› › Performance Of Foamed Warm Mix Asphalt In Virginia Over Four To Six Years

Performance of Foamed Warm Mix Asphalt In Virginia Over Four to Six Years

Author : Stacey D. Diefenderfer

Publisher :

Page : 27 pages

File Size : 40,95 MB

Release : 2017

Category : Asphalt concrete

ISBN :

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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.



Properties of Foamed Asphalt for Warm Mix Asphalt Applications

Author : David E. Newcomb

Publisher :

Page : 122 pages

File Size : 37,19 MB

Release : 2015

Category : Asphalt concrete

ISBN : 9780309308663

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Book Description

"TRB's National Cooperative Highway Research Program (NCHRP) Report 807: Properties of Foamed Asphalt for Warm Mix Asphalt Applications presents methods for measuring the performance-related properties of foamed asphalts and designing foamed asphalt mixes with satisfactory aggregate coating and workability." --



Installation of Warm Mix Asphalt Projects in Virginia

Author : Stacey D. Diefenderfer

Publisher :

Page : 44 pages

File Size : 35,39 MB

Release : 2007

Category : Pavements, Asphalt

ISBN :

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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.



Ten-Year Assessment of Virginia's First Warm Mix Asphalt Sites

Author : Stacey D. Diefenderfer

Publisher :

Page : 53 pages

File Size : 48,19 MB

Release : 2019

Category : Pavements, Asphalt--Design and construction

ISBN :

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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.



Performance Evaluation of Foamed Warm Mix Asphalt Produced by Water Injection

Author : Ayman Ali

Publisher :

Page : 201 pages

File Size : 37,47 MB

Release : 2013

Category : Asphalt

ISBN :

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Book Description

In recent years, a new group of technologies has been introduced in the United States that allow producing asphalt mixtures at temperatures 30 to 100oF lower than what is used in traditional hot mix asphalt (HMA). These technologies are commonly referred to as Warm Mix Asphalt (WMA). From among these technologies, foamed WMA produced by water injection has gained increased attention from the asphalt paving industry in Ohio since it does not require the use of costly additives. This type of asphalt mixtures is advertised as an environmentally friendly alternative to traditional HMA and promoted to have better workability and compactability. In spite of these advantages, several concerns have been raised regarding the performance of foamed WMA because of the reduced production temperature and its impact on aggregate drying and asphalt binder aging. Main concerns include increased propensity for moisture-induced damage (durability) and increased susceptibility to permanent deformation (rutting). Other concerns include insufficient coating of coarse aggregates, and applicability of HMA mix design procedures to foamed WMA mixtures. This dissertation presents the results of a comprehensive study conducted to evaluate the laboratory performance of foamed WMA mixtures with regard to permanent deformation, moisture-induced damage, fatigue cracking, and low-temperature (thermal) cracking; and compare it to traditional HMA. In addition, the workability of foamed WMA and HMA mixtures was evaluated using a new device that was designed and fabricated at the University of Akron, and the compactability of both mixtures was examined by analyzing compaction data collected using the Superpave gyratory compactor. The effect of the temperature reduction, foaming water content, and aggregate moisture content on the performance of foamed WMA was also investigated. Furthermore, the rutting performance of plant-produced foamed WMA and HMA mixtures was evaluated in the Accelerated Pavement Load Facility (APLF) at Ohio University, and the long-term performance of pavement structures constructed using foamed WMA and HMA surface and intermediate courses was analyzed using the Mechanistic-Empirical Pavement Design Guide (MEPDG). Based on the experimental test results and the subsequent analyses findings, the following are the main conclusions made: In general, comparable laboratory test results were obtained for foamed WMA and HMA mixtures prepared using 30°F (16.7°C) temperature reduction, 1.8% foaming water content, and fully dried aggregates. Therefore, the performance of the resulting foamed WMA is expected to be similar to that of the HMA. Surface foamed WMA mixtures had comparable rutting performance in the APLF to that of the HMA mixtures. This was also the case for intermediate foamed WMA and HMA mixtures. These results indicate the field performance of the foamed WMA mixtures is similar to that of the HMA mixtures.



