Verification and Improvement of the Rate of Asphalt Aging Simulated by AASHTO PP1–98 Protocol

2005 ◽  
Vol 1901 (1) ◽  
pp. 24-32
Author(s):  
Suresh Raghavendra ◽  
Claudia E. Zapata ◽  
M. Waseem Mirza ◽  
William N. Houston ◽  
Matthew W. Witczak
Keyword(s):  
The United States ◽  
Age Hardening ◽  
Asphalt Binders ◽  
Pavement Performance ◽  
Ongoing Research ◽  
Aging Conditions ◽  
Original Laboratory ◽  
Laboratory Procedures ◽  
Pavement Aging

It is well documented that environmental effects play a significant role in characterizing material properties, which in turn affect pavement performance. Studies under the Strategic Highway Research Program (SHRP) were carried out on the age-hardening characteristics of asphalt binders and mixes. As a result, laboratory procedures to simulate the field hardening of asphalt binders and mixes, AASHTO Provisional Protocols PP1–98 and PP2–99, were developed. The approaches followed in these procedures are of great value for the ongoing research on pavement aging; however, due to limited resources and time constraints under the SHRP program, these provisional procedures have certain limitations. A research study, NCHRP Project 9–23, was initiated to overcome these limitations and enhance the predictive capabilities of these protocols. The current research paper is a part of NCHRP 9–23, which deals with the PP1–98 protocol. Binders and field cores were obtained from long-term pavement performance and other sites across the United States. Original, laboratory-aged, and field-aged binders were characterized through dynamic shear rheometer testing. The existing protocol was verified; on the basis of the findings, the protocol was improved to include the effect of field aging conditions and mix properties. The developed model was calibrated and validated with field data. Parametric analysis was performed on the final model to ascertain the practicality of the output. On the basis of those findings, a recommended provisional protocol was developed. The recommendations apply only for conventional, nonmodified binders.

Evaluation of Age-Hardening on Long-Term Aged Asphalt Binders

2021 ◽  
Vol 304 ◽  
pp. 124687
Author(s):  
Yanlong Liang ◽  
John T. Harvey ◽  
David Jones ◽  
Rongzong Wu
Keyword(s):  
Age Hardening ◽  
Asphalt Binders ◽  
Aged Asphalt

Effect of Hydrated Lime on Long-Term Oxidative Aging Characteristics of Asphalt

2002 ◽  
Vol 1810 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Shin-Che Huang ◽  
J. Claine Petersen ◽  
Raymond Robertson ◽  
Jan F. Branthaver
Keyword(s):  
Phase Angle ◽  
Fatigue Cracking ◽  
Hydrated Lime ◽  
Age Hardening ◽  
Asphalt Binders ◽  
Asphalt Pavements ◽  
Initial Stiffness ◽  
Oxidative Aging ◽  
Useful Lifetime

An experiment involving neat asphalts AAD-1, ABD, and their mixtures with two different grades of hydrated lime was conducted to investigate the effect of lime on the long-term aging characteristics of asphalt binders. Rheological properties of unaged and aged asphalt-lime mixtures were measured with a dynamic shear rheometer at 25°C (77°F) and 60°C (140°F). The addition of hydrated lime to one asphalt (AAD-1) effectively reduced oxidative age hardening. In addition, the phase angle reached the same value as aging time reached after approximately 800 h at 60°C in the pressure-aging vessel for AAD-1 and its mixtures with lime. After 800 h of aging, the phase angle was greater for the limetreated asphalt than for the untreated asphalt, and it continued to decrease at a slower rate. This result indicates that the addition of lime to this asphalt increases the initial stiffness of the binder, but, more importantly, it preserves elasticity during long-term oxidative aging. Thus, for this asphalt, at a level of oxidation typical of pavements, limetreated and untreated asphalts arrived at the same viscosity with time, but the lime-treated asphalt had better viscous flow properties than the untreated asphalt. It could then be predicted that the aged, lime-treated asphalt would be more resistant to fatigue cracking. The other asphalt tested (ABD) did not exhibit substantial effects of lime on the rate of oxidative age hardening. This highly compatible, low-asphaltene asphalt is not typical of most paving asphalts. Because hydrated lime has been shown to reduce oxidative age hardening both in the laboratory and during the first few years in the pavement, adding hydrated lime should extend the useful lifetime of most asphalt pavements.

Length-Based Vehicle Classification Schemes and Length Bin Boundaries

2013 ◽  
Vol 2339 (1) ◽  
pp. 19-29 ◽  
Author(s):  
Herbert Weinblatt ◽  
Erik Minge ◽  
Scott Petersen
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
The United States ◽  
Traffic Monitoring ◽  
Vehicle Classification ◽  
Pavement Performance ◽  
Department Of Transportation ◽  
Classification Schemes ◽  
Weigh In Motion

Vehicle classification data are an important component of traffic-monitoring programs. Although most vehicle classification conducted in the United States is axle based, some applications could be supplemented or replaced by length-based data. The typically higher deployment cost and reliability issues associated with collecting axle-based data as compared with length-based data present a challenge. This paper reports on analyses of alternative length-based vehicle classification schemes and appropriate length bin boundaries. The primary analyses use data from a set of 13 Long-Term Pavement Performance weigh-in-motion sites, all in rural areas; additional analyses are conducted with data from 11 Michigan Department of Transportation weigh-in-motion sites located in rural and small urban areas and one site located in an urbanized area. For most states, the recommended length-based vehicle classification scheme is a four-bin scheme (motorcycles, short, medium, and long) with an optional very long bin recommended for use by states in which significant numbers of longer combination vehicles operate.

