Education

Research Description

Dr. Castorena's research is focused on characterization of asphalt materials. Specifically, her work utilizes multi-scale characterization to develop a fundamental understanding of asphalt binders and their interaction with mineral aggregates. This work aims to improve our methods for asphalt pavement material selection and design. Additionally, she investigates the use of innovative alternative cement binders and asphalt modification technology for improved pavement sustainability.

Publications

Assessment of the impacts of sample preparation on the use of EDS for analysing recycled asphalt blending

Pape, S. E., & Castorena, C. A. (2021, June 17), JOURNAL OF MICROSCOPY, Vol. 6. https://doi.org/10.1111/jmi.13036

COVID-19, Uncertainty, and the Need for Resilience-Based Thinking in Pavement Engineering

Gulzar, S., Richard Kim, Y., Castorena, C., & Shane Underwood, B. (2021), JOURNAL OF TRANSPORTATION ENGINEERING PART B-PAVEMENTS, 3. https://doi.org/10.1061/JPEODX.0000235

Critical Evaluation of Dynamic Shear Rheometer (DSR)-Based Methods to Measure Asphalt Binder Diffusion

Ravichandran, M., & Castorena, C. (2021), JOURNAL OF TESTING AND EVALUATION, 11. https://doi.org/10.1520/JTE20200432

Refinement of Climate-, Depth-, and Time-Based Laboratory Aging Procedure for Asphalt Mixtures

Braswell, E., Saleh, N. F., Elwardany, M., Yousefi Rad, F., Castorena, C., Underwood, B. S., & Kim, Y. R. (2021), TRANSPORTATION RESEARCH RECORD, 2675(2), 207–218. https://doi.org/10.1177/0361198120957316

Review From Multiple Perspectives for the State of the Practice on the Use of Recycled Asphalt Materials and Recycling Agents in Asphalt Concrete Surface Mixtures

Habbouche, J., Boz, I., Underwood, B. S., Castorena, C., Gulzar, S., Fried, A., & Preciado, J. (2021, December 9), TRANSPORTATION RESEARCH RECORD, Vol. 12. https://doi.org/10.1177/03611981211061130

Use of Resampling Method to Construct Variance Index and Repeatability Limit of Damage Characteristic Curve

Ding, J., Lee, K. C., Castorena, C., Kim, Y. R., & Underwood, B. S. (2021, February 22), TRANSPORTATION RESEARCH RECORD, Vol. 2. https://doi.org/10.1177/0361198121994850

Effects of aging on asphalt mixture and pavement performance

Saleh, N. F., Keshavarzi, B., Rad, F. Y., Mocelin, D., Elwardany, M., Castorena, C., … Kim, Y. R. (2020), CONSTRUCTION AND BUILDING MATERIALS, 258. https://doi.org/10.1016/j.conbuildmat.2020.120309

Improved interpretation of asphalt binder parallel plate dynamic shear rheometer fatigue tests

Safaei, F., & Castorena, C. (2020), INTERNATIONAL JOURNAL OF PAVEMENT ENGINEERING, 21(1), 74–87. https://doi.org/10.1080/10298436.2018.1438611

Low-temperature performance grade characterisation of asphalt binder using the dynamic shear rheometer

Zeng, Z. 'A., Underwood, B. S., & Castorena, C. (2020), INTERNATIONAL JOURNAL OF PAVEMENT ENGINEERING. https://doi.org/10.1080/10298436.2020.1774766

Predictive Framework for Modeling Changes in Asphalt Mixture Moduli with Oxidative Aging

Saleh, N. F., Mocelin, D., Yousefi Rad, F., Castorena, C., Underwood, B. S., & Kim, Y. R. (2020), TRANSPORTATION RESEARCH RECORD. https://doi.org/10.1177/0361198120938775

View all publications via NC State Libraries

Grants

Development of Friction Performance Models

NC Department of Transportation(8/01/21 - 7/31/23)

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Development of Friction Performance Models

