Matching Items (4)
Filtering by
- Genre: Masters Thesis
Description
Heating of asphalt during production and construction causes the volatilization and oxidation of binders used in mixes. Volatilization and oxidation causes degradation of asphalt pavements by increasing the stiffness of the binders, increasing susceptibility to cracking and negatively affecting the functional and structural performance of the pavements. Degradation of asphalt binders by volatilization and oxidation due to high production temperature occur during early stages of pavement life and are known as Short Term Aging (STA). Elevated temperatures and increased exposure time to elevated temperatures causes increased STA of asphalt. The objective of this research was to investigate how elevated mixing temperatures and exposure time to elevated temperatures affect aging and stiffening of binders, thus influencing properties of the asphalt mixtures. The study was conducted in two stages. The first stage evaluated STA effect of asphalt binders. It involved aging two Performance Graded (PG) virgin asphalt binders, PG 76-16 and PG 64-22 at two different temperatures and durations, then measuring their viscosities. The second stage involved evaluating the effects of elevated STA temperature and time on properties of the asphalt mixtures. It involved STA of asphalt mixtures produced in the laboratory with the PG 64-22 binder at mixing temperatures elevated 25OF above standard practice; STA times at 2 and 4 hours longer than standard practices, and then compacted in a gyratory compactor. Dynamic modulus (E*) and Indirect Tensile Strength (IDT) were measured for the aged mixtures for each temperature and duration to determine the effect of different aging times and temperatures on the stiffness and fatigue properties of the aged asphalt mixtures. The binder test results showed that in all cases, there was increased viscosity. The results showed the highest increase in viscosity resulted from increased aging time. The results also indicated that PG 64-22 was more susceptible to elevated STA temperature and extended time than the PG 76-16 binders. The asphalt mixture test results confirmed the expected outcome that increasing the STA and mixing temperature by 25oF alters the stiffness of mixtures. Significant change in the dynamic modulus mostly occurred at four hour increase in STA time regardless of temperature.
ContributorsLolly, Rubben (Author) / Kaloush, Kamil (Thesis advisor) / Bearup, Wylie (Committee member) / Zapata, Claudia (Committee member) / Mamlouk, Michael (Committee member) / Arizona State University (Publisher)
Created2013
Description
Over the last two decades, Alternative Project Delivery Methods (APDM), such as Design-Build (DB), have become more popular in the construction industry, specifically in the U.S., and the competition for APDM projects has risen among construction companies. The Engineering News Record (ENR) magazine analyzes DB firms and publishes the list of the top 100 every year. According to ENR articles and many scientific papers, the implementation of DB method has grown drastically over the last decade, however, information about growth trends depending on firm size and segment is lacking. Also missing is knowledge the future market trends over the next five years. Furthermore, public agencies and DB firms may be worried that DB projects do not distribute wealth equally among DB firms. Using the top 100 firms deemed representative of the DB market, the author has divided the market into volumes based on rankings to analyze the total DB market revenue growth. A comparison between international and domestic revenues indicated that the top five DB firms have 64% more involvement in the international market compared to the domestic market. Furthermore, while the research shows increasing market share only for the top five firms, the author has found that (1) a large portion of their market share is due to a large growth in their international market, and (2) revenues for all volumes of the DB market have increased. Moreover, regression and time series analyses allow for the forecasting of the DB market growth, which the author anticipate to move from about $100B to about $150B in 2020.
ContributorsVashani, Hossein (Author) / El Asmar, Mounir (Thesis advisor) / Ernzen, James (Committee member) / Bearup, Wylie (Committee member) / Arizona State University (Publisher)
Created2014
Description
This research explores some of the issues, challenges and dilemmas of existing research found in the construction workforce, it starts with past research that can be found on the current problems in the industry and how it has developed. It covers the distinguishing factors that influence a construction company's success and how it has affected depending on the characteristics of the company. It was to examine the effectiveness of the recruitment and selection practices of entrants in the construction industry workforce and pathways to improve those practices.
ContributorsHatfield, Whitney (Author) / Ariaratnam, Samuel (Thesis advisor) / Chasey, Allan (Committee member) / Bearup, Wylie (Committee member) / Arizona State University (Publisher)
Created2017
Description
The water and wastewater industry in the United States is in dire need of renovation due to dwindling infrastructure and requires substantial reinvestment. Design-bid-build (DBB) is the traditional method of project delivery most widely applied in this industry. However, alternative project delivery methods (APDM) are on the rise and touting the benefits of reduced project schedule and cost. The main purpose of this study is to conduct a qualitative and quantitative performance evaluation to assess the current impact of APDM in the water and wastewater industry. A national survey was conducted targeting completed water and wastewater treatment plant projects. Responses were obtained from 75 utilities and constructors that either completed their projects using DBB, construction manager at risk (CMAR), or design-build (DB). Data analysis revealed that CMAR and DB statistically outperformed DBB in terms of project speed and intensity. Performance metrics such as cost growth, schedule growth, unit cost, factors influencing project delivery method selection, scope changes, warranty and latent defects, and several others are also evaluated. The main contribution of this study was that it was able to show that for the same project cost, water and wastewater treatment plants could be delivered under a faster schedule and with higher quality through the utilization of APDM.
ContributorsFeghaly, Jeffrey (Author) / El Asmar, Mounir (Thesis advisor) / Ariaratnam, Samuel (Thesis advisor) / Bearup, Wylie (Committee member) / Arizona State University (Publisher)
Created2018