Properties of Pavement Bitumens Assessed Using European and American Approach

2017 ◽  
Vol 737 ◽  
pp. 554-559
Author(s):  
Pavel Coufalik ◽  
Ondrej Dasek ◽  
Petr Hyzl ◽  
Iva Krcmova
Keyword(s):  
United States Of America ◽  
Fatigue Behavior ◽  
Asphalt Binder ◽  
The United States ◽  
Asphalt Binders ◽  
Short Term ◽  
European Standards ◽  
Unites States ◽  
Key Parameter

This paper compares the different approaches to assessing asphalt binders used in Europe and the Unites States. A series of pavement bitumens is assessed using European standards and also by the Performance Graded Asphalt Binder Specification based on AASHTO MP 1, which was developed as part of the Strategic Highway Research Program (SHRP) in the United States of America. The results show that the European approach places high requirements on the pavement bitumens in relation to their behavior at low-temperatures, while in case of the American approach, the key parameter is fatigue behavior after short-term and long-term aging. It is evident that it is necessary to evaluate properties of pavement bitumens after long-term aging in Europe, too.

Management Considerations for Chronic Asthma

2001 ◽  
Vol 14 (2) ◽  
pp. 108-125
Author(s):  
Sharya Vaughan Bourdet ◽  
Dennis Williams
Keyword(s):  
Inhaled Corticosteroids ◽  
Environmental Control ◽  
Management Strategies ◽  
Asthma Management ◽  
The United States ◽  
Control Measures ◽  
Ongoing Research ◽  
Common Chronic Disease ◽  
Children With Asthma

Asthma is a common chronic disease affecting millions of individuals in the United States. Appropriate management and prevention of asthma symptoms is essential in order to maintain quality of life and reduce healthcare costs. Published consensus guidelines provide recommendations for asthma management and emphasize pharmacologic and nonpharmacologic components for long-term management. Major components of asthma management include environmental control measures, patient education and self-management, pharmacotherapy and periodic assessment. Since publication of the guidelines in 1997, there has been additional research and advances in our knowledge and understanding of asthma. Ongoing research focuses on issues such as regular versus as needed use of short-acting bronchodilators, early initiation of inhaled corticosteroids, safety of inhaled corticosteroids in children with asthma, combination therapy with inhaled corticosteroids and other long-term control agents, and reduction of inhaled corticosteroid doses. Advances in therapy and new knowledge about appropriate management strategies should be incorporated into clinical management strategies.

Establishing National Distributed Network For Long-Term Pavement Performance Information Management System

1997 ◽  
Vol 1592 (1) ◽  
pp. 46-54
Author(s):  
Shared Rowshan ◽  
Sandra B. Harris ◽  
Scott D. Rabinow
Keyword(s):  
Information Management ◽  
Management System ◽  
Information Management System ◽  
The United States ◽  
Database Management System ◽  
Data Availability ◽  
Pavement Performance ◽  
Distributed Network ◽  
Original Design

FHWA’s Long-Term Pavement Performance (LTPP) information management system (IMS) is a relational database management system that has been developed to collect the data necessary to accomplish the goals of the LTPP program established under the Strategic Highway Research Program. The LTPP database and the technology available to collect and manage the data have evolved a great deal since the initial design of the system in 1988. Data from this system are available to users by request by filling out a form. Although some upgrades have been made to hardware and software, a comprehensive evaluation of the computing environment and general IMS procedures had not been performed until the migration analysis. The original design of the LTPP IMS is based on four stand-alone IBM-compatible single-user personal computers transferring data to a minicomputer at the national center that houses all the data collected throughout the United States and Canada. The design concept and some details for the establishment of a national distributed network for the internal operation of the LTPP IMS, intended to migrate to a system that is more compatible with the current hardware and software technology, are described. On the basis of the evaluation of the options considered, cost, technical criteria, and management considerations, the design platform for migration is established as upgrades to Oracle V7, Windows NT, and a national distributed client-server environment. An Integrated Services Digital Network solution is recommended for the network communication. The proposed environment will greatly enhance the data processing and administrative capabilities of the FHWA LTPP IMS. As a result, the data availability and customer service to end users of the data such as state highway agencies would improve.

Cocaine and pregnancy: clinical and toxicological implications for the neonate.

