Active Research Projects

Projects as Principal Investigator

	Identification and Prioritization of Vulnerable Roadway Segments for Proactive Resilience Planning and Response North Carolina Department of Transportation, 2023-2025 Abstract: Recent hurricanes and other extreme events have caused more than $450 million in direct damage to North Carolina’s transportation infrastructure and innumerable indirect damage from losses in mobility, additional travel times needed while repairs were made, and other impacts. This study will further the understanding of damages and potential adaptation pathways by: providing a better understanding of the failure pathways and factors contributing to pavement failures during past events; identifying the gaps and critical data linkages that hinder the use of existing NCDOT information to support resilience-based planning with respect to pavements; developing Develop a framework for identifying and prioritizing road segments as part of resilience-based improvement plans/programs; developing a design feature selection and repair strategy decision tree that considers specific features, planned needs, sustainability considerations, and possible extreme event stressors at a given pavement site, and identifying data gaps and critical data linkages that hinder the use of existing NCDOT information to support this effort and provide recommendations to improve data collection and information to support resiliency efforts. The primary outcome of the proposed research will be a design feature selection and repair strategy decision tree that considers specific features, planned needs, sustainability considerations, and possible stressors at a given pavement site.
	Evaluation of Macrotexture and Friction of Alternative Asphalt Surface Course Materials North Carolina Department of Transportation, 2023-2024 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. In recent years the NCDOT has conducted different research efforts to characterize the friction and texture characteristics of North Carolina mixes. In this project, the NCSU research team will characterize friction and texture performance of alternative surface mixture designs from other states, and identify alternative structural mixture designs that can be specified to ensure adequate friction and texture performance in North Carolina. The primary outcome of the proposed research will include new or improved asphalt mix design specifications updated to include new mixture categories that could be selected by NCDOT pavement designers in situations that warrant higher surface texture and/or friction. Given the existence of specifications for such mixes in other states, it is likely that the recommendations can have immediate impact. These outcomes can be used by the Traffic Safety and Materials and Test Units of the North Carolina DOT.
	Balanced Asphalt Mix Design for North Carolina North Carolina Department of Transportation, 2022-2024 Abstract: Current procedures for asphalt mixture design in North Carolina requires contractors to conform to volumetric requirements on the air void content, voids in mineral aggregate, and other parameters at a fixed, traffic- and layer-specific compaction effort. The presumption in this case is that the mixtures produced under the same guidelines will have similar properties. However, recently, RP2019-20 has evaluated the mechanical properties of asphalt mixtures from across North Carolina produced under the same mixture design guidelines and found notable differences in the resultant performance. In light of these issues, this research will; (1) identify the most appropriate durability related testing protocol for incorporation into mix design and quality assurance/control operations, (2) establish initial threshold limits for the test identified, (3) develop a draft balanced mix design (BMD) procedure for North Carolina, and (4) develop a draft protocol for integrating the identified performance tests into quality assurance and quality control operations.
	Mechanistic-Based Evaluation of Performance Thresholds for Engineered Surface Asphalt Mixtures Virginia Department of Transportation, 2022-2024 Abstract: In 2018, an initial effort was undertaken by Virginia Transportation Research Council (VTRC) to provide benchmark indications of performance for a number of “typical / everyday” asphalt surface mixtures produced and sampled in 2015 in anticipation of this new approach. Three fast, simple, practical, but empirical performance tests addressing different modes of distresses were selected for use as part of the BMD method. The selected tests were Cantabro test, the Indirect Tensile cracking test (IDT-CT), and the Asphalt Pavement Analyzer (APA) rut test for assessing durability, cracking and rutting potentials of asphalt mixtures, respectively. This study will build on this initial efforts to: establish links between laboratory performance-related asphalt mixtures empirical and fundamental properties (on one hand) and M-E structural pavement design (on the other hand). This is a vital step to a practical integration of mixture design and structural design; verify (or refine) the performance thresholds on the basis of mechanistic approach, rather than empirical approach; and establish and verify initial traffic-based performance thresholds for the empirical tests tied /correlated to the fundamental tests and mechanistic analyses.