Sponsor: NC Department of Transportation

Start Date: 8/01/21

End Date: 7/31/23

Abstract

Vehicle collisions and increases in collisions rates during wet conditions are one of the major safety concerns for the NCDOT. Collision rates increase when the surface is wet because skid resistance reduces under these conditions. The precise amount of loss is dependent on many factors, but the consensus among experts is that pavement friction and macrotexture are important factors that affect the skid resistance and changes in this resistance under wet conditions. This research will achieve three objectives; 1) characterize friction and texture performance models, 2) develop friction and texture performance thresholds, and 3) identify asphalt mixture compositional factors (gradation, asphalt content, presence of modified versus non-modified asphalt, etc.) that affect the as-constructed macrotexture and friction. The primary outcome of the proposed research will be an initial set of performance models that can be used to assess immediate and potentially long-term friction/macrotexture issues. The research will also produce a set of threshold limits for friction/macrotexture where investigatory and intervention steps need to be taken to control for safety. Finally, the research will produce information on the mixture design factors that contribute to higher or lower friction/macrotexture. These outcomes can be used by the Traffic Safety and Materials and Test Units of the North Carolina DOT to predict and manage friction and texture performance on roadways and to understand when measurements represent a potential hazard exists. It will also be used to help identify asphalt mixtures with potential friction and macrotexture issues and develop better guidelines, specifications, and operational controls (if necessary) for recently overlaid pavements. This could lead to reduced collision rates on these pavements. Thus, this research will result in overall improved procedures for flexible pavement overlay operations.

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A Practical Method to Determine Reclaimed Asphalt Pavement (RAP) Binder Availability

Federal Highway Administration (FHWA)(10/01/21 - 3/31/23)

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A Practical Method to Determine Reclaimed Asphalt Pavement (RAP) Binder Availability

Sponsor: Federal Highway Administration (FHWA)

Start Date: 10/01/21

End Date: 3/31/23

Abstract

This project will explore an innovative method to determine Reclaimed Asphalt Pavement (RAP) binder availability. RAP binder availability refers to the percentage of total RAP binder that is released and available to blend with virgin asphalt during asphalt mixture production. Research has shown that the primary source of unavailable recycled binder is agglomerations of adhered RAP particles. The binder bound within the agglomerations is prohibited from coming contacting and therefore, blending with virgin asphalt. The proposed innovation determines the extent of RAP agglomeration and, in turn, RAP binder availability by comparing the gradation of recovered RAP aggregates to that of the RAP itself. Quantifying the inactive recycled binder content of RAP sources using the proposed innovation offers a means to discredit unavailable recycled binder within design practices. It is expected that discrediting unavailable recycled binder will improve the design and performance of high RAP content mixtures, consequently increasing pavement service life and reducing life cycle costs. The research products may also enable the design of satisfactory asphalt mixtures with higher RAP contents, resulting in environmental and cost benefits. Preliminary results of the proposed innovation are promising. This project will rigorously optimize the innovation, evaluate the performance implications of discrediting inactive recycled binder within design procedures, and develop a provisional AASHTO standard procedure.

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Modifying Existing Asphalt Mix Design Procedures for RAP/RAS Surface Mixtures

NC Department of Transportation(1/01/21 - 12/31/22)

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Modifying Existing Asphalt Mix Design Procedures for RAP/RAS Surface Mixtures

Sponsor: NC Department of Transportation

Start Date: 1/01/21

End Date: 12/31/22

Abstract

The use of high Recycled Binder Replacement Percentages (RBRs%) in asphalt surface mixtures is increasing. The asphalt binders in recycled materials are generally hardened and embrittled from oxidization and may not fully mobilize and blend with virgin materials. Consequently, high recycled content mixtures may be prone to cracking if appropriate measures to consider this effect are not taken during the mixture design process. The objectives of the proposed research project are to: (1) modify the NCDOT’s procedures for the design of surface mixtures containing RAP and RAS to improve performance and (2) modify the NCDOT’s specifications to improve the consistency within and across RAP and RAS stockpiles within North Carolina. 1. To achieve these objectives, an operational review will be conducted to identify how contractors process, stockpile, characterize and use RAP and RAS under the current NCDOT guidelines. In addition, relationships between asphalt content and performance will be developed for recycled mixtures sourced from North Carolina. These relationships will be used to identify the maximum virgin binder content allowable and to maximize cracking performance without having the rutting performance fall below a critical performance threshold for each mixture. The collective results will be used to identify appropriate revisions to the NCDOT’s current recycled mixture design procedure to ensure reliable performance. The research results will lead improved specifications that will facilitate the design of better-performing surface mixtures containing recycled materials. These specifications will improve the durability of NCDOT pavements and consequently decrease life-cycle costs.

