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Author: Stacey D. Diefenderfer Publisher: ISBN: Category : Pavements, Asphalt Languages : en Pages : 44
Book Description
Several processes have been developed to reduce the mixing and compaction temperatures of hot mix asphalt (HMA) without sacrificing the quality of the resulting pavement. The purpose of this study was to evaluate the installation of warm mix asphalt (WMA) to compile experiences and offer recommendations for future use. Three trial sections were installed using warm mix technologies between August and November of 2006. Two used the Sasobit technology, and the third employed the Evotherm technology. This report discusses the material makeup of these technologies and documents the production and placement of the three trial sections. The results of this study and further studies can serve as a basis for decision making by the Virginia Department of Transportation (VDOT) regarding the use of WMA technology. Trial sections were initiated through cooperative efforts by the Virginia Transportation Research Council; VDOT districts, residencies, and area headquarters; and participating contractors. Construction used typical mixture designs and practices so that performance under typical construction conditions could be evaluated. General experiences and processes used during construction were documented, and samples were taken for laboratory characterization. Density measurements and cores were taken at each site to determine the initial pavement properties. At the Evotherm installation, asphalt fume sampling was conducted by VDOT's Employee Safety & Health Division to evaluate differences in worker exposure between HMA and WMA pavement laydown operations. The study showed that WMA can be successfully placed using conventional HMA paving practices and procedures with only minor modifications to account for the reduction in temperature. The evaluated technologies affected mixture properties in slightly different ways such as changes in tensile strength ratios and variability in air voids. Additional monitoring of constructed sections was recommended to evaluate long-term performance. Inclusion of WMA technology as an option for paving operations provides potential benefits to VDOT and the contracting community. Theoretically, these technologies could extend the asphalt paving season into cooler weather, allowing for better optimization of paving resources. The technologies also allow the construction of asphalt pavements at lower temperatures, resulting in reduced cooling time before the pavement is opened to traffic. Lower production temperatures may also increase mixture durability by reducing production aging of the mix. Benefits to contractors may include the ability to increase hauling distances between the plant and project, reduced plant emissions resulting in improved air quality, and cost savings because of reduced energy costs. Because of the experimental nature of this study, no cost savings data are yet available to justify or refute the use of WMA technologies.
Author: Stacey D. Diefenderfer Publisher: ISBN: Category : Pavements, Asphalt Languages : en Pages : 44
Book Description
Several processes have been developed to reduce the mixing and compaction temperatures of hot mix asphalt (HMA) without sacrificing the quality of the resulting pavement. The purpose of this study was to evaluate the installation of warm mix asphalt (WMA) to compile experiences and offer recommendations for future use. Three trial sections were installed using warm mix technologies between August and November of 2006. Two used the Sasobit technology, and the third employed the Evotherm technology. This report discusses the material makeup of these technologies and documents the production and placement of the three trial sections. The results of this study and further studies can serve as a basis for decision making by the Virginia Department of Transportation (VDOT) regarding the use of WMA technology. Trial sections were initiated through cooperative efforts by the Virginia Transportation Research Council; VDOT districts, residencies, and area headquarters; and participating contractors. Construction used typical mixture designs and practices so that performance under typical construction conditions could be evaluated. General experiences and processes used during construction were documented, and samples were taken for laboratory characterization. Density measurements and cores were taken at each site to determine the initial pavement properties. At the Evotherm installation, asphalt fume sampling was conducted by VDOT's Employee Safety & Health Division to evaluate differences in worker exposure between HMA and WMA pavement laydown operations. The study showed that WMA can be successfully placed using conventional HMA paving practices and procedures with only minor modifications to account for the reduction in temperature. The evaluated technologies affected mixture properties in slightly different ways such as changes in tensile strength ratios and variability in air voids. Additional monitoring of constructed sections was recommended to evaluate long-term performance. Inclusion of WMA technology as an option for paving operations provides potential benefits to VDOT and the contracting community. Theoretically, these technologies could extend the asphalt paving season into cooler weather, allowing for better optimization of paving resources. The technologies also allow the construction of asphalt pavements at lower temperatures, resulting in reduced cooling time before the pavement is opened to traffic. Lower production temperatures may also increase mixture durability by reducing production aging of the mix. Benefits to contractors may include the ability to increase hauling distances between the plant and project, reduced plant emissions resulting in improved air quality, and cost savings because of reduced energy costs. Because of the experimental nature of this study, no cost savings data are yet available to justify or refute the use of WMA technologies.
