1,720,958 research outputs found
Integrating UAV-Based LiDAR and Imaging Data for Semi-Automated Detection of Water Ponding in Pavement Networks
Full text linkThis study leverages Unmanned Aerial Vehicles (UAV) by collecting LiDAR data and RGB imagery to detect pavement surface irregularities prone to water ponding. Such areas can impose safety risks to road users, especially under severe weather conditions. The collected data was georeferenced and imported to an ArcGIS platform to enable surface hydrological simulation. The feasibility of the proposed approach is evaluated through three case studies in an urban setting. Superimposing the surface characteristics obtained from the UAV with the hydrological models could allow for semi-automated identification of the hotspots of hydroplaning as well as accelerated moisture damage in a timely manner, which would be otherwise impractical to detect through manual inspections. Use of UAV for large-scale data collection proved to be cost-effective and timely. This approach offers a scalable solution for urban planners and infrastructure managers aiming to enhance transportation safety.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Optimizing the Performance of Asphalt Mixes with High Reclaimed Asphalt Pavement Content Using Rejuvenators
Full text linkReusing reclaimed asphalt pavement (a.k.a., RAP) has become a routine in the production of asphalt paving materials. Theoretically, RAP is a hundred percent recyclable material since its main components are high-quality, graded aggregates coated with durable asphalt binder. Unfortunately, due to the presence of the aged asphalt binder, most agencies only approve a limited percentage of RAP, either less than 20% to 30% of RAP (by weight of the total mix) or less than 25% of RAP binder replacement (by weight of the total binder content), to be incorporated in new asphalt mixes. For decades, pavement researchers have shown great enthusiasm for promoting the RAP rate in asphalt mixes. One of the most promising approaches is to use rejuvenators to restore the aged asphalt binder to a comparable or even better performance than the virgin asphalt binder. However, there is still a lack of knowledge and practice in using rejuvenators in producing sustainable and durable recycled asphalt mixes. The gap is not only limited to the type of rejuvenators to be used, but also to the optimal dosage, compatibility with virgin and RAP binder, stability under the elevated temperature atmosphere, mix design and manufacturing process, and uncertainties about the long-term performance of the revitalized high RAP mixes. As a result, this research was initiated to investigate the use of rejuvenators for optimizing the performance of asphalt mixes with higher RAP content.
This study used seven commercial rejuvenators provided by various suppliers, as well as materials collected at local asphalt plants and refineries for the experimental work, which included six bio-based oils, one petroleum-based oil, one processed RAP, graded virgin aggregates, and two virgin asphalt binders. A sequential screening methodology was applied to evaluate the rejuvenating efficacy of these rejuvenators and a soft binder using various binder and mix tests and data analysis tools. In the first part of this research, rejuvenated binder blends with different RAP binder ratios (25%, 50%, and 75%) and rejuvenator dosages (0%, 5%, and 10%) were prepared to select candidate rejuvenators with better restoration capacities in terms of reducing the viscosities at mixing and compaction temperatures as well as recovering the continuous performance grade (PG) temperatures, non-recoverable compliance, and crossover temperature measured binder testing using the Dynamic Shear Rheometer (DSR) and the Bending Beam Rheometer (BBR). Four bio-based rejuvenators were selected in the first stage and used for dosage optimization through the blending chart method and the response surface modelling (RSM) method. The blending chart method assumes a linear relationship between the rheological index and two variables, rejuvenator dosage and RAP binder ratio. Therefore, the optimal rejuvenator dosage can be determined when the rejuvenated binder blend resembles the same rheological index as a target virgin binder. Meanwhile, the response surface model was built based on a two-level factorial design, which involved the different rheological indices as the responses and the rejuvenator dosage and RAP binder ratio as the two factors. This method can verify the linear relationship and then the model can be used to calculate the optimal dosages. From the results, the blending chart method was proved to be reliable because most of the rheological indices were expected to have a linear relationship with the rejuvenator dosage and the RAP binder ratio. Furthermore, the recommended indices, the low PG temperature based on m-value (PGLm) and the crossover temperature (Tcross), exhibited the potential to ensure that the rejuvenated binder blends have adequate cacking resistance without compromising the permeant deformation resistance at high temperatures.
