Louisiana Transportation Research Center

New Orleans, LA, United States

Louisiana Transportation Research Center

New Orleans, LA, United States
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Cooper S.B.,Louisiana Transportation Research Center | Mohammad L.N.,Louisiana State University | Elseifi M.A.,Louisiana State University
Journal of Materials in Civil Engineering | Year: 2017

As the price of liquid asphalt continuously climbs, methods are being sought to decrease material costs without compromising material or pavement performance while having a positive influence on sustainability. One potential method is the use of recycled materials, such as recycled asphalt shingles (RAS) and reclaimed asphalt pavements (RAP). The objective of this study was to characterize the laboratory performance of conventional asphalt mixtures and mixtures containing RAP and/or RAS, with and without recycling agents (RAs). The RAS type utilized in this study was postconsumer waste shingles. Six 12.5-mm asphalt mixtures were designed to meet certain criteria with four of the six mixtures containing no RAs and two mixtures containing RAs [Hydrogreen and soft asphalt binder (Asphalt & Wax Innovations, Pass Christian, Mississippi)]. A suite of laboratory tests was used to ascertain the mechanistic behavior of the mixtures evaluated against major distresses. Laboratory testing evaluated the high-, intermediate-, and low-temperature properties of laboratory produced mixtures using the Hamburg loaded-wheel tester, the semicircular bending test, and the thermal stress restrained specimen test in addition to the dynamic modulus test. Results indicated that the use of RAs improved the blending between aged and virgin binders, which adversely affected the intermediate- and low-temperature performance of the mixture. With the increase in availability of aged binder in the mix, the inclusion of RAP and/or RAS with and without RAs showed an improvement in rutting performance. © 2016 American Society of Civil Engineers.

Gopu V.,Louisiana Transportation Research Center | Gopu V.,University of Louisiana at Lafayette
Insights and Innovations in Structural Engineering, Mechanics and Computation - Proceedings of the 6th International Conference on Structural Engineering, Mechanics and Computation, SEMC 2016 | Year: 2016

Timber bridges are used extensively on secondary roads in the U.S. and account for nearly 10 percent of the half-a-million bridges in the National Bridge Inventory (NBI) database. Since the NBI database considers only bridges with timber in the superstructure as a timber bridge, the overall number of bridges that utilize timber in the super-or sub-structure is significantly higher than 10 percent. Timber bridges are popular because of the ease of construction, lower construction costs and not needing specialty contractors or heavy equipment. A vast majority of the timber bridges have been in service for 30-60 years and nearly half of all these timber bridges are structurally deficient or functionally obsolete. The primary reason for this high level of deficiency in these bridges is the failure to incorporate construction details and practices that inhibit the adverse impacts of the environment and biological infestation. The service life of a properly constructed timber bridge is comparable or better than that of a concrete or steel bridge. This paper presents an overview of a study undertaken by the author to assess the condition of timber bridges in the Southeastern United States and identify the factors that are adversely impacting their durability, performance and load rating. Load posting of these timber bridges causes havoc for the rural communities that are dependent of this transportation lifeline. Giving a severely strained transportation funding program, replacing the numerous deteriorated timber bridges is neither affordable nor viable. The current scenario offers an excellent opportunity to deploy FRP composites in the repair and rehabilitation of deteriorated timber bridges to restore their load rating and avoid the prohibitive cost of replacing these bridges. The effective FRP repair and rehabilitation methods are discussed and examples of presented. The challenges associated with using FRP for timber bridge repair are discussed and recommendations are made for restoring/enhancing the load rating of the bridges. © 2016 Taylor & Francis Group, London.

Cooper S.B.,Louisiana Transportation Research Center | Mohammad L.N.,Louisiana State University | Elseifi M.A.,Louisiana State University
Journal of Materials in Civil Engineering | Year: 2017

The use of recycled materials, such as recycled asphalt shingles (RAS), has received considerable attention for its potential to decrease production costs and enhance the sustainability of paving operations. The objective of this study was to characterize the laboratory performance of asphalt mixtures containing RAS with and without re-refined engine oil bottoms (REOB) used as a recycling agent (RA). The RAS type used in this study was postconsumer waste shingles (PCWS). Five 12.5-mm asphalt mixtures were designed to meet Superior Performing Asphalt Pavements (Superpave) design criteria, with two containing no REOB and three containing various amounts. A suite of laboratory tests was used to ascertain the mechanistic behavior of the mixtures against major distresses. Laboratory testing evaluated the high-, intermediate-, and low-temperature properties of laboratory-produced mixtures using the Hamburg loaded-wheel tester (LWT), the semicircular bend (SCB) test, and the thermal stress restrained specimen test (TSRST). For the mixtures evaluated, results indicated that the use of REOB increased the recycled binder ratio, which adversely affected intermediate-temperature fracture resistance. Although the inclusion of 5% RAS and 5% REOB did not adversely affect low-temperature performance; TSRST results showed that as the percentage of REOB increased, low-temperature fracture performance decreased. On the other hand, rutting performance was comparable for the control mixture and the mixtures containing RAS and REOB. © 2017 American Society of Civil Engineers.