Author: Stacey D. Diefenderfer Publisher: ISBN: Category : Asphalt concrete Languages : en Pages : 27
Book Description
The Virginia Department of Transportation (VDOT) began allowing the use of warm mix asphalt (WMA) in 2008 and has become a national leader in the use of WMA technologies. Several WMA technologies were investigated in research projects prior to implementation; however, foamed WMA was not. This study was designed to evaluate the properties and performance of foamed WMA placed during the initial implementation of the technology to determine if the technology has performed as expected. Six mixtures produced using plant foaming technologies and placed between 2008 and 2010 were identified and subjected to field coring and laboratory testing to provide insight as to the performance of foamed WMA mixtures. All coring was performed in 2014, which resulted in pavement ages ranging from 4 to 6 years. Three comparable hot mix asphalt (HMA) mixtures were cored and evaluated to provide average values for comparison. All cores were tested to determine air-void contents and permeability and were subjected to dynamic modulus, repeated load permanent deformation, and Texas overlay testing. In addition, binder was extracted and recovered for performance grading. Test results found similar properties for the WMA and HMA mixtures evaluated. One WMA mixture exhibited high dynamic modulus and binder stiffness, but overlay testing did not indicate any tendency toward premature cracking. All binders were found to have aged between two and three performance grades above that which was specified at construction. WMA binders and one HMA binder aged two grades higher, and the remaining two HMA binders aged three grades, indicating a likely influence on aging from the reduced temperatures at which the early foamed mixtures were typically produced. Overall results indicated that foamed WMA should be expected to perform similarly to HMA. WMA has been fully adopted by VDOT as an alternative to HMA since 2008; however, at the time of implementation of foamed WMA, no studies had been conducted by VDOT to assess the performance of WMA relative to that of HMA. This study validated the assumption that the properties and performance of foamed WMA are similar to those of HMA.
Author: Stacey D. Diefenderfer Publisher: ISBN: Category : Pavements, Asphalt Languages : en Pages : 0
Book Description
Three trial sections using two warm-mix asphalt (WMA) technologies were constructed in various locations in Virginia in 2006, and experiences with these trial sections were used in the development of the Virginia Department of Transportation's special provision to allow the use of WMA. WMA for two of the sections was produced using Sasobit, an organic additive (developed by Sasol Wax), and WMA for the third section was produced using Evotherm ET (developed by MeadWestvaco Asphalt Innovations) as the modification method. The sections were evaluated over a 2-year period to assess the initial performance of the WMA and compare it with that of hot-mix asphalt (HMA) control sections constructed at the same time. Coring and visual inspections were performed during the initial construction and at intervals of 3 months, 6 months, 1 year, and 2 years. The cores were tested to determine air-void contents and permeability prior to undergoing extraction and recovery of the asphalt binder for performance grading. In addition, for the two Sasobit trial sites, historic data, core data, and ground-penetrating radar scans were collected and compared to provide documentation of the pavement structure for future analysis. Visual surveys indicated no significant distresses in either the WMA or HMA sections during the first 2 years in service. Evaluations of the core air-void contents indicated that generally the contents for the WMA and HMA were not significantly different in each trial. The air-void contents at different ages were significantly different in a few instances; however, no trends concerning air voids were observed. Permeability measurements did not indicate any trends concerning permeability over time. Performance grading of the recovered binder suggested that the WMA produced using Sasobit aged at a slightly reduced rate than the HMA, as indicated by decreased stiffening. No difference in performance grade was measured between the HMA and WMA produced using the Evotherm emulsion. Comparisons of historical data, core data, and ground-penetrating radar scans illustrated that each may indicate a slightly different pavement structure. From the results of this 2-year investigation, in general, WMA and HMA should be expected to perform equally. Any instances of improved performance of WMA (as compared to HMA) will depend on the WMA technology employed. Some WMA technologies may contribute to reduced in-service binder aging, depending on production temperatures and the nature of the technology. Further evaluation of WMA technologies developed since the inception of this work is recommended to determine their potential for leading to improved performance. During the period from February through October 2009, VDOT let maintenance contracts using HMA surface mixtures valued at approximately $101 million. If, conservatively, one-tenth of these mixtures were replaced with WMA produced using technologies having beneficial aging characteristics and the apparent trend of a 1-year reduction in the rate of aging continued, resulting in a 1-year deferment of repaving, VDOT could realize a one-time cost savings of approximately $1.15 million.
Author: Rajib B. Mallick Publisher: CRC Press ISBN: 1000812553 Category : Technology & Engineering Languages : en Pages : 819
Book Description
Pavement Engineering: Principles and Practice examines a wide range of topics in asphalt and concrete pavements from soil preparation and structural design to life cycle costing and economic analysis. This updated Fourth Edition covers all concepts and practices of pavement engineering in terms of materials, design, and construction methods for both flexible and rigid pavements and includes the latest developments in recycling, sustainable pavement materials, and resilient infrastructure. New and updated topics include material characterization concepts and tests, pavement management concepts, probabilistic examples of life cycle cost analysis, end-of-life considerations, waste plastic in asphalt, pervious concrete, pavement monitoring instrumentation and data acquisition, and more. The latest updated references, state of the art reviews, and online resources have also been included.