In the mix testing phase, the Hamburg Wheel-Tracking (HWT) test results revealed concerns about increased permanent deformation and moisture susceptibility due to the additions of rejuvenators in high RAP mixes at both test temperatures, 44°C and 50°C. However, the rejuvenated high RAP mixes outperformed the control mix (with 20% RAP), particularly at the higher test temperature. The cracking test results obtained from the Indirect Tensile Asphalt Cracking Test (IDEAL-CT) indicated that the addition of rejuvenators or replacing the base binder with a softer virgin binder was beneficial in improving the cracking resistance; however, more testing results, preferably from plant trial mixes, are needed for statistical analyses. Nonetheless, the rejuvenated high RAP mixes achieved decent high-temperature stability and acceptable cracking resistance, especially after an extended oven conditioning period. The dynamic modulus test was used to investigate the effect of increased RAP content with the use of a rejuvenator (or a soft binder) on mix rheology at a variety of temperature and loading frequency combinations. The measured modulus and phase angle data were analyzed using two master curve models and several time-temperature-dependent shifting equations. Additionally, the long-term performance of the asphalt mixes was assessed by comparing test results obtained from samples before and after the long-term oven aging (LTOA) protocol. The high RAP asphalt mix with the addition of a rejuvenator showed the most stiffness increase after long-term aging; however, it retained relatively better flexibility and temperature sensitivity compared to other mixes.
According to the findings of this study, using rejuvenators in asphalt mixes with a high RAP content can produce a recycled HMA with balanced rutting and cracking performance and long-term sustainability. Whereas in the high pavement in-serve temperature range, extra care should be taken for moisture susceptibility
Development and Evaluation of Testing Protocols for Fatigue Damage and Crack-Healing of Bituminous Mixtures
No full textFatigue testing is a very important performance test for asphalt concrete mixtures and has been studied for many years with varying levels of success. However, there are several imperfections in the commonly used fatigue tests. Furthermore, there is currently no universal standard to define fatigue failure in these tests, as fatigue damage cannot be effectively quantified due to the presence of bias effects. Researchers have used modified fatigue tests to study the self-healing capability of bituminous material. The healing capability of the material is typically quantified by comparing the modulus change with and without rest periods. However, the presence of reversible phenomena makes it even harder to quantify the healing effects. This research aims to improve the laboratory asphalt concrete fatigue damage and crack-healing tests by combining Non-destructive testing (NDT) methods.
This study was conducted on polymer-modified asphalt concretes. The properties of the material used has been well studied in previous research and were used to compare with the results from this research. An ultrasonic pulse propagation test (UPPT) was conducted on undamaged specimens, specimens under monotonic loading and cyclic loading conditions, and during the healing processes. Two experimental protocols that combine traditional asphalt fatigue or cracking tests with UPPT to quantify and evaluate the damage and self-healing property of asphalt concrete were proposed. Several signal processing techniques were applied to study the performance of the test material.