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Evaluating Recycling Agents’ Acceptance for Virginia: Test Protocols and Performance-Based Threshold Criteria

US Dept. of Transportation (DOT)(7/01/20 - 1/31/23)

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Evaluating Recycling Agents’ Acceptance for Virginia: Test Protocols and Performance-Based Threshold Criteria

Sponsor: US Dept. of Transportation (DOT)

Start Date: 7/01/20

End Date: 1/31/23

Abstract

In 2007, the Virginia Department of Transportation (VDOT) introduced specifications to allow higher percentages of reclaimed asphalt pavement (RAP) (i.e., up to 30%) in hot-mix asphalt (HMA) surface mixtures without adjustment of the virgin binder grade. The increased use of RAP was expected to result in a lower cost of produced asphalt mixtures given the continuous rising cost of oil and thus asphalt binders and fuel needed to produce asphalt pavements. By 2013, VDOT had begun to consider the feasibility of allowing the use of surface mixtures containing up to 45% of RAP material. Several trial sections were constructed containing mixtures with 20%, 30%, 40%, and 45% RAP for evaluation (Nair et al., 2019). In general, those trials found that mixtures containing up to 45% RAP could be designed, produced, and constructed if proper procedures are followed. In 2019, the research team at Virginia Transportation Research Council (VTRC) initiated another study to evaluate field trials of high RAP asphalt mixtures (i.e., more than 40%) designed following the Balanced Mix Design (BMD) special provision for VDOT’s surface mixtures. The primary concern with such mixtures has been that the use of high percentage of RAP will overly stiffen mixtures; making them more brittle and prone to premature cracking. The use of high percentage of RAP can lead to numerous construction and performance issues including, but not limited to, compactibility and workability in cool weather, low-temperature cracking with accumulation of thermally induced stresses, fatigue cracking and micro damage accumulation leading to crack initiation and propagation with repeated loading, reflection cracking with repeated loading and daily / seasonal thermal stresses, and raveling with subsequent aging or moisture damage. The challenges arising from the use of high RAP content mixtures can be addressed through the use of softer binders or additives such as recycling agents (RAs). These additives were utilized in HMA in the early period of widespread recycling in the 1970s and 1980s for the purpose of realizing three types of benefits: environmental, economic, and engineering. The use of RAs holds promise as long as there is a proper understanding of how effectively they restore binder rheology and how that effectiveness evolves with aging of mixtures in the laboratory, making them proper additives to be incorporated in mixtures to be placed in field. Hence, there is a need for an engineered framework to evaluate RAs in terms of their stiffness and cracking resistance when incorporated into the binder blends of corresponding mixtures. Currently, there are no unique and / or detailed handy guides or specifications that outline a framework to evaluate acceptability of RAs in the state of Virginia. Therefore, this study aims to identify and / or develop a testing protocol to evaluate the effectiveness of RAs in alleviating the brittleness of high RAP asphalt mixtures. In addition, a performance-based parameter(s) with its threshold limits / criteria will be identified or developed to accept or reject a certain product (i.e., recycling agents). Both objectives will facilitate responsible use of innovative materials as part of Virginia’s Balanced Mix Design (BMD) initiative. In this study, NCSU researchers will conduct experiments on asphalt binder, asphalt from reclaimed asphalt pavement (RAP), rejuvenator agents, mortars, and asphalt mixture.

