14 research outputs found
Evaluating the Need to Seal Thermal Cracks in Alaska’s Asphalt Concrete Pavements
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Early age delamination in concrete pavements made with gravel aggregates
Get PDFGravel aggregates had been used extensively in the Houston District of Texas Department of Transportation (TxDOT) for continuously reinforced concrete pavements construction for many years. However, some of these pavements have been subject to early age delamination and eventual spalling damage. Therefore, a series of studies funded by TxDOT since the early 1990's has been conducted to gain a better understanding of mechanisms, material properties, and construction practices, and to provide guidelines and recommendations for minimizing early-age delamination in concrete pavements made with gravel aggregates. In this study, a test protocol to measure the bond strength between aggregates and cement mortar was established, and the effects of different material and construction parameters on the bond strength of concrete at early ages using a fractional factorial design were investigated. The significances of each factor to achieve better bonding performance were determined, and the optimum design combination was subsequently chosen and validated. Geometric parameters were proposed to characterize aggregate shape properties relative to bonding performance with the facilitation of the Aggregate Imaging System. A rating system based on utility theory was developed to evaluate the overall contribution of aggregate properties (i.e. physical, geometric, and chemical) to the concrete bonding capability and the feasibility of certain mixture design combinations. As for theoretical representation of the bond strength across the interfacial transition zone, a model of interfacial fracture energy between aggregate and mortar that represents the energy necessary to create a crack along the interface was formulated. This model built the connection between concrete properties at the meso-level (represented by the interfacial fracture energy between aggregate and mortar) and the macro-level (represented by fracture toughness of concrete and significant influencing materials and construction factors). In addition, the moisture effects on stress development of concrete pavements at early ages using field data as inputs were numerically simulated, and a fracture mechanics-based approach was used to predict the occurrence of delamination. A delamination detection protocol for the field was developed to explore the feasibility and potential of utilizing Ground Penetration Radar technology in delamination detection. Research findings from laboratory investigation, field testing, theoretical modeling, and numerical analysis were further validated through field test sections, and the associated framework for delamination guidelines was established
Tool developing of MRR strategy selection
No full textDue to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 74-77).Issued also on microfiche from Lange Micrographics.Better decision-making processes, guidelines, and tools to select MRR (maintenance, rehabilitation, and reconstruction) strategies are very necessary for SHAs (state highway agencies) to evaluate the effectiveness of their MRR strategies and treatments in order to better maintain and preserve the nation's highways. The purpose of this study is to present a spreadsheet-type analysis program, an automation of MRR strategy selection, to assist in the overall selection process. The utility theory is utilized through all strategy selection procedures and the automation relies upon a rating process that balances factors that influence the selection of MRR strategies. These factors include pavement treatment and material selection, safety, constructibility, construction and traffic control cost, corridor impact, and road user delay. Three main tasks are involved in the decision process and accomplished by related programming tools. Task 1 is to assess pavement condition data and develop key evaluation indicators to identify the strategy type (i.e. routine maintenance, CPR (concrete pavement restoration), overlay, or construction). Task 2 develops feasible strategies from a list of possible strategies and determines the level of MRR that is to be carried out in this process along with required additional pavement condition data to select the feasible treatment combinations. In this part, treatment combinations (including assessment of remaining life and life extension relative to cracking, spalling, faulting and roughness in concrete pavements and reflective cracking, rutting, and delamination in asphalt overlay of concrete pavements) are modelled, and traffic level, time of construction, and corresponding first cost are estimated. In Task 3, life cycle cost, non-agency cost, corridor impact, and constructibility are assessed for the selection of the most preferred strategy for the project. The data used in demonstrating the process is taken from an actual site in Arkansas on I-30W near Texarkana. Through the whole selection procedure it is evident that both preferred MRR strategy for pavement and techniques for optimizing the service life of the pavement in terms of cost and performance are accomplished. In the conclusion of the thesis, possible improvements and further extensions to the present strategy selection program are discussed
Work Plan for Special Design Features & Crack Sealing Maintenance for Parks Highway
No full textINE/AUTC 14.0