Mohammad L.N.,Louisiana State University | Cooper S.B.,Louisiana Transportation Research Center
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions | Year: 2016

Conventional asphalt mixture design methodologies such as Superpave, Marshall, and Hveem are used to determine the optimum asphalt binder content by means of physical and volumetric laboratory measurements. All three procedures ensure the materials proportion and quantity of the asphalt cement binder are adequate to meet stability and durability concerns. However, with the increased use of recycled materials, there is a need to develop laboratory mechanical tests in order to evaluate the quality of the asphalt cement binder to complement the Superpave volumetric mixture design procedure. An important component to successful mixture design is the balance between volumetric composition and material compatibility. Balanced asphalt mixture design offers innovation in designing mixtures for performance and evaluation of the quality of a mix design relative to the anticipated performance using a rational approach. This research documents the selection of laboratory mechanical tests, in addition to volumetric requirements, that can ascertain a mixture's resistance to common asphalt pavement distresses. Factors in the selection of laboratory mechanical tests such as availability of standard test procedures, advantages and limitations, laboratory-to-field correlations, and sensitivity to mixture composition are reviewed. Further, an implementation framework and case histories is also discussed. © 2016, Association of Asphalt Paving Technologist. All rights reserved.

Nazzal M.D.,Ohio University | Abu-Farsakh M.Y.,Louisiana Transportation Research Center | Mohammad L.N.,Louisiana State University
International Journal of Geomechanics | Year: 2010

A finite-element model was developed using ABAQUS software package to investigate the effect of placing geosynthetic reinforcement within the base course layer on the response of a flexible pavement structure. A critical state two-surface constitutive model was first modified to represent the behavior of base course materials under the unsaturated field conditions. The modified model was then implemented into ABAQUS through a user defined subroutine, UMAT. The implemented model was validated using the results of laboratory triaxial tests. Finite-element analyses were then conducted on different unreinforced and geosynthetic reinforced flexible pavement sections. The results of this study demonstrated the ability of the modified critical state two-surface constitutive model to predict, with good accuracy, the response of the considered base course material at its optimum field conditions when subjected to cyclic as well as static loads. The results of the finite-element analyses showed that the geosynthetic reinforcement reduced the lateral strains within the base course and subgrade layers. Furthermore, the inclusion of the geosynthetic layer resulted in a significant reduction in the vertical and shear strains at the top of the subgrade layer. The improvement of the geosynthetic layer was found to be more pronounced in the development of the plastic strains rather than the resilient strains. The reinforcement benefits were enhanced as its elastic modulus increased. © 2010 ASCE.

Hassan M.M.,Louisiana State University | Dylla H.,Louisiana State University | Mohammad L.N.,Engineering Materials Characterization Research Facility | Rupnow T.,Louisiana Transportation Research Center
Construction and Building Materials | Year: 2010

The use of titanium dioxide (TiO2) ultrafine particles as coating for concrete pavement have received considerable attention in recent years as these particles can trap and decompose organic and inorganic air pollutants by a photocatalytic process. In spite of these promising benefits, the durability and resistance to wear of TiO2 surface coating has not been evaluated. The objective of this study was to determine the abrasion and wear resistance properties of TiO2 coatings and its effect on the coating's environmental performance. To achieve this objective, an experimental program was conducted to measure and compare the environmental performance of titanium dioxide coating before and after laboratory-simulated abrasion and wearing. The environmental efficiency of the coating to remove nitrogen oxides (NOx) from the atmosphere was measured using a newly developed laboratory setup. Microscopic analysis was conducted using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to determine the distribution of TiO2 particles on the surface before and after wearing. The measured rut depth using the Loaded-Wheel Tester (LWT) was minimal indicating that the use of the coating did not appear to affect the wear resistance of the surface. Wearing of the specimens with 5% TiO2 resulted in a small decrease in the coating NO removal efficiency. In contrast, the wearing of the samples with 3% TiO2 slightly improved the NO removal efficiency. Results presented in this paper support that the use of TiO2 coating as a photocatalytic compound would provide acceptable durability and wear resistance.

