Synthesis of Performance Testing of Asphalt Concrete
Author: Dave, Eshan V Koktan, Philip | Size: 678 KB | Format:PDF | Quality:Original preprint | Publisher: University of Minnesota, Duluth | Year: 2011 | pages: 90
At present, like many other agencies, the Minnesota Department of Transportation asphalt material specifications rely primarily on volumetric properties to ensure good field performance. There have been considerable amounts of research efforts to develop so called “asphalt performance tests” that can link laboratory-measured parameters to pavement performance. Research efforts are also undertaken to refine the asphalt mix-design method so that laboratory tests and procedures can be incorporated into material specification. This research project explored availability of such tests, their suitability, and their use by other agencies.
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Finite Element Analysis of Deep Wide-Flanged Pre-stressed Girders to Understand and Control End Cracking
Author: Oliva, Michael G University of Wisconsin, Madison Okumus, Pinar | Size: 9.48 MB | Format:PDF | Quality:Original preprint | Publisher: University of Wisconsin, Madison | Year: 2011 | pages: 132
Hundreds of prestressed concrete girders are used each year for building bridges in Wisconsin. The prestress transfer from the prestressing strands to concrete takes place at the girder ends. Characteristic cracks form in this end region during or immediately after detensioning. Potential solutions to control end cracking were examined via finite element models and the impact of each solution on cracking was evaluated. Modifications to reinforcement bar size, debonding ratios, strand cutting sequence and use of draped strand patterns were simulated by the models. The results from different analyses were compared to quantify the success of each method in reducing strains causing girder end cracks. The tension strains leading to cracks of all types were responsive to debonding some of the bottom flange prestressing strands. Bottom flange cracking can be prevented by methodically debonding exterior strands, keeping the draped strands bonded, and evenly distributing the remaining bonded strands over the bottom flange.
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Numerical Modeling and Experimental Investigation of the Local Hydrology of a Porous Concrete Site
Author: Syrrakou, Christina Pinder, George | Size: 9.56 MB | Format:PDF | Quality:Original preprint | Publisher: University of Vermont, Burlington | Year: 2011 | pages: 86
Although porous pavement use has been accepted as a successful stormwater management practice in warm climates, application in regions with colder climates, like New England, is still under investigation. The Randolph Park and Ride Site, which is the area of interest of this specific study, is the first porous concrete site constructed in Vermont. The site, which was built in 2008 and is under use up to today, is quite unique in terms of the geology of the underlying materials and also the extensive instrumentation that has been applied in the field. The purpose of building this site was in part commercial, to provide the town of Randolph with a public parking lot, and part experimental, aimed at giving insight to the optimal design of porous pavements in New England. This study focuses on the experimental use of the site. The study initially aims at investigating the interaction between porous concrete utilization and local hydrology at porous concrete sites in New England. With this part achieved, a mathematical model can be developed and used prior to construction as a design tool for other porous concrete sites. It is also a secondary goal of this study to combine the mathematical model created with an optimization algorithm that will allow for optimal design of porous concrete sites in terms of minimal expense.
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The Texas Department of Transportation (TxDOT) has approximately 50,000 bridges in its inventory and the deterioration of concrete under these bridges, most of which are reinforced, has been a critical issue affecting the service condition. Recent research on deteriorated concrete columns on bridges in Texas indicated that microbial colonization might be a factor promoting the surface deterioration of bridge columns continuously exposed to water. Although microbial activities may be involved in the surface deterioration, it is however not clear how severe the deterioration is and whether it is a significant contributor to the deterioration. Field and laboratory investigations are needed to identify the impact of microbial induced deterioration (MID) on TxDOT bridges. To evaluate the severity of the deterioration and determine whether MID is a significant contributor to the deterioration, visual inspection and a number of in situ tests were performed on columns of twelve selected TxDOT bridges. Laboratory tests including microbial, chemical composition, mineralogy and petrographic analyses were performed to investigate the potential cause and extent of the deterioration. Results from this comprehensive study were used to provide evidence of concrete degradation and ascertain the degree of deterioration caused by microbial attack. The study also evaluated the effectiveness and consistency of various measurements used in this study and provided a suggested test procedure to identify microbial attack on concrete and evaluate the integrity of deteriorated concrete due to the attack. In addition, a preliminary evaluation of the microbial attack resistance of commonly used TxDOT mixes was performed through evaluation of resistance of a series of mixes subjected to field and/or sulfuric acid solution exposure.