1989 ◽  
Vol 35 (7) ◽  
pp. 1276-1278 ◽  
Author(s):  
I J Chasnoff ◽  
D E Lewis ◽  
D R Griffith ◽  
S Willey
Keyword(s):  
Pregnant Women ◽  
The United States ◽  
Perinatal Complications ◽  
Toxicological Evaluation ◽  
Primary Metabolite ◽  
Ongoing Research ◽  
Drug Free ◽  
Long Term Studies

Abstract Recent studies show that the rate of cocaine use by pregnant women in the United States is much higher than realized hitherto, and an increasing number of infants are being born to cocaine-using mothers. In an ongoing research project to study the effects of cocaine on pregnancy outcome, we studied 70 infants born to cocaine-using women. These infants were matched to a drug-free comparison group selected from the population of the same hospital: children of pregnant women of a similar racial and socioeconomic distribution, but with no history or evidence of licit or illicit drug use during pregnancy. Cocaine-exposed infants had lower birth weight, shorter gestation, and a smaller head circumference than control infants. Cocaine-exposed infants also had neurobehavioral abnormalities at initial evaluation and a higher rate of perinatal complications. Toxicological evaluation of urines of neonates born to cocaine-using women showed that benzoylecgonine, a primary metabolite of cocaine, persisted in the urines for as long as 120 h after delivery. We discuss the role of the immature fetal and neonatal system in the clinical and toxicological outcome of the infant, and emphasize that further long-term studies of this will be needed.

Speech-Language Pathology in the Peace Corps: Necessity and Sustainability

2012 ◽  
Vol 2 (1) ◽  
pp. 11-18
Author(s):  
Melissa A. Pierce
Keyword(s):  
United States ◽  
Special Education ◽  
Peace Corps ◽  
People With Disabilities ◽  
Communication Disorders ◽  
The United States ◽  
Speech Language Pathology ◽  
Speech Language Pathologists ◽  
Language Pathology

In countries other than the United States, the study and practice of speech-language pathology is little known or nonexistent. Recognition of professionals in the field is minimal. Speech-language pathologists in countries where speech-language pathology is a widely recognized and respected profession often seek to share their expertise in places where little support is available for individuals with communication disorders. The Peace Corps offers a unique, long-term volunteer opportunity to people with a variety of backgrounds, including speech-language pathologists. Though Peace Corps programs do not specifically focus on speech-language pathology, many are easily adapted to the profession because they support populations of people with disabilities. This article describes how the needs of local children with communication disorders are readily addressed by a Special Education Peace Corps volunteer.

Multidisciplinary Evidence to Treat Bilingual Individuals with Aphasia

2008 ◽  
Vol 15 (3) ◽  
pp. 66-72 ◽  
Author(s):  
José G. Centeno
Keyword(s):  
Stroke Rehabilitation ◽  
Culturally Diverse ◽  
Treatment Strategies ◽  
The United States ◽  
Intervention Strategies ◽  
Steady Increase ◽  
Clinical Procedures ◽  
Bilingual Speakers ◽  
Aphasic Clients

Abstract The steady increase in linguistic and cultural diversity in the country, including the number of bilingual speakers, has been predicted to continue. Minorities are expected to be the majority by 2042. Strokes, the third leading cause of death and the leading cause of long-term disability in the U.S., are quite prevalent in racial and ethnic minorities, so population estimates underscore the imperative need to develop valid clinical procedures to serve the predicted increase in linguistically and culturally diverse bilingual adults with aphasia in post-stroke rehabilitation. Bilingualism is a complex phenomenon that interconnects culture, cognition, and language; thus, as aphasia is a social phenomenon, treatment of bilingual aphasic persons would benefit from conceptual frameworks that exploit the culture-cognition-language interaction in ways that maximize both linguistic and communicative improvement leading to social re-adaptation. This paper discusses a multidisciplinary evidence-based approach to develop ecologically-valid treatment strategies for bilingual aphasic individuals. Content aims to spark practitioners' interest to explore conceptually broad intervention strategies beyond strictly linguistic domains that would facilitate linguistic gains, communicative interactions, and social functioning. This paper largely emphasizes Spanish-English individuals in the United States. Practitioners, however, are advised to adapt the proposed principles to the unique backgrounds of other bilingual aphasic clients.

Traumatic Brain Injury: A Trauma Surgeon's Perspective

2012 ◽  
Vol 22 (3) ◽  
pp. 82-89
Author(s):  
Oscar D. Guillamondegui
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Multidisciplinary Approach ◽  
Trauma Team ◽  
The United States ◽  
Long Term Outcomes ◽  
Term Care ◽  
Injured Brain ◽  
The Moment

Traumatic brain injury (TBI) is a serious epidemic in the United States. It affects patients of all ages, race, and socioeconomic status (SES). The current care of these patients typically manifests after sequelae have been identified after discharge from the hospital, long after the inciting event. The purpose of this article is to introduce the concept of identification and management of the TBI patient from the moment of injury through long-term care as a multidisciplinary approach. By promoting an awareness of the issues that develop around the acutely injured brain and linking them to long-term outcomes, the trauma team can initiate care early to alter the effect on the patient, family, and community. Hopefully, by describing the care afforded at a trauma center and by a multidisciplinary team, we can bring a better understanding to the armamentarium of methods utilized to treat the difficult population of TBI patients.

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