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Ruggedness and Interlaboratory Studies for Asphalt Mixture Performance Tester (AMPT) Small Scale Dynamic Modulus

Federal Highway Administration (FHWA)(3/11/20 - 8/23/22)

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Ruggedness and Interlaboratory Studies for Asphalt Mixture Performance Tester (AMPT) Small Scale Dynamic Modulus

Sponsor: Federal Highway Administration (FHWA)

Start Date: 3/11/20

End Date: 8/23/22

Abstract

In this research study, NCSU will design, conduct, and provide recommendations relating to a two-phase ruggedness and interlaboratory study on a test method that has been identified as critical to asphalt pavement performance and design practice. AASHTO TP 132 (2019) Standard Method of Test for Determining the Dynamic Modulus for Asphalt Mixtures Using Small Specimens in the Asphalt Mixture Performance Tester (AMPT) has been developed, refined, and recently published as an AASHTO provisional standard; a statistically sound refinement procedure is needed to facilitate widespread adoption and implementation. Not only can this standard be used to obtain inputs to the AASHTO PavementME pavement structural analysis software, the standard is being used in ongoing FHWA efforts as part of a performance-related specification framework which seeks to increase pavement life through fundamental testing and predictive relationships. AASHTO TP 132 is of interest because of its fundamental nature, determination via the AMPT standardized equipment, and its ability to model and predict material performance over a wide range of loading and climate conditions a pavement may experience; resulting in better performing, safe, quiet, durable, long lasting asphalt roadways. Additionally, a draft practice for preparing small-scale specimens has been developed and published as AASHTO PP 99 (2019) Standard Method of Practice for Preparation of Small Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor (SGC) and Field Cores. This draft practice is of significant interest to the asphalt materials community due to anticipated materials, time, and cost savings associated with preparing and evaluating smaller performance test. NCSU will carry out the following tasks. Task 1 – Develop final research plans and project schedule – The proposed plan will be revised based on feedback from the FHWA. Task 2 – Kickoff meeting – NCSU will meet with the project panel to review the statement of work and work plans. Task 3 – Perform work plan and document efforts – NCSU will carry out the approved work plan by following the appropriate ASTM standard test methods to develop a rugged test method. Task 4 – Ruggedness study presentations and webinar – NCSU will present the findings to targeted stakeholders. Task 5 – Publication ready final deliverables – the AASHTO standards will be revised into a final form. Task 6 – Revise work ILS work plan – NCSU will revise the original work plan from Task 1 based on findings from Tasks 3-5 for conducting the ILS study. Task 7 – Perform work plan and document efforts – NCSU will coordinate the ILS according to the approved work plan. This will include identifying participants, sending materials, and analyzing their results statistically. Task 8 – ILS study presentation and webinar – NCSU will present their findings to targeted stakeholders. Task 9 – Publication ready final deliverables – the AASHTO standards revised in Task 5 will be modified to include repeatability and reproducibility statements.

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Quality Control of Field Asphalt Mixtures and Compatibility of Aggregates and Emulsions using Asphalt Compatibility Tester (ACT)

NC Department of Transportation(8/01/19 - 4/30/22)

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Quality Control of Field Asphalt Mixtures and Compatibility of Aggregates and Emulsions using Asphalt Compatibility Tester (ACT)

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 4/30/22

Abstract

Asphalt mixtures used in pavement construction are required to meet the North Carolina Department of Transportation (NCDOT) moisture sensitivity specifications. To improve resistance to moisture damage various antistrip additives are used by the asphalt plants producing asphalt mixtures. These antistrip additives help improve the adhesion between asphalt and aggregate and thus improve the resistance of the asphalt mixtures to moisture damage. The antistrip additives are added to the asphalt mixture at the plant by various mechanisms based on the type of antistrip additive being used or they come premixed with the asphalt liquid. The additive is usually added to the asphalt liquid. A problem in the mechanism used to add the antistrip additive to the asphalt might lead to a lesser amount, or no antistrip additive being added into the asphalt mixture. This might lead to the asphalt mixture not meeting the NCDOT moisture sensitivity specifications. Since the additive is added to the asphalt liquid, any problem in the mechanism will not be noticed until the asphalt mixture is tested for its moisture sensitivity.