Yu X.B.,Case Western Reserve University | Yu X.B.,Louisiana Transportation Research Center | Yu X.,Case Western Reserve University
Canadian Geotechnical Journal | Year: 2011

Bridge scour is a major threat to the safety of bridges. There is a high risk of scour-induced damage due to the catastrophic nature of bridge foundation failure. The development of an innovative bridge scour monitoring system is a pressing task for the research community. Such a system needs to be fieldworthy, which is a characteristic assessed in terms of accuracy, ruggedness, and automation. Among these criteria, an automatic signal analysis algorithm is generally a prerequisite for deploying a long-term field monitoring program. This paper describes the development and validation of an algorithm for a scour monitoring system based on the principles of guided radar: time-domain reflectometry (TDR). This algorithm is based on the extension of the classic dielectric mixing model to layered systems. The performance of this algorithm is evaluated using experiments designed to simulate different field scour conditions. These include different types of sediments and the variation of river conditions (i.e., salinity of river water, air entrainment, and amount of suspended sediments). The experiment results indicate that the developed analyses algorithm is robust and accurate for scour-depth estimation under these investigated conditions.

Saber A.,Louisiana Tech University | Alaywan W.,Louisiana Transportation Research Center
Journal of Bridge Engineering | Year: 2011

Continuity diaphragms used in prestressed girder bridges on skewed bents have caused difficulties in detailing and construction. The results of the field verification for the effectiveness of continuity diaphragms for skewed, continuous, and prestressed concrete girder bridges are presented. The current design concept and bridge parameters that were considered include skew angle and the ratio of beam spacing to span (aspect ratio). A prestressed concrete bridge with continuity diaphragms and a skewed angle of 48°was selected for full-scale test by a team of engineers from Louisiana Department of Transportation and Development and the Federal Highway Administration. The live load tests performed with a comprehensive instrumentation plan provided a fundamental understanding of the load transfer mechanism through these diaphragms. The findings indicated that the effects of the continuity diaphragms were negligible and they can be eliminated. The superstructure of the bridge could be designed with link slab. Thus, the bridge deck would provide the continuity over the support, improve the riding quality, enhance the structural redundancy, and reduce the expansion joint installation and maintenance costs. © 2011 ASCE.

Yu X.,Case Western Reserve University | Yu X.,Louisiana Transportation Research Center
Advances in Structural Engineering | Year: 2011

Bridge scour is the number one cause of bridge failures. There are high risks associated with scour-induced damages due to their catastrophic nature. Developing real time bridge scour monitoring systems is a pressing task for the research community. Such systems need to be accurate, rugged, and field worthy. Implementing automatic signal interpretation is important to ensure the success of a long term scour monitoring instrument. This paper is part of the efforts to develop a TDR system to monitor the development of scour and sedimentation process. The focus of this paper is on an automation algorithm for TDR signal analyses. It discusses the theoretical foundation of this TDR algorithm for scour depth estimation. The influence of different types of sediments and the conditions of river (including the salinity and the effects of high air entrainment and suspended sediments) on the accuracy are assessed. The study indicates that the scour monitoring algorithm based on extending a physics-based general design equation is accurate under these different conditions. This will help implement a robust algorithm to automate the TDR bridge scour monitoring system.

Agency: NSF | Branch: Standard Grant | Program: | Phase: IUSE | Award Amount: 337.31K | Year: 2015

The University of New Orleans (UNO), Louisiana State University (LSU) and the Louisiana Transportation Research Center (LTRC) are partnering on the project Field Monitoring and Measurements Education: A Model for Civil and Environmental Engineering. The goal of this project is to develop a model instructional program, using structural engineering and structural health monitoring as a test bed, that can be used to educate civil and environmental engineering (CEE) students in the fundamental principles and technology of field monitoring and measurements (FMM) and to utilize monitoring technologies and FMM data to evaluate performance and behavior, analyze problems and design CEE systems. The nations aging, and in some cases, failing infrastructure necessitates the education of future engineers to address problems related to structural health (and other critical areas). Since this project addresses a national need, two activities will be given significant attention: developing and implementing the instructional materials in a manner that maximizes their potential for adoption at other institutions; and building a community of interested and contributing scholars. The latter effort will encompass targeted proactive outreach activities at the state, regional, and national levels.

Specific objectives of the project are to: (1) improve student performance with respect to the existing learning outcomes of the civil engineering courses into which field monitoring modules will be incorporated, (2) improve student knowledge of and ability to use field monitoring measurements, (3) train faculty in the use of the curricular materials and (4) develop a community of scholars that has an interest in and will contribute to the further development of FMM instructional materials. Quality control and quality assurance of the instructional materials will be achieved through close coordination among the investigators, the advisory panel, and the external evaluator aided by the results of a formative evaluation of the prototype structural engineering FMM instructional unit and a summative evaluation of a revised unit over a two academic year cycle at both LSU and UNO. During the second year of the project, the unit will be introduced and assessed at four partner institutions (Virginia Tech, Case Western Reserve University, Tuskegee University and University of North Florida). The project collaborators at the partner institutions will also be used in an advisory capacity throughout all stages of the project. The results of this project will serve to establish an instructional model upon which other CEE sub-disciplines can build.

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