetration resistance testing, and impact-echo are applied to fire-damaged and unaffected double-tee joists of a precast, prestressed roof system. Qualitative and quantitative measures of fire damage obtained through the nondestructive tests are presented and strong correlations, in particular between longitudinal wave speed estimates obtained in impact-echo testing an...

Tire Derived Aggregates As a Sustainable Recycled Material for Retaining Wall Backfills

Tire derived aggregates (TDA) offer potential environmental, technical, and economical benefits for retaining wall applications. For example, when compared to natural soils, TDA materials offer the advantage of reduced lateral pressures and settlement due to smaller unit weight, and potentially higher drainage capacity. This paper presents a technical and economical assessment of TDA materials for retaining wall backfills. The technical assessment includes results on model retaining wall tests and also from centrifuge tests to assess the lateral pressures generated by TDA materials. The lateral pressures are compared to tests using conventional mineral soil backfills. The test results show TDA backfills generate lower lateral pressures for at- rest conditions and for active conditions. The lower lateral pressures, coupled with lower unit weights translate into substantially lower retaining wall costs due to savings from smaller wall and footing dimensions, and less steel reinforcement quantities associated with the lower loading demand.

Leaching Characteristics of Geopolymer Cement Concrete Containing Recycled Concrete Aggregates

AbstractIn this investigation, the effect of replacing some percentage of natural coarse aggregate with recycled concrete aggregate (RCA) in geopolymer concrete synthesis is studied. The study focuses on the compressive strength and release of elements from the geopolymer concrete samples. The toxicity characteristic leaching procedure (TCLP) was used to determine release of potentially hazardous heavy metals (PHHMs) and other constituents of potential concern (COPCs) from the geopolymer concrete and also to identify if the material should be categorized as either hazardous or nonhazardous. It was found that replacing virgin aggregates with RCA had a small impact on the compressive strength of the concrete, reducing it by a maximum of 34%. As measured by toxicity characteristics leaching procedure (TCLP), release of As was reduced by adding RCA. The leached concentrations of the elements, Ba, Cd, Cr, and Pb were found to be below TCLP regulatory limits.

Pre-college interactions, early expectations, and perceived barriers of first year Black and Latino engineering students

One of the most significant challenges facing engineering education in the United States is the persistent problem of inclusion and retention of underrepresented racial and ethnic groups. As part of a larger, federally funded project on student-faculty interaction in engineering, a case study was conducted to describe engineering-related interactions prior to college, perceived barriers during engineering studies, and early expectations of interactions with faculty among first year Black and Latino engineering students at a large university in the Southeastern United States. Descriptive data were gathered through focus groups and questionnaires. Findings indicated that recommendations from pre-college educators, mostly middle and high school math and science teachers, were important for deciding to study engineering in college. Students had expectations of minimal contact with engineering faculty based on early interactions, but expressed the desire to seek relationships with professors who would be able to connect them with engineering-related opportunities and resources. The most likely perceived barriers to studying engineering were financial problems and difficulties in science and engineering coursework. These findings are particularly useful to engineering education professionals involved with first year orientation experiences, and they further current understanding about pre-college and early experiences that are linked to engineering enrollment.

Predicting Corrosion-Related Bridge Durability with Laboratory-Measured Permeability Results

AbstractA variety of complex modeling techniques is available to estimate the onset of chloride-induced corrosion in reinforced concrete infrastructure. Despite great progress in this area during t...

Engineering self-efficacy, interactions with faculty, and other forms of capital for underrepresented engineering students

To address the chronic issues of underrepresentation in engineering education, a small but growing body of research has examined social and cultural explanations for engineering persistence among women, racial/ethnic minorities, first-generation college students, and other underrepresented groups. In this exploratory study, we examine the extent to which relationships with engineering faculty and other forms of engineering-related capital (e.g., aspirational, navigational) are related to engineering self-efficacy among underrepresented engineering students. The findings of the study have implications for future research and practice to increase access to engineering education and persistence of underrepresented students in engineering.

Process and Lessons-Learned From an Interdisciplinary Collaboration in the Design and Construction of a Net-Zero Energy Solar House

This paper reviews the development process of a net-zero-energy modular house, called UrbanEden, which was the UNC-Charlotte entry to the 2013 US Department of Energy Solar Decathlon competition. It reports the collaboration of students and faculty from various colleges and schools at UNC-Charlotte working towards delivering a net-zero energy house for the competition held in October in Irvine California.The study presents the participation of students involved in various phases of schematic design, design development and construction. It also identifies the composition and organization of students through the two-year progress and how it evolved throughout the process. The paper also reviews the curriculum integration in school of Architecture with Engineering. The lessons learned from the process will be discussed.Copyright

BUILDING MATERIALS RECLAMATION PROGRAM

This report describes work conducted on the Building Materials Reclamation Program for the period of September 2008 to August 2010. The goals of the project included selecting materials from the local construction and demolition (CD five materials were selected for more detailed investigations. In the Engineering Feasibility and Dissemination Phase, a conceptual study for a regional (Mecklenburg and surrounding counties) collection and sorting facility was performed, an engineering feasibility project to demonstrate the viability of recycling or reuse schemes was created, the literature review was extended and completed, and pedagogical materials were developed. Over the two-year duration of the project, all of the tasks and subtasks outlined in the original project proposal have been completed. The Final Progress Report, which briefly describes actual project accomplishments versus the tasks/subtasks of the original project proposal, is included in Appendix A of this report. This report describes the scientific/technical aspects (hypotheses, research/testing, and findings) of six subprojects that investigated five common C&D materials. Table 1 summarizes the six subprojects, including the C&D material studied and the graduate student and the faculty advisor on each subproject.