Evaluation of Hybrid Rubber Modified Asphalt Mixtures and Pavements: A Case Study in Virginia
Evaluation of Hybrid Rubber Modified Asphalt Mixtures and Pavements: A Case Study in Virginia

Author: Jhony Habbouche

Publisher:

Published: 2023

Total Pages: 0

ISBN-13:

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Several state departments of transportation have recognized the benefits of modified asphalt mixtures in resisting multiple modes of climate- and load-induced distresses in flexible pavements. Throughout the past 50 years, asphalt binders have been modified with various components such as styrene-butadiene-styrene (SBS) polymers, ground tire rubber, chemicals (e.g., acid), recycled engine oils, etc., to achieve the desired properties. Hybrid rubber modified asphalt (HRMA) is an innovative engineered additive derived from ground tire rubber, elastomeric SBS polymers, and additive technologies. HRMA is specifically formulated to improve the high temperature stiffness and elastic properties of performance graded binders and the storage stability of modified binders. The purpose of this study was to document and assess HRMA field trials constructed in Virginia. This study documented and evaluated the constructability and laboratory performance of two plant-produced HRMA mixtures compared with the Virginia Department of Transportation (VDOT) typical SBS-modified surface mixtures as reference mixtures. No changes from routine established practices in terms of surface preparation, production at the plant, or paving operations were reported. The four mixtures were evaluated in terms of durability, dynamic modulus, resistance to rutting, and resistance to cracking using multi-level performance tests (basic, intermediate, advanced). All the derived observations indicated that HRMA modification could be as beneficial as regular SBS modification and could provide similar or better performance properties and characteristics for the resultant mixtures. The study recommends that VDOT consider the use of HRMA surface mixtures as an alternative to the current use of regular SBS-modified surface mixtures on higher-volume facilities. Since the sections evaluated in this study were placed in 2021, the 2-year performance data and corresponding observations are still considered preliminary. Continued monitoring of field performance will be needed to quantify any benefit of HRMA mixtures in comparison with regular SBS-modified surface mixtures. The study also recommends additional field trials with HRMA mixtures for further performance evaluation.

Rubber Modified Asphalt Mix
Rubber Modified Asphalt Mix

Author: Charles S. Hughes

Publisher:

Published: 1985

Total Pages: 16

ISBN-13:

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This report summarizes the design and field installation of an asphalt mix containing up to 3.0% closed cell rubber by weight of the mix. The performance is discussed as well as possible reasons for the early failure of the mix. Suggestions are made for avoiding failures if it is decided to use rubber modified mixes in the future.

Performance of Ground Tire Rubber Modified Asphalt Mixture Overlays Over Jointed Concrete Pavements on US 60 in the Virginia Department of Transportation’s Richmond District
Performance of Ground Tire Rubber Modified Asphalt Mixture Overlays Over Jointed Concrete Pavements on US 60 in the Virginia Department of Transportation’s Richmond District

Author: Harikrishnan Nair

Publisher:

Published: 2022

Total Pages: 0

ISBN-13:

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Ground tire rubber (GTR) from scrap tires is used in asphalt mixtures (rubber modified asphalt [RMA]) for improving the performance of pavements. There are different ways to add GTR in asphalt mixtures, but the two primary methods are referred to as the “wet” and “dry” processes. The dry process incorporates GTR directly into the asphalt mixture during production (directly to the aggregates through the reclaimed asphalt pavement collar). The Virginia Department of Transportation (VDOT) has limited experience with RMA mixtures in Superpave dense-graded mixtures using the dry process, but the relative ease of mixture production makes the dry process an attractive option for RMA. In the fall of 2019, VDOT placed a dense-graded RMA mixture, SM 12.5 (GTR), on US 60 in VDOT’s Richmond District (New Kent County). This was the first use of a SM 12.5 (GTR) mixture in Virginia using the dry process method. The purpose of this study was to establish a performance baseline for a GTR modified dense-graded asphalt mixture that was designed and produced using the dry process. The US 60 project also included the use of a thin hot mix asphalt concrete overlay (THMACO) as an interlayer. An assessment of the THMACO as an interlayer was a secondary objective of the study. The study found that dry process SM 12.5 (GTR) mixture can be produced and placed with no significant field-related concerns and that the special provision developed for its use was effective. Density requirements were achieved, and the as-placed mat had excellent (very low) permeability characteristics. Laboratory performance testing showed the SM 12.5 (GTR) mixture to be more crack resistant than conventionally modified polymer (SM 12.5E) mixtures. Conventionally modified SM E mixtures had slightly better rutting performance. However, this conclusion was based on performance testing and thresholds that were developed for non-modified asphalt mixtures. Additional laboratory and field performance comparison is needed to develop mixture acceptance criteria for GTR mixtures. Further, THMACO mixtures had excellent laboratory reflective cracking resistance properties. They performed particularly well in the Texas overlay test. Grading of extracted (from the asphalt mixture) binder may not provide an accurate representation of the binder performance for the dry process GTR modified asphalt. Continued monitoring of performance will be needed to quantify any benefit of SM 12.5 (GFR) mixtures in comparison with regular SM E mixtures. The study recommends additional field trials with SM 12.5 (GTR) mixtures for performance evaluation. Further, the study recommends continued use of a THMACO as an interlayer to mitigate reflective cracking for composite pavements.