	Asphalt Pavement Reflective Cracking Model to Better Address Rehabilitation Federal Highway Administration, 2021-2023 Abstract: The Federal Highway Administration (FHWA) has developed mechanistically based performance comparison models to evaluate the cracking and rutting performance of asphalt pavement mixtures. These models form the basis of an asphalt performance comparison development effort and are being implemented into a FlexPAVE software program for analyzing pavements and predicting distress. In this research study, NCSU will assess current asphalt pavement cracking models that can be applied to reflective cracking. We will further research, develop, calibrate, train, and validate a mechanistically based asphalt pavement reflective cracking model that is consistent with existing FlexPAVE methodology and performance tests; incorporate it into the FlexPAVE software and the FlexMAT and FlexMIX data analysis tools, and assess and incorporate run time improvements to the model, software, and analysis tools.
	Seasonal Effects due to Moisture Variation and Investigation of Cyclic Fatigue Temperature and End Failure on Pavement Performance Federal Highway Administration (through Advanced Research Associates), 2020-2022 Abstract: This research will involve experiments and analysis to improve the AASHTO TP 133 protocol by incorporating more scientifically based temperature selection guide and providing guidance on the maximum air void content for specimens that are subjected to this standard test method. In addition, the FlexPAVETM software will be updated to incorporate seasonal effects into the base layer and the user guides for improved usability. This research supports ongoing FHWA efforts as part of a performance-related specification framework which seeks to increase pavement life through fundamental testing and predictive relationships. Recent developments in these performance tests, adoption of standards, FlexMATTM, FlexMIXTM, and FlexPAVETM provide highway agencies and asphalt paving community with a unique opportunity to use performance tests and mechanistic models for asphalt PEMD, asphalt pavement design, and performance related specifications to integrate these different phases in pavement construction using the same test methods and mechanistic principles. These tools help link material characteristics from testing with mechanistic models to predict performance; and ultimately identify how to best design, construct, and accept a pavement.
	Ruggedness and Interlaboratory Studies for Asphalt Mixture Performance Tester (AMPT) Small Scale Dynamic Modulus Federal Highway Administration (through Advanced Research Associates), 2020-2022 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.

Projects as Co-Principal Investigator

	University Transportation Centers of Excellence Sustainable and Resilience Infrastructure North Carolina State University, PI: Tim Brock (NCSU, ITRE) Abstract: Developing sustainable and resilient infrastructure systems is vital to ensure that transportation investments deliver reliable, long term mobility options for the citizens of North Carolina. The North Carolina Department of Transportation (NCDOT) has shown a deep commitment to developing sustainable and resilient infrastructure to transportation facilities and systems across the state. To better prepare for and mitigate disruptions in the transportation network, NCDOT is developing a Center of Excellence focusing on sustainable and resilient infrastructure research. The portion of the research being carried out through this multi-institutional research consortium that involves PI Underwood will: identify and document the policy and process landscape related to NCDOT policy on asset management; develop a ranking system to aid the NCDOT in choosing strategies that manage infrastructure assets for resilience considerations; develop a decision support guideline that documents and quantifies the resilience impacts from engineering and operational strategies; identify the policy implications to implementing the guide; and and identify data sources that would aid expansion of the rankings for network prioritization.