Author: Stacey D. Diefenderfer Publisher: ISBN: Category : Pavements, Asphalt--Design and construction Languages : en Pages : 53
Book Description
VDOTs initial warm mix asphalt (WMA) trials were constructed in 2006 and assessed the Sasobit additive and Evotherm DAT technology as compared to a control hot mix asphalt (HMA). The overlays on the sites have been assessed at regular intervals over the course of their lifespan, offering an opportunity to evaluate the long-term performance of these mixtures. This study evaluated the performance of these trial sections over 10 years. During the testing performed as part of this study, cores were taken after 3 months, 6 months, 1 year, 2 years, 5 years, and 10 years of service to determine the rate of densification under traffic and to evaluate changes in the performance of the mixtures over time; in addition, binder was recovered from the cores and graded to evaluate the progression of aging. Pavement management data were also collected annually and evaluated for two of the three sites to determine the relative performance of the HMA and WMA sections. HMA and WMA core air voids were generally similar. Permeability was related to air-void content and appeared to decrease over time. Dynamic modulus results were shown to be mixture dependent, with each mixture showing the effects of aging in a unique manner. Overlay test results indicated no significant differences between the HMA and WMA pairs; however, for two of the three site pairs, this was affected by the test variability. The flexibility index (FI) indicated no significant differences between the HMA and WMA pairs from two sites. The HMA cores from one site showed a significantly higher FI than the WMA cores; however, the WMA core results were similar to the results from the other two sites. Binder testing showed a clear stiffening effect with age for all binders. Evaluation of the Tc cracking parameter indicated that all binders except one HMA binder had exceeded the cracking limit of -5.0 degrees C by 10 years of service, indicating a potential need for remediation to prevent cracking. Data extracted from VDOTs Pavement Management System for two of the sections generally indicated that the HMA and WMA mixtures performed similarly. Although individual distress quantities varied over time, the critical condition index, load related distress index, and non-load related distress index values for each HMA-WMA pair were similar after 10 years of service. Comparison of FI values and overlay test cycles to failure for the 10-year-old cores with deterioration values from the Pavement Management System indicated high correlations in many instances however, the direction of the correlation was counterintuitive in many cases. These results are limited by the very small dataset evaluated. Results of the investigation verified that the HMA and WMA mixtures performed similarly over 10 years of service. It was found that binder aging is causing a significant change in binder properties in service for both HMA and WMA that may affect mixture performance. In addition, relationships between performance-based properties of mixtures and in-service pavement performance were found to be promising, but they need further evaluation.
Author: Charles S. Hughes Publisher: ISBN: Category : Asphalt concrete Languages : en Pages : 64
Book Description
In 2000, the Virginia Department of Transportation's (VDOT) Chief Engineer asked the Virginia Transportation Research Council to develop a vision of how and when VDOT would have a working end-result specification for hot-mix asphalt. The response to that question was that it would take several years and many steps to achieve. This report discusses the next step in that ongoing effort, which includes the development and simulated application of two statistical quality assurance (SQA) special provisions, one for asphalt concrete material and the other for asphalt concrete pavement. The criteria for these prototype SQA provisions included the application of standard national terminology and approach, a firm basis in existing VDOT specifications, and quality characteristics that represent the best practical performance measures. This report describes the outcome of a "shadow" application of the proposed SQA specifications to a subset of Virginia's annual maintenance-resurfacing projects. Although the involved production and placement activities were not subject to the requirements of the SQA specifications, the sampling and testing were designed to represent what would have been required had the special provisions been in effect. The study further determined the likely acceptance outcome for each shadow project and explored future modifications to specification limits and pay adjustment criteria. The most desirable benefit from effective end-result specifications stems from the ability to rededicate available inspection to those key production and placement processes (e.g., joint tacking and surface preparation) that cannot be measured upon delivery to the owner/agency. A less desirable, but more tangible, financial benefit results when these specifications permit a reduction in the overall inspection force. One conservative estimate suggests that VDOT could save more than $2 million per year in inspector salaries through an end-result specification for acceptance of hot-mix asphalt pavements
Author: Stacey D. Diefenderfer
Author: Stacey D. Diefenderfer
Author: Stacey D. Diefenderfer
Author: Stacey D. Diefenderfer
Author: Stacey D. Diefenderfer
Author: Eugene L. Skok
Author: 
Author: Rajib B. Mallick
Author: Stacey D. Diefenderfer
Author: Asphalt Institute
Author: Charles S. Hughes