Evaluation of Mix Ingredients on the Performance of Rubber-modified Asphalt Mixtures
Evaluation of Mix Ingredients on the Performance of Rubber-modified Asphalt Mixtures

Author: Hossein B. Takallou

Publisher:

Published: 1987

Total Pages: 694

ISBN-13:

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Rubber-modified asphalt pavements have been used in Sweden and the United States since the 1970's. In these applications ground recycled tire particles (1/4 inch minus) are added to a gap-graded aggregate and then mixed with hot asphalt cement. The benefits of adding rubber to the mix include increased skid resistance under icy conditions, improved flexibility and crack resistance, elimination of solid waste, and reduced traffic noise. The major disadvantage of these rubber-modified mixes is their high cost in relation to conventional asphaltic concrete pavements. This research project consisted of a laboratory study of mix properties as a function of variables such as rubber gradation and content, void content, aggregate gradation, mix process, temperature, and asphalt content. Twenty different mix combinations were evaluated for diametral modulus and fatigue at two different temperatures ( -6°C, +10°C). Also, five different mix combinations were evaluated for static creep and permanent deformation. Layered theory was used to evaluate the effects of mixture variations on pavement life. The resulting information was used to develop guidelines for use of rubber asphalt mixes in United States road systems. The findings of the field survey indicate that the rubber-modified asphalt mixture is more susceptible than the conventional mixtures to preparation and compaction problems when adverse weather or equipment problems occur. However, with adequate equipment and favorable weather conditions, the rubber-modified asphalt mixture placement is similar to conventional mixture placement. The field study also indicates that stopping distances can be reduced 20 percent for the rubber-modified pavements in icy conditions. In view of the significant reductions in wintertime stopping distances under icy or frosty road surface conditions, the use of coarse rubber in asphalt pavements should be seriously considered. This is particularly true for areas such as bridge decks, on and off freeway ramps or insulated roadway sections. The findings of the laboratory study indicate that the rubber gradation and content, aggregate gradation, and use of surcharge during sample preparation have considerable effect on modulus and fatigue life of the mix. The results of static creep and permanent deformation tests indicate that the rubber asphalt mixes had low stability and high elasticity. Also, due to greater allowable tensile strain in rubber-modified mixtures, the thickness of the modified mixture can be reduced, using a layer equivalency of 1.4 to 1.0.

Installation Report
Installation Report

Author: Charles S. Hughes

Publisher:

Published: 1983

Total Pages: 11

ISBN-13:

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This report describes the design of an asphalt mix containing up to 3.0% closed cell waste rubber and a field installation of the mix. The Marshall design procedure was used to determine the asphalt content for the mix containing 3.0% rubber as well as that of a control mix which did not contain rubber. In the field installation, 211 tons of mix containing 1.5% or 3.0% rubber were laid on Route 460 in Bedford County. The only problem encountered was that the breakdown roller tended to pick up the mix until the temperature decreased to 225°F. Results of Marshall tests made on samples taken from the field mix are presented in the report.

Evaluation of a Modified Asphalt
Evaluation of a Modified Asphalt

Author: G. W. Maupin

Publisher:

Published: 1993

Total Pages: 30

ISBN-13:

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Because of increased traffic loads and truck tire pressures over the last few years, the rutting of asphalt pavements has worsened. Additives such as polymers are being used in an attempt to improve the performance of these pavements. One such product is Novophalt, which is the registered trademark of an asphalt modified with 4 to 6 percent of a polyolefin polymer, primarily polyethylene. A Novophalt surface mixture was used near an intersection on a new construction project to guard against rutting caused by heavy trucks. This study evaluated the construction and performance of sections of pavement with control and Novophalt mixtures at this location. The polymer-modified mixture was manufactured, placed, and compacted with no difficulty. Severe ruts developed in both the control and Novophalt sections under stopped traffic near the traffic light. The rutting was found to be caused by a weak base mixture under the Novophalt surface; the rutting under the control mixture was probably also related to the base mixture. No significant rutting occurred in the control and Novophalt sections in the areas not subjected to severe traffic loads. Although the comparison between the control and Novophalt mixtures was vitiated by the performance of the underlying base mixture, the project demonstrated that construction with the Novophalt mixture could be accomplished satisfactorily.