	Safety of Earthen Stormwater Infiltration Best Management Practices (BMP) Adjacent to Highways – Phase II California Department of Transportation, PI: Narayanan Neithalath (ASU) Abstract: Stormwater best management practices (BMP) are in place to prevent pollution in stormwater runoff from Caltrans properties and also to facilitate the stormwater discharge from road infrastructure. Caltrans is required to comply with the National Pollution Discharge Elimination (NPDES) permit, including the infiltration of stormwater runoff from the highway, and required to implement soil based BMPs. As per California State Water Resources Control Board order 2012-0011-DWQ, Caltrans needs to install soil based BMPs that are capable of allowing infiltration of the 85th percentile of a 24-hour stormwater event. The area available for this purpose is typically the clear recovery zone (CRZ), including embankments and slopes that must be traversable and recoverable to meet traffic safety requirements. Thus, compliance with the NPDES must also come with adherence to traffic safety design requirements. The overall goal of this project is to highlight possible updates to design guidance, tools, and specifications for Caltrans’ stormwater BMPs to continue to refine the balance between roadside discharge requirements and traffic safety performance targets. This project builds on previous research conducted by NCSU in collaboration with ASU.
	ER23-C3-3683 – PFAS Transport and Interaction with Portland Cement and Asphalt Concrete: A Field and Laboratory Study SERDP, PI: Mohammad Pour-Ghaz (NCSU) Abstract: Portland cement concrete (PCC) and asphalt concrete (AC) exposed to AFFF have become an increasing challenge and environmental liability for the department of defense (DoD). Of critical importance to the DoD is the extent to which these AFFF-impacted materials are serving as a source of PFAS release to the environment due to PFAS leaching to stormwater runoff and migration to the substrate. The extent of this leaching for existing in-place materials, removed/stockpiled debris, and potentially recycled materials are unknown. The overarching goals of this proposal are to attain insight into PFAS leaching from AFFF-impacted PCC and AC to inform the management of these materials, understand the potential transformation of PFAS during PCC and AC recycling, and develop PFAS transport models that can translate standardized leaching test data to actual field leaching data.
	Advancing Sustainability and Resilience in Pavements: FHWA Sustainable Pavement Program Cooperative Center Federal Highway Administration, PI: John Harvey (UC Davis) Abstract: The sustainable pavement program has advanced the sustainability knowledge and practices in the area of pavements. Tangible outcomes include systematic methods for lifecycle assessment of pavements and initial guidelines on environmental product declarations. With new legislation, including the infrastructure law and inflation reduction act, there are even greater motivation for developing more sustainable and resilient pavement networks. In addition, programs like the FHWA Climate Challenge, FHWA Low-Carbon grant program, and Every Day counts initiative are further increasing demands for action and guidance from the US DOT. This proposed cooperative agreement will build upon the success of the sustainable pavements program by “exploring topics related to sustainability and resilience, including, but not limited to, sustainable and resilience infrastructure, equity, life cycle cost analysis (LCCA), LCA, social LCA, vulnerability assessment, use of low-carbon materials that are suitable to use in the US public road system, and other related topics.” The cooperative agreement will also advance the development and deployment of new technologies by delivering technical documents, case studies and tech brief, marketing/implementation plans, engaging subject matter experts, developing training tools, marketing of case studies, data analysis, compilation of findings, and supporting stakeholder engagement.
	Characterizing and Improving Binder Availability and Activity in Asphalt Mixtures with Reclaimed Asphalt Pavement Virginia Department of Transportation, PI: Cassie Castorena (NCSU) Abstract: The majority of asphalt mixtures produced in Virginia contain reclaimed asphalt pavement (RAP) due to the associated environmental and economic benefits. In addition, there is growing interest to further increase the amounts of RAP, which poses challenges with respect to mixture durability. The Balanced Mix Design (BMD) procedure, adopted by the Virginia Department of Transportation (VDOT) offers some mitigation of the challenges attributed to mixtures with relatively significant RAP content; however, this strategy is not foolproof. Building off of previous research at NCSU and VTRC, this research will explore the recycled binder availability, activity, and contribution of RAP stockpiles in Virginia in order to encompass mixtures that do not currently have BMD framework and to determine whether volumetrics and/or BMD tests are doing a sufficient job of effectively identifying and mitigating issues with RAP materials that have low binder contribution. The research effort will validate the two performance-based engineered framework developed and recommended as part of Project 177566, characterize the binder availability in typical RAP material stockpiles in Virginia, and develop guidelines or guidance documentation for how RAP availability and activity levels should be accounted for in mix design methods for Virginia, specifically those used to design asphalt mixtures with RAs.