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Development of Criteria for Using the Superpave Gyratory Compactor to Design Airport Asphalt Pavement Mixtures
Author: Rushing, John F | Size: 1.57 MB | Format:PDF | Quality:Original preprint | Publisher: U.S. Army Engineer Research and Development Center | Year: 2011 | pages: 247
Asphalt mix design for commercial airports in the United States is performed in accordance with guidelines set forth in the Federal Aviation Administration (FAA) Advisory Circular AC 150/5370-10D, “Standard for Specifying Construction of Airports, Item P-401—Plant Mix Bituminous Pavements.” Currently, two methods are used to compact asphalt pavement mixtures used in transportation surfaces. The Marshall method, the standard method for commercial airports, uses an impact device that imparts a repetitive stress to the mixture. The Superpave design method provides a kneading action to compact the mixture under constant strain conditions. Design of asphalt mixtures for airfields has been successfully accomplished using the Marshall method since the 1940s. The Superpave design method was developed and adopted by state departments of transportation beginning in the mid-1990s. Currently, most transportation departments have adopted this concept. Since most of the paving work by the asphalt industry is funded by state departments of transportation and private work (which typically use department of transportation criteria), it is becoming more difficult to find laboratories and contractors that continue to use the Marshall method. Hence, it is important that the Superpave method be adopted for airfield pavements. Prior to adopting Superpave as the primary method, it was necessary to determine the number of gyrations required to provide an adequate compactive effort for airfield pavements. This study evaluated the number of gyrations for a number of mixtures required to provide a density equal to 75 blows with the Marshall hammer. Since the 75-blow Marshall mixtures had performed well in the past, it was believed that providing a density with the gyratory compactor equal to that obtained with Marshall compaction would be a good way to adopt Superpave and still have confidence of good performance. This report describes the details of the study and provides a recommended number of gyrations with the Superpave gyratory compactor to provide a mixture that will perform similar to the 75-blow Marshall mixture. The study recommended that 70 gyrations are required to produce a mix similar to the 75-blow Marshall mixture. Additional research is also needed to correlate field performance of asphalt mixtures designed using Superpave methodologies.
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Finite Element Evaluation of Pervious Concrete Pavement for Roadway Shoulders
Author: Alam, Ashraful Haselbach, Liv Washington State University, Pullman Cofer, William Washington State University, Pullman | Size: 2.16 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Northwest Regional Center X (TransNow) | Year: 2011 | pages: 79
Stormwater quantity control is an important issue that needs to be addressed in roadway and ancillary transportation facility design. Pervious concrete has provided an effective solution for storm runoff for parking lots, sidewalks, bike trails, and other applications. It should be readily adaptable for use on roadway shoulders. Being a relatively new material for use in pavement for roadways, there is a lack of knowledge of the strength and behavior of pervious concrete slabs. While standard procedures for rigid pavement design with Portland cement concrete have been recommended, there are fundamental differences with pervious concrete pavement. These include a variation in concrete strength and stiffness through the depth of a slab and differences in the subgrade. Also, the main concern for a shoulder is the need to withstand wheel loadings from encroaching truck traffic. Both the strength of the pervious concrete pavement and the interface with the mainline pavement must be evaluated. Typically, tiebars are used at the interface to connect the shoulder and mainline slabs. The capacity and durability of pervious concrete at the tiebars is unknown, and steel reinforcing may not be an option with pervious systems. While full-scale testing of pervious concrete pavement is desirable, a preliminary evaluation can be performed quickly and economically through computer simulation. The Finite Element Method is a proven technique for the evaluation of solids and structures. With this approach, a number of loading scenarios can be applied to various pavement configurations to determine pavement capacity and evaluate the importance of connections with tiebars. The results of these analyses can be used to guide a full-scale testing program and help develop design procedures.
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Simplifying Bridge Expansion Joint Design and Maintenance
Author: Caicedo, Juan M University of South Carolina, Columbia Wieger, Glen Ziehl, Paul Rizos, Dimitris | Size: 1.84 MB | Format:PDF | Quality:Original preprint | Publisher: University of South Carolina, Columbia | Year: 2011 | pages: 57
This report presents a study focused on identifying the most durable expansion joints for the South Carolina Department of Transportation (SCDOT). This is performed by proposing a degradation model for the expansion joints and updating it based on bridge inspections. Open expansion joints and pourable joint seal were found to be the best performing joints based on the proposed degradation models. Assembly joints and compression joint seal have an intermediate performance and strip seal expansion joints have the lowest performance of the type of expansion joints studied. Assembly joints are found to be problematic because of the different moving parts composing the joint. A significant number of bridge joint failures are caused because of incorrect installation, in particular, joints with complex anchor systems between the bridge deck and expansion joint. The SCDOT standards were found to be up to date and comparable to other Department of Transportation standards in terms of the design and installation aspects of bridge joints. A recommendation is made to request a warranty for the installation when appropriate. Other general best practices during the installation of the expansion joint include: 1) when possible, install joints when the ambient temperature is the average of the range of temperatures in the area. This allows the joint to be installed close to the “undeformed” position of the bridge; 2) the support of the joint should be installed in good quality, cured concrete; and 3) avoid splices of any pre-manufactured material. If splices cannot be avoided, place the splice outside the wheel path.