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Screening of Asphalt Extenders and Recycling Agents

NC Department of Transportation(8/01/19 - 7/31/22)

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Screening of Asphalt Extenders and Recycling Agents

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 7/31/22

Abstract

The use of asphalt mixtures containing high Recycled Binder Replacements (RBRs) is increasing. Recycled binders are oxidized and thus, harder and more susceptible to cracking than virgin binders. Consequently, the use of higher recycled content mixtures has prompted heightened interest in recycling agents and necessitated the use of asphalt extenders to produce softer virgin binder grades. Recycling agents include a wide-range of both softening agents and rejuvenators that are intended to restore the physical and chemical properties of aged asphalt binders. Petroleum-based extender products have been in existence for a long time (e.g., Re-refined Engine Oil Bottom (REOB)). Non-petroleum based products have been more recently introduced (e.g., bio-oils).

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Evolution of Pavement Friction and Macrotexture after Asphalt Overlay

NC Department of Transportation(8/01/19 - 10/31/21)

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Evolution of Pavement Friction and Macrotexture after Asphalt Overlay

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 10/31/21

Abstract

Vehicle collisions and increases in collisions rates during wet conditions are one of the major safety concerns for the NCDOT. Wet collision rates increase because skid resistance reduces under wet conditions. The precise amount of loss is dependent on many factors, but the consensus among experts is that pavement friction and macrotexture are important factors that affect the skid resistance and changes in this resistance under wet conditions. Although the NCDOT actively addresses skid resistance issues as they are identified, a recent study involving a small subset of North Carolina roadways has suggested that wet crash rates may increase after pavements are overlaid. That study concluded that NCDOT needed to consider characterization of both friction and macrotexture as part of its pavement friction measurement and management plan. While the current studies have successfully identified the potential for issues in recently overlaid projects, they did not identify whether these effects are temporary, and if so, how long they may last. In addition, past studies have not been able to identify any specific causative effects that may increase or decrease the impact of overlays on skid resistance. Since the primary change after an overlay is placed is the driving surface, there is a need to better understand how the asphalt mixture composition may affect the overall skid resistance of the roadway under wet conditions.

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Evaluation of New Asphalt Concrete Job Mix Formula Specifications

NC Department of Transportation(8/01/19 - 5/31/21)

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Evaluation of New Asphalt Concrete Job Mix Formula Specifications

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 5/31/21

Abstract

The North Carolina Department of Transportation (NCDOT) has recently modified the asphalt mixture design procedures in part, to increase the asphalt content and address observed cracking issues with asphalt mixtures. These changes have reduced the number of asphalt mixture types, changed compaction levels and the volumetric limits for some mixtures, and adjusted how recycled materials are considered. Given the complexity of the interactions between material parameters, the procedural changes do not guarantee that the resultant asphalt mixture designs have actually achieved the intended goal of improved durability.

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Calibration of Structural Layer Coefficients for North Carolina Asphalt Pavements

NC Department of Transportation(8/01/18 - 7/31/21)

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Calibration of Structural Layer Coefficients for North Carolina Asphalt Pavements

Sponsor: NC Department of Transportation

Start Date: 8/01/18

End Date: 7/31/21

Abstract

The North Carolina Department of Transportation (NCDOT) uses the AASHTO Guide for Design of Pavement Structures 1993 to determine the minimum pavement stiffness that ensures pavement longevity. During design, this stiffness is first determined using an iterative design process, charts, or software. Then, the engineer selects materials and layer thicknesses that provide the required stiffness by summing the contributions of individual layers. The contribution from any given layer is calculated by the product of that layer’s thickness and a structural layer coefficient that captures the overall quality and structural benefit of the material. In the NCDOT procedure, the structural layer coefficient for asphalt concrete (AC) is 0.44 (surface and intermediate mixtures) or 0.30 (base mixtures), while other material types are lower, e.g., the structural layer coefficient for unbound aggregate base materials is 0.14. While the NCDOT has had success with these structural layer coefficient values, they are based on a test road constructed and evaluated in one climate zone and with one set of materials. Modern material selection and design have resulted in substantial changes in AC and aggregate base since this time. These improvements have likely resulted in different structural contributions from these materials, which means the structural layer coefficients should be reviewed and possibly changed. Proper characterization of these layer coefficients could result in substantial cost savings to the NCDOT by reducing the required pavement thickness and/or leading to pavements that require less frequent rehabilitation and reconstruction.

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