	Proactive Prevention of Pavement Buckling Wisconsin Highway Research Program, PI: Jaime Hernandez (Marquette University) Abstract: Pavement buckling occurs when a rigid or composite pavement surface moves upward at transverse joints or cracks and it occurs, in part, because of excessive compressive forces generated at the joints of the pavement. As temperature increases, concrete slabs expands and compressive forces develop if the joint spacing is insufficient to accommodate this expansion. Buckling is a failure that is becoming more frequent in the U.S. and is usually linked to temperatures higher than historical values. Wisconsin, in particular, has experienced a steady increment in the number of buckling events over the last decade reaching close to 200 in 2021. In this project, a mechanistic model will be created to predict buckling real-life conditions. The mechanistic model will be verified using other approaches and validated with experimental measurements and will capture the effect of the variables identified in previous WHRP studies. Ultimately, the mechanistic model will be used to: assess the vulnerability of Wisconsin’s road network to heatwaves; enhance the understanding of the effects of buckling; recommend approaches to diminish the risk of buckling failure; and create a verification tool that can be merged with Wisconsin’s design, maintenance, and asset management practices.
	Evaluation of RAP/RAS Stockpiles in North Carolina and Changes in these Stockpiles Over Time North Carolina Department of Transportation, PI: Cassie Castorena (NCSU) Abstract: Past and on-going NCDOT research projects have demonstrated substantial variability in the agglomeration, recycled binder availability, and recovered binder properties of reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS) materials within North Carolina. These recycled material characteristics are not captured in current quality assurance and control measures. Furthermore, a recent operational review of asphalt plants in North Carolina indicates that unprocessed and processed recycled material stockpiling, crushing operations, and crushing frequency vary. This project will: (1) identify how recycled material stockpiling and processing practices affect the consistency of RAP and RAS properties within stockpiles and among plants, (2) evaluate the impacts of recycled material variability on asphalt mixture performance, and (3) propose modifications to the NCDOT’s current specifications to improve the consistency within and across RAP and RAS stockpiles within North Carolina.
	ARC Research Hub for Smart Next Generation Transport Pavements Australia Research Collaboration, Monash University (Prime) Abstract: The ARC Research Hub for Smart Next Generation Transport Pavements, dubbed Smart Pavements Australia Research Collaboration, or ‘SPARC’, aims to advance and transform the Australian pavement manufacturing industry. It will do this by addressing short, medium and longer-term transport challenges through high-quality, collaborative research in innovative materials, smart technologies and advanced design, construction and maintenance methods, making Australia’s transport pavements smarter and more sustainable. Australia spends approximately $20 billion annually on roads, with up to $7 billion a year spent on maintaining its 900,000 km road network, the highest per capita maintenance expenditure in the world. Roads are Australia’s largest publicly-owned infrastructure, with a replacement value between $200 and $300 billion. IThis structure, together with more extreme weather events, has generated a substantial maintenance deficit and this deficit will continue to worsen as growing population increases demand for safe transport infrastructure networks. For the first time in history, the SPARC Hub creates a national innovation platform linking the full value-chain of universities, road research organizations, contractors and road authorities to future-proof the pavements industry, making transport pavements (road, airport, and min-haul pavements) cost-effective, longer-lasting, safer, with a lower environmental footprint and ability to adapt to future transport demands, saving billions of dollars in short, medium and longer term. The NCSU role in this center will be to 1) provide advice and guidance to the Hub-Director, 2) participate in Scientific Advisory Board meetings on Hub Director’s invitation, and 3) advise the chief investigators of projects agreed between the Hub Director and the Partner Investigator of the Other Organisation.