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Evaluation of The In-Service Safety Performance of Safety-Shape and Vertical Concrete Barriers
Author: Albuquerque, Francisco Daniel B | Size: 922 KB | Format:PDF | Quality:Original preprint | Publisher: University of Nebraska, Lincoln | Year: 2012 | pages: 166
Roadside concrete barriers have been widely used to protect errant motorists from hitting roadside hazards or obstacles. Two concrete barrier profiles, vertical and safety-shape, have been used for this purpose. The safety-shape profile has been shown to produce excessive vehicle climbing which tends to increase rollover propensity. On the other hand, the vertical profile does not cause vehicle climbing, but it does produce higher lateral forces which may produce higher injury levels. The objective of this research is to investigate which barrier profile is the safest based on real-world vehicle crash data. The safest barrier profile is defined as the one that produces lower injury levels. Rollover propensity was also used as a second indicator of barrier performance since rollovers may also affect injury severity. Bridge-related crash data was collected from State maintained highways in the State of Iowa. It was found that rollovers are twice more likely to occur in crashes involving safety-shape barriers as compared to vertical barriers. It was also found that crashes that involved safety-shape barriers resulted in higher injury levels as compared to crashes that involved the vertical barriers. Therefore, it is believed that the expanded use of vertical barriers would improve overall highway safety.
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Characterization of Aggregates for Sustainable Freight Transportation Infrastructure
Author: Titi, Hani H Druckrey, Andrew Alshibli, Khalid Horowitz, Alan J | Size: 47.97 MB | Format:PDF | Quality:Original preprint | Publisher: University of Wisconsin, Milwaukee | Year: 2012 | pages: 155
A novel method, X-ray computed tomography (CT), has recently emerged as a powerful, nondestructive methodology for material characterization, including geomaterials. This method produces 3D images of the object that can be analyzed in various ways based on the purpose of the scan. The objective of this research is to use X-ray CT technology to investigate the internal structure and porosity of various types of aggregates such as limestone, granite, and quartzite. In addition, this research used X-ray CT technology to investigate the influence of harsh environments such as freezing and thawing on the durability of the aggregate. Virgin and treated aggregate specimens were subjected to X-ray CT to obtain high-resolution 3D images. Aggregate treatments (wetting/drying and freeze-thaw cycles) were conducted using the sodium sulfate soundness test and the actual free-thaw test. The CT scans were carried out using a sector 13-BMD synchrotron microtomography beamline at the Advanced Photon Source of the Argonne National Laboratory, Illinois. Analysis was conducted on the acquired 3D high-resolution images to investigate the pore structure and micro-cracks of these aggregates types. The X-ray CT technology was useful for visualizing the internal structure of aggregate particles with high resolution. This visual inspection provided information on pore space characteristics such as pore shape, connectivity, and distribution. In addition, volumetric quantities such as the volume of aggregate particles and the volume of pore space were identified and measured. These measured quantities were used to calculate porosities of the investigated aggregates, which provided properties of these aggregates using the constructed 3D CT images (non-conventional method). Sodium sulfate soundness test effects on the treated aggregates (degradation, disintegration, and weathering) were significant, as observed in the 3D CT images of treated aggregate particles. Pore space volume increased as the aggregate particles were treated with wetting/drying cycles of sodium sulfate solution. The sodium sulfate soundness test significantly affected the permeable (connected) pore space and induced degradation/disintegration, which increased the volume of connected pore space with the increase of the number of wetting/drying test cycles. Isolated pore space remained unchanged with the number of sodium sulfate test cycles, since the salt could not penetrate these pores to induce internal force of expansion, which degraded and disintegrated the aggregate structure. The freeze-thaw test induced changes to the pore space of the treated aggregates with a noticeable impact on the connected pore space of the aggregate particle.
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This PDF contains the 202 slides from a presentation about full-depth and partial-depth repair of continuously reinforced concrete pavement.
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