1,720,959 research outputs found
Full-Depth Reclamation (FDR) for Suburban/Urban and Local Roads Application
No full textFull-depth reclamation (FDR) as a rehabilitation method improves the service life of pavement structures by reusing asphalt materials, thereby reducing costs and allowing for conservation of nonrenewable resources. However, the lack of mechanicsbased material testing procedures and performance-based specifications limit the use of FDR processes. First, the FDR design and construction process are presented, then, a literature review focusing on FDR research is completed, and a survey is conducted to obtain relevant information regarding current FDR practices in Minnesota. Next, Indirect Tensile Test (IDT) and Dynamic Modulus Test in IDT mode testing is performed on four FDR materials: Field mixed, Lab compacted; Lab mixed, Lab compacted; FDR with cement additive; and FDR with graphene nanoplatelet (GNP) additive. Two curing times are used to determine how physical properties change over time. Test results are used to perform simulations in MnPAVE software and a Life Cycle Cost Analysis (LCCA). Laboratory observations indicate that cement additive reduces predicted life and increases critical cracking temperature with a slight increase in cost; GNP additive reduces predicted life but also reduces critical cracking temperature with a significant cost increase; Lab mixed samples performed better than Field mixed, suggesting that field methods could be improved; and curing has a positive effect on the FDR materials with cement and GNP additives--for both materials, the dynamic modulus increase, and the GNP samples also had a slight increase in tensile strength. MnPAVE simulations and LCCA results indicate that over a 35-year period, FDR may be a more cost-effective method than traditional mill and overlay.Hartman, Marcella; Turos, Mugur; Ghosh, Debaroti; Marasteanu, Mihai. (2016). Full-Depth Reclamation (FDR) for Suburban/Urban and Local Roads Application. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/185541
Investigation of Cracking Resistance of Asphalt Mixtures and Binders
No full textIn this study, the viability of using three test methods for asphalt mixtures and one test method for asphalt
binders are investigated. These test methods are: Bending Beam Rheometer (BBR) for creep and strength of
asphalt mixtures; low temperature Semi Circular Bend (SCB) test for fracture energy of asphalt mixtures; Dynamic
Modulus (E*) test of asphalt mixtures using the Indirect Tensile Test (IDT) configuration; and BBR strength test of
asphalt binders. The materials used in the experimental work were used in MnROAD cells constructed in the
summer of 2016 as part of the MnROAD Cracking Group (CG) experiment, a 3-year pooled-fund project.
The results show that the testing methods investigated provide repeatable results that follow trends similar to
the one observed using traditional methods. The results also show that the properties are highly temperature
dependent and the ranking observed at one temperature can change at a different temperature. In addition, it is
observed that materials with similar rheological properties, such as complex modulus absolute value |E*|, creep
stiffness S, and m-value, do not necessarily have the same fracture resistance. These results confirm one more
time the need for a fracture/strength test for correctly evaluating cracking resistance of asphalt materials.Marasteanu, Mihai; Turos, Mugurel; Ghosh, Debaroti; Matias de Oliveira, Jhenyffer Lorrany; Yan, Tianhao. (2019). Investigation of Cracking Resistance of Asphalt Mixtures and Binders. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/202653
Experimental Investigation of Bio-sealants Used for Pavement Preservation and Development of a New Strength Test for Asphalt Binders at Low Temperature
Get PDFUniversity of Minnesota Ph.D. dissertation. October 2017. Major: Civil Engineering. Advisor: Mihai Marasteanu. 1 computer file (PDF); xii, 139 pages.Surface treatment using sealants as a mean of pavement preservation is an important tool for cost-effectively extending service life of pavement. Sealants have become an important tool for cost-effectively extending the service life pavements. Due to the combined negative effects of asphalt aging and thermal cracking, it is always more challenging to choose an appropriate preservation technique for pavements built in cold-regions. Asphalt aging and thermal cracking negatively affect pavements built in cold climates. Therefore, it is important to evaluate the effects of sealants in laboratory conditions before application in the field to ensure effective performance. However, preservation activities cannot effectively address major distresses, such as low-temperature cracking, that can occur when the pavement was built from the very beginning with less durable materials. Therefore, an essential requirement to mitigate low-temperature cracking of pavements for asphalt materials used in the construction of pavement built in cold- regions is ensuring proper fracture properties of the asphalt materials used in construction. This study has two parts. In the first part, a laboratory evaluation of the effects of adding bio-sealants to both asphalt binder and mixture is performed. The goal is to obtain relevant properties of treated asphalt materials to understand the mechanism by which sealants improve pavement performance. For asphalt binders, a dynamic shear rheometer and a bending beam rheometer were used to obtain rheological properties of treated and untreated asphalt binders. For asphalt mixtures, field cores from both untreated and treated sections were collected and thin beam specimens were prepared from the cores to compare the creep and strength properties of the field-treated and laboratory-treated mixture. It is observed that the oil-based sealants have a significant softening effect on the control binder compared to the water-based sealant and traditional emulsion. Oil-based sealants increased rutting and fatigue potential of the binder and helped the low-temperature cracking resistance. For asphalt mixtures, different trends are observed for the field samples compared to the laboratory prepared samples. Similar to binder results, significant differences are observed between the asphalt mixtures treated with oil-based and water-based sealants, respectively. Additional analyses were performed to better understand the sealant effects. Fourier transform infrared spectroscopy (FTIR) analysis showed that the sealant products could not be detected in mixture samples collected from the surface of the treated section. Semi-empirical Hirsch model was able to predict asphalt mixture creep stiffness from binder stiffness. The results of a distress survey of the test sections correlated well with the laboratory findings. In the second part, a news binder strength testing method is proposed with the goal to provide an effective tool for selecting asphalt binders that are crack resistant. A modified Bending Beam Rheometer (BBR) is used to perform three-point bending strength tests, at constant loading rate, on asphalt binder beams at low temperature. Based on the results, a protocol for selecting the most crack resistant material from binders with similar rheological properties is proposed.Ghosh, Debaroti. (2017). Experimental Investigation of Bio-sealants Used for Pavement Preservation and Development of a New Strength Test for Asphalt Binders at Low Temperature. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/192677
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Formulation of Equivalent Steel Section for Partially Encased Composite Column under Concentric Gravity Loading
Get PDFPartially encased composite column (PEC) consists of thin walled welded H- shaped steel section with transverse links provided at regular intervals between the flanges to inhibit the occurrence of local buckling in the thin flange plates. The space between the flanges and the web plate are filled up with concrete. Extensive experimental investigations have been conducted by several research groups to understand the behavior of this relatively new composite column under both concentric and eccentric loading conditions along with sophisticated non-linear finite element analysis. But the separation between concrete and steel initiates the unstable condition in the finite element analysis near the ultimate point when flange plate buckles. To avoid the expensive and cumbersome modeling of the behavior at the interface of two dissimilar materials, an attempt has been made in this study to replace the composite section of PEC column with an equivalent steel section which can easily be incorporated in commercially available finite element softwares
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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