The results indicate that the UPPT method is sensitive to the microstructure, viscosity, elasticity, damage level and healing properties of asphalt concrete. The proposed Dynamic High-frequency Healing with Rest Period (D2HRP) test protocol successfully distinguishes changes in healing between stiffer and more aged binders. The combination of ultrasonic pulse propagation tests and tension-compression tests provides an indirect observation of changes of material property during the test, and the proportion of the bias effects were successfully quantified. The improved laboratory cracking and fatigue tests can promote sustainability in pavement materials and designs. Furthermore, this project will also contribute to a better understanding of crack initiation and propagation processes in pavement materials, which can improve the existing state of pavement rehabilitation and maintenance techniques as well as pavement condition prediction models
Chemo-rheological Characterization of Asphalt Binders Using Different Aging Processes
No full textThe performance and longevity of asphalt pavements depend heavily on the properties of asphalt binders, which are affected by aging, binder modifications, and the incorporation of reclaimed asphalt pavement (RAP) materials. However, significant gaps exist in understanding the long-term chemical and rheological changes induced by aging processes (particularly with respect to differences between thermo-oxidative aging and UV exposure), and in the use/standardization of chemical analytical techniques such as Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy for binder characterization. Furthermore, the behaviour in RAP-virgin binder blends, along with the influence of bio-based rejuvenators and anti-aging additives under different aging conditions, remains underexplored. Addressing these gaps are crucial to developing more durable, sustainable pavements. This thesis bridges these research gaps through comprehensive investigation of chemo-rheological binder characterization, combining experimental testing with advanced analytical tools and varying aging methods. The findings offer essential insights into binder aging, rejuvenation strategies, and modification techniques, with significant implications for pavement durability and environmental sustainability.
The first chapter presents an evaluation of Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy combined with functional group and multivariate analysis techniques to characterize asphalt binders. The research identifies challenges in repeatability across binder sources and aging states demonstrating the importance of standardized protocols for improving reliability. Repeatability as described by AASHTO standards is listed in the precision and bias statement as single operator precision. This is the allowable difference in two test results measured under the repeatability conditions (same asphalt binder, measured by the same operator, on the same piece of equipment in the same lab). Principal Component Analysis (PCA) and k-means clustering successfully classified binder types and aging states, with large quantity (LQ) sample preparation yielding more consistent results than small quantity (SQ) preparation. These findings underscore the need for uniform procedures in binder analysis, addressing inconsistencies prevalent in the current literature.
The second part of the thesis investigates the impact of Styrene-Butadiene-Styrene (SBS) polymer modification on binder performance and oxidative resistance. Using Nuclear Magnetic Resonance (NMR) and ATR-FTIR spectroscopy, along with PCA and Partial Least Squares Regression (PLSR), the research highlights the ability of SBS to enhance high-temperature performance and slow thermo-oxidative aging. This work not only confirms previous findings on SBS but also provides new insights into the molecular interactions contributing to aging resistance. The study fills a gap in understanding how SBS-modified binders behave under various aging scenarios, offering a deeper perspective on polymer-modified asphalt technologies.
The thesis also addresses a critical gap related to UV-induced aging, which has been underexplored in comparison to thermo-oxidative aging. A novel UV aging chamber was developed to simulate real-world environmental conditions, incorporating UV exposure, water spray cycles, and controlled heating at 70°C. Comparative analysis revealed that different additives exhibit varying effectiveness under UV and thermo-oxidative conditions. Zinc diethyldithiocarbamate (ZDC) showed strong resistance to thermo-oxidative aging but limited efficacy under UV aging, while ascorbic acid (Vit. C) accelerated aging under UV exposure, contrary to expectations. These findings emphasize the challenges involved in designing effective anti-aging strategies for asphalt binders, demonstrating the value of combining conventional rheological tests with spectroscopic techniques and further highlighting the need for more targeted approaches to additive selection and development.
This thesis advances the understanding of asphalt binder behaviour and aging processes by integrating chemical, rheological, and multivariate analysis techniques. It offers critical contributions to the standardization of binder characterization protocols, the optimization of polymer-modified asphalt technologies, and the development of more effective anti-aging strategies. The research also demonstrates the potential of machine learning and artificial intelligence (AI) in predicting binder performance from spectroscopic data using multivariate analysis, paving the way for future innovations in asphalt binder characterization.
In conclusion, the work in this thesis addresses significant gaps in the literature, providing new insights into aging mechanisms, additive/rejuvenation strategies, and RAP binder interactions. By combining chemical analysis, rheological testing, and multivariate techniques, this research contributes both to academic knowledge and practical pavement engineering, promoting the development of more sustainable, long-lasting asphalt pavements
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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