Evaluation of Highly Polymer-Modified Asphalt Mixtures: Phase I
Evaluation of Highly Polymer-Modified Asphalt Mixtures: Phase I

Author: Benjamin F. Bowers

Publisher:

Published: 2018

Total Pages: 0

ISBN-13:

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Reflective cracking in asphalt overlays placed over jointed concrete pavement has been a concern of the Virginia Department of Transportation (VDOT) for years. Although there are many techniques to delay crack propagation through an asphalt overlay, they may require specialized equipment, unique mix designs, or other specific mixture additives. The introduction of highly polymer-modified (HP) binders to the market brings forward a new potential crack mitigation method requiring only the use of the HP binder in an asphalt mixture to provide mitigation. Before asphalt mixtures with HP binder were used on a jointed concrete overlay project, a trial project to evaluate the constructability and laboratory performance of a mixture using this type of binder was conducted. The trial project compared an asphalt surface mixture with an HP binder and a standard surface mixture (control) in a mill and resurfacing pavement project in a subdivision in Northern Virginia. The asphalt surface mixture with the HP binder was found to be constructible without major changes in paving operations; in addition, the laboratory performance was equivalent or superior to that of the control mixture. The results were promising enough to support investigating the use of HP binders in asphalt mixtures over jointed concrete as a reflective crack mitigation technique or when deemed appropriate as a tool for increased crack resistance. The study recommends that VDOT consider the use of asphalt mixtures with HP binders as a tool for increased crack resistance when deemed appropriate by the appropriate VDOT decision maker (e.g., the district materials engineer). The study also recommends that the Virginia Transportation Research Council and the VDOT districts with concerns about reflective cracking potential in asphalt overlays investigate the use of HP mixtures as a reflective crack mitigation layer.

Effect of Mix Ingredients on Performance of Rubber Modified Asphalt Mixtures
Effect of Mix Ingredients on Performance of Rubber Modified Asphalt Mixtures

Author: H. B. Takallou

Publisher:

Published: 1985

Total Pages: 160

ISBN-13:

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This report summarizes the results of field performance surveys and laboratory testing programs aimed at identifying the critical factors in designing and constructing rubber-modified asphalt pavements using a content of 2 to 3% of coarse (1/4 inch to #40 sieve) ground tire rubber. The benefits of adding rubber in this size range to asphalt paving mixes are those of increasing traction and reducing stopping distances.

Evaluation of Warm Mix Additives for Use in Modified Asphalt Mixtures
Evaluation of Warm Mix Additives for Use in Modified Asphalt Mixtures

Author: Rukesh Maharjan

Publisher:

Published: 2015

Total Pages: 332

ISBN-13:

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The purpose of this research effort was to evaluate the use of warm-mix additives with modified (polymer-modified and terminal blend tire rubber) asphalt mixtures from Nevada and California. This research was completed in two stages: Sasobit and Advera were evaluated in first stage while Evotherm and Foaming were evaluated in second stage. The three main components of the experimental plan include: evaluation of mixture resistivity to moisture damage, pavement performance characteristics of the mixtures, and mechanistic analysis of the mixtures for simulated flexible pavement. The moisture resistivity of all mixtures were checked by Indirect Tensile Strength (ITS), and Dynamic Modulus (E*) tests. Dynamic Modulus Ratio (ECR) and Tensile Strength Ratio (TSR) were computed at multiple Freeze-Thaw (F-T) cycles for further evaluation of moisture sensitivity of mixtures. Flow Number (FN) and Flexural beam fatigue tests were conducted to evaluate the performance characteristics of WMA additives/technology. The terminal blend tire rubber-modified binder with lime treatment works effectively in resisting moisture damage, rutting, and to significantly-reasonably improve the fatigue life of the WMA Evotherm, Foaming, Advera and Sasobit mixtures. Hence, it is the best solution for the design and construction of sustainable asphalt pavements. The use of terminal blend rubberized asphalt binder is an excellent and economical selection in reducing tire waste and environmental impacts.