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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Author: Van Dam, Tom Taylor, Peter Fick, Gary VanGeem, Martha Lorenz, Emily | Size: 22.34 MB | Format:PDF | Quality:Original preprint | Publisher: Iowa State University, Ames | Year: 2012 | pages: 114
Developed as a more detailed follow-up to a 2009 briefing document, Building Sustainable Pavement with Concrete, this guide provides a clear, concise, and cohesive discussion of pavement sustainability concepts and recommended practices for maximizing the sustainability of concrete pavements. The intended audience includes decision makers and practitioners in both owner-agencies and supply, manufacturing, consulting and contractor businesses. Readers will find individual chapters with the most recent technical information and best practices related to concrete pavement design, materials, construction, use/operations, renewal and recycling. In addition readers will find chapters addressing issues specific to pavement sustainability in the urban environment and the evaluation of pavement sustainability.
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An unbonded concrete overlay (UBCO) system is a Portland cement concrete (PCC) overlay that is separated from an existing PCC pavement by an asphalt concrete (AC) interlayer. Current UBCO design procedures are based on empirical equations or highly simplified mechanistic models. To overcome the limitations, fracture mechanics concepts, specifically the finite element method-based cohesive zone model (CZM), are introduced in this research as a new paradigm for analyzing UBCOs with the ultimate goal of establishing a more rational design procedure. To illustrate the advantages of a fracture mechanics-based approach to design, specific attention is paid to but one type of failure associated with pavement structures: reflection cracking. The design against reflection cracking approach relies on a load-carrying capacity equivalency between the designed UBCO and a reference newly designed single layer PCC pavement. An illustrative fracture mechanics-based design procedure for UBCOs is developed and proposed by a large number of crack propagation simulations of both the UBCO composite and the reference single layer pavement. Preliminary comparisons of the results with field observations suggest that the fracture mechanics paradigm offers promise for improved design of UBCOs against reflection cracking and other potential loading conditions that could be analyzed using nonlinear fracture mechanics models. It is recommended that an experimental program be established to assess the accuracy of the model predictions, and additional experiments and three-dimensional fracture mechanics simulations be considered to provide additional insights as to whether UBCOs can be “thinned-up”.
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This research investigated the effects of changing the cementitious content required at a given water-to-cement ratio (w/c) on workability, strength, and durability of a concrete mixture. An experimental program was conducted in which 64 concrete mixtures with w/c ranging between 0.35 and 0.50, cementitious content ranging from 400 to 700 per cubic yard (pcy), and containing four different supplementary cementitious material (SCM) combinations were tested. The fine-aggregate to total-aggregate ratio was fixed at 0.42 and the void content of combined aggregates was held constant for all the mixtures. Fresh (i.e., slump, unit weight, air content, and setting time) and hardened properties (i.e., compressive strength, chloride penetrability, and air permeability) were determined. The hypothesis behind this study is that when other parameters are kept constant, concrete properties such as strength, chloride penetration, and air permeability will not be improved significantly by increasing the cement after a minimum cement content is used. The study found that about 1.5 times more paste is required than voids between the aggregates to obtain a minimum workability. Below this value, water-reducing admixtures are of no benefit. Increasing paste thereafter increased workability. In addition, for a given w/c, increasing cementitious content does not significantly improve compressive strength once the critical minimum has been provided. The critical value is about twice the voids content of the aggregate system. Finally, for a given w/c, increasing paste content increases chloride penetrability and air permeability.
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The focus of this project was on identifying critical properties that control long‐term performance of repair concrete, especially rapid-setting materials extended using pea gravel (maximum size aggregate 9.5 mm). In the first phase of this project, four commercial rapid‐setting materials (CRSMs) were selected and development of mixture proportions in terms of optimum pea gravel content and water content was performed. Optimized mixtures were further evaluated at three different initial temperature conditions. The properties evaluated included workability, setting time, rate of compressive strength developed, slant shear bond strength, freeze‐thaw resistance, air‐void system characteristics of hardened concrete, drying shrinkage and cracking potential. It was observed that some of the CRSMs evaluated did not meet requirements of ASTM C 928. All, except one, CRSMs tested exhibited low resistance to freezing and thawing but all had high resistance to cracking. In the second phase of the project, rapid‐setting self‐consolidating concrete (RSSCC) was developed using ternary blend of cementitious materials, high‐range water reducer (HRWR) and accelerators. Slump flow, visual stability index (VSI), compressive strength at various ages and the power consumption values for the mortar mixer indicated that a five minutes mixing sequence involving a 2‐Step addition of HRWR produces stable RSSCC mixture. The results of various tests carried out indicate that it is possible to develop a small aggregate size‐based self‐consolidating repair concrete that achieves a compressive strength of 19 MPa at the end of 6 hrs, has good bond characteristics and excellent freezing and thawing durability (DF>90%). The sensitivity of RSSCC to aggregate characteristics and production variables was also evaluated. Specifically, the influence of aggregate gradation and aggregate moisture content using different types of mixers and re‐mixing after a period of rest was evaluated. It was observed that variation in aggregate moisture content and aggregate gradation resulted in noticeable changes in fresh concrete properties such as the slump flow, stability and V‐funnel flow values. While changes in moisture content and gradation of aggregates had an impact on the early (6 h) compressive strength, the compressive strength at the end of 24 hours was not significantly affected.
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The main issue associated with this research is if cheaper alternatives can be configured for subbase construction. Subbase layers have certain functions that need to be fulfilled in order to assure adequate pavement performance. One key aspect is resistance to erosion, and assessment of each of these functions relative to different alternatives is key to understanding the capability of different alternatives to perform adequately. In this respect, this project was poised to examine the design assumptions associated with each alternative and provide design recommendations accordingly to include test methods and material specifications. This report describes some of the work accomplished by summarizing data on subbase performance and testing relative to concrete pavement subbase and subgrade erosion but mainly addresses guidelines for concrete pavement subbase design. Findings from field investigations are discussed to identify factors associated with erosion. An approach to mechanistically consider the erosion process was introduced and review of current design procedures was conducted to reveal how they address erosion. This review was extended to include erosion models described in the literature as a means to shed light on the relationship between measurable material properties and performance. Additionally, past and current design procedures relative to erosion were reviewed in terms of test methods, erosion models, and their utility to characterize subbase materials with respect to erosion resistance. With this information, a new test configuration was devised that uses a rapid tri-axial test and a Hamburg wheel-tracking device for evaluating erodibility with respect to the subbase type and degree of stabilization (cement content). Test devices, procedures, and results are explained and summarized for application in mechanistic design processes. A proposed erosion model was validated by comparing erosion predictions to erosion results. Several computer program analyses were conducted to assess the design and performance implications of different subbases alternatives. Guidelines are provided to promote economical and sustainable design of concrete pavement subbases.
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WhiteSmoke is an all-in-one English writing tool that provides grammar, spelling, punctuation and style checks. Integrated into WhiteSmoke are world-renowned word and text translation and document templates. WhiteSmoke is activated in a single click from any text application and browser. It is an added-value product that ensures a higher standard of English writing. Corporations, governments, academic institutions and individuals throughout the world use WhiteSmoke to enhance their daily communication. WhiteSmoke encourages the writing process, calls out potential errors for consideration, and offers suggestions for improvement. WhiteSmoke is suitable for everyone, including native and non-native speakers. It is the most versatile and powerful program of its kind, catching more errors than any other program, including the most popular word processing programs. At home, in the office or on the go--WhiteSmoke guarantees all your daily correspondence is error free.
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