Low Temperature Characterization of Foamed Warm Mix Asphalt

Author : Ahmad Alhasan

Publisher :

Page : 112 pages

File Size : 14,94 MB

Release : 2013

Category : Asphalt

ISBN :

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Book Description

In recent years, a group of technologies has been introduced in the United States that allows producing asphalt mixtures at temperatures 30 to 100oF lower than what is used in traditional hot mix asphalt (HMA). This group of technologies is commonly referred to as Warm Mix Asphalt (WMA). From among these technologies, foamed WMA produced by water injection has gained increased attention from the asphalt paving industry in Ohio since it does not require the use of costly additives. This study evaluated the low-temperature performance of foamed WMA and compared it to traditional HMA. Two asphalt binders (PG 70-22 and PG 64-28), two aggregate types (limestone and crushed gravel), and two aggregate gradations (12.5 mm NMAS and 19.0 mm NMAS) were used in this study. The low-temperature behavior of the asphalt mixtures was evaluated using the thermal stress restrained specimen test (TSRST). In addition, the low-temperature properties of the asphalt binders were measured using the bending beam rheometer (BBR). This allowed for comparing the fracture temperature obtained from the TSRST to the low-temperature performance grade obtained using the BBR test.In general, the foamed WMA mixtures exhibited warmer fracture temperatures and lower fracture stresses in the TSRST than the traditional HMA mixtures. This indicates that the HMA mixtures have better resistance to low-temperature cracking. It was found that the binder grade had the most significant effect on the fracture temperature followed by the mix type, while the aggregate type had the most significant effect on the fracture stress followed by the binder grade and the mix type. The fracture temperatures measured in the TSRST were also found to be consistent with the low-temperature performance grades obtained using the BBR test.





Influence of Aging on Foamed Warm Mix Asphalt

Author : Sunday Akinbowale

Publisher :

Page : 0 pages

File Size : 20,82 MB

Release : 2014

Category : Asphalt

ISBN :

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Book Description

Over the years, the use of warm mix in pavement structures has continued to gain increasing attention in United States because of its implicit advantages over the traditional hot mix. This has necessitated increased research efforts into understanding different aspects of its behaviour and performance. Aging of asphalt is particularly of much importance because it leads to several problems such as pavement rutting, fatigue cracking and thermal cracking. The aging that occurs during mixing and compaction is commonly referred to as short term aging while the aging that occurs during the pavement service life is called long term aging. The main reason for aging in binders is oxidation and binders become stiffer due to oxidation. Several research projects have been carried out on investigating the aging behavior of warm mix asphalt (WMA) produced by different chemical additives. But no major study has been conducted to understand the aging behavior of foamed WMA. Therefore, this study characterizes the aging behavior of foamed (WMA) as it compares to the traditional hot mix asphalt (HMA) using the Dynamic Shear Rheometer (DSR), Fourier Transforms Infrared Spectroscopy (FTIR), and Gel Permeation Chromatography (GPC) tests. Investigation of the effect of extraction and recovery with trichloroethylene on the stiffness of binders was initially carried out. In addition to preparation of mixtures, aging of binders (RTFO and PAV) and aging of mixtures (STOA and LTOA) being simulated in the laboratory using PG 70-22M and PG 64-22 binder grades, field cores were also obtained from test sections which had been in service for five years. Binders were extracted and recovered from both laboratory and field samples for subsequent physical and chemical tests. These results were analysed and used to evaluate the aging behavior of foamed WMA as it compares to HMA. It was observed that extraction and recovery procedure with trichloroethylene had minimal effect on PG 70-22M binders while it had a reductive effect on rutting and fatigue parameter values of PG 64-22 binders at different levels of aging. Both foamed WMA and HMA for PG 70-22M responded similarly to field and laboratory-simulated aging conditions. But for PG 64-22 binders, foamed WMA was found to be less susceptible to aging than the traditional HMA. Therefore, it implies that when the foamed warm mix technology is used, it may be expected to have a better performance in fatigue cracking but more susceptible to rutting or permanent deformation that takes place in pavement early years when compared to the traditional Hot Mix Asphalt.



Warm Mix Asphalt

Author : Paula Cristina Arroyo-Martínez

Publisher :

Page : 0 pages

File Size : 11,30 MB

Release : 2019

Category : Electronic books

ISBN :

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Book Description

Warm mix asphalt (WMA) is a technology that emerges to achieve environmental challenges of reducing greenhouse gas emissions. There are several technologies that allow diminishing the mixing and compaction temperature of the asphalt mixtures while improving workability. The benefits of using warm mix asphalt are not just environmental but also include better working conditions and the capability of introducing greater percentages of recycled materials into the mixture. Foamed asphalt is the most used technology to obtained warm mix asphalt in the United States of America (USA), and the performance of the resultant mixtures could be increased by controlling and improving the characteristics of the foam.