Mitigating Potential Alkali-Silica Reaction Expansion in Airfield Concrete Pavements

Under the previous Airport Pavement Technology Program (APTP) between 2002 and 2006, much research was accomplished. Early alkali-silica reaction (ASR) research had suggested that airfield pavement deicer exacerbates ASR expansion in concrete. However, an APTP-funded Innovative Pavement Research Foundation report (IPRF 05-7) concluded that pavement deicer does not cause ASR in airfield pavements. Further APTP research demonstrated Class F Fly Ash, which is a waste product recycled from coal combustion power plants, to be an effective mitigator of ASR expansion. However, with the slowdown of coal-fired power plants resulting in limited supplies of Class F Fly Ash, other means of mitigating ASR expansion must be found. Research is needed to find alternative materials and methods for mitigating ASR expansion in concrete pavements as well as to develop a new rapid test procedure to identify ASR-susceptible aggregates.

Phase I: Complete

Phase II Mitigating Potential Alkali-Silica Reaction Expansion in Airfield Pavements

Phase 2 is using the research discoveries of Phase 1 for:

1) Benchmarking the Phase 1 approach to field work

2) Addressing the role of alkali contribution from aggregates and from SCMs

3) Broadening the investigation of reactive aggregate types including RCA and aggregates from the Mid-Atlantic region

4) Increasing the range of alternative SCMs investigated

This will include a high alkali PLC representative of the high alkali cements found in the Mid-Atlantic and Northeastern U.S.  Phase 1 has focused on three chemicals and Phase 2 will expand on evaluating these chemicals at different dosages along with placing the admixtures in concrete exposure blocks to evaluate test methods effectiveness in preventing ASR. A central part of the newly proposed work is the construction and addition of an outdoor exposure site in Pennsylvania to complement the existing network of North American Exposure sites that the research team has established.

Research team: Oregon State University, PI: Jason Ideker; the University of Texas-Austin, University of New Brunswick, RJ Lee Group

Project dates: January 1, 2022 – September 6, 2027

Performance Engineered Mixtures for Airfield Pavements

Research is ongoing with performance-engineered mixtures for highway pavements. However, the differences between highway and airfield pavements are significant, including different mixture performance requirements. These mixture-related differences need to be evaluated, understood, and cataloged. Procedures and best practices for concrete mixture optimization with airfield pavements need to be developed and incorporated into airfield specifications.

Research team: Oklahoma State University, PI: Tyler Ley; Jason Weiss, Nichols Consulting, Applied Pavement Technology, UNC-Charlotte

Project dates: April 1, 2022 – December 31, 2025

Best Practices for Rapid Repair, Rehabilitation, and Reconstruction of Concrete Airport Pavements

The aim of the work is to build upon the accelerated construction guide and case studies developed under the IPRF program to develop the guidance and standards for rapid construction projects such that the engineer, airport sponsor, and FAA have guidance they can rely on to provide quality concrete pavements under rapid construction practices.

Research team: Applied Research Associates (ARA), PI: Scott Murrell; Senseney Engineering, Kiewit Engineering Group

Project dates: March 1, 2022 – November 30, 2025

Quality Control and Quality Acceptance of Airport Pavement

In December 2018 the FAA released an update to Advisory Circular 150/5370-10, Standard Specifications for Construction of Airports. The updated specification centered around the need for improved quality control and quality assurance of airfield construction. The aim of the work is to develop a best practices manual for quality processes specifically at concrete airfield sites in the context of P-501 and military concrete pavement specifications. In addition, training materials will be prepared to help agency and contractor staff become fully conversant with the material.

Research team: University of North Carolina-Charlotte, PI: Tara Cavalline; Square One Pavement Consulting, Nichols Consulting Engineers, Hi-Way Paving, Doug Johnson; Tigerbrain Engineering

Project dates: August 1, 2022 – December 31, 2025

Best Practices for Runway Rubber Removal

This project will produce a guidance document that augments and updates ACRP Synthesis 11 by identifying and documenting best practices for runway rubber removal. It is expected that this information could be utilized by airport operators, maintenance officials, and rubber removal contractors to more efficiently restore runway pavement friction through rubber removal processes while minimizing negative impacts to the runway surface.  Although the primary emphasis is on hydro-blast processes that are sometimes associated with runway damage, the guidance should also identify and address best practices for other rubber removal processes.

Research team: Applied Research Associates, PI: Aaron Pullen; Jim Hall, Consultant; Pam Phillips, Consultant

Dates: February 1, 2023 – December 31, 2025

Effects of Diamond Grinding on Airfield Pavements

This project will investigate all relevant aspects of how diamond grinding may or may not impact concrete airfield pavements.  A further objective is to investigate and identify diamond grinding for concrete airfields best practices. The investigation will result in a report that identifies grinding impacts and best practices and provides guidance on diamond grinding that can be used by FAA, Tri-Services, and airport operators for grinding specification development and airfield operations.  The best practices guidance will be supported by a combination of literature search findings, stakeholder interviews, and documentation through case studies of projects involving diamond grinding.

Research team: Nichols Consulting Engineers, PI: Jeff Stempihar; Wiss, Janey, Elstner Associates; Applied Pavement Technologies

Dates: February 1, 2023 – December 31, 2025

Design and Performance of Thin Concrete Airfield Pavement

Although extensive research and testing were employed in the development of FAARFIELD and the design procedures in AC 150/5320-6G, most of the effort centered around heavily loaded pavement from aircraft with complex gear configurations, without significant consideration for general aviation (GA) airport pavement designed for smaller aircraft. The overall goal of this project is to examine and document the performance of GA airfield concrete pavements that are less than nine inches thick, including concrete overlays on asphalt surfaces and FDR with concrete surfaces.  Information and recommendations from the research are expected to support and aid in the development of improvements for GA airfield concrete pavement design procedures.  In addition, the outcome of this research is expected to support suggested language to update FAA Advisory Circulars and improve GA airport concrete pavement design.

Research team: Applied Research Associates, PI:  Scott Murrell; Tim Parsons and Richard Speir, ARA; Jim Mack, CEMEX; Jim Hall, JH Consulting, LLC; Chris Senseney, Senseney Engineering, LLC

Project dates: September 1, 2023 – August 31, 2026

Concrete Airfield Paving Continuity – Best Practices Guide

A critical factor in constructing quality airfield concrete pavements is the consistent delivery of concrete to the paver which enables the contractor to maintain steady paver speed and operation.

This research seeks to quantify the impacts to pavement characteristics such as smoothness and air content that may result from the paver slowing down versus stopping completely.  In addition, this project will provide guidance for contractors on managing operations so that material delivery is constant and efficient, relevant to paver speed and associated impacts.

The best practice guidance shall address impacts of paver speed and vibrator speed, along with minimum speeds versus stopping the paver entirely.  The research shall focus on impacts to characteristics that influence pavement performance, including but not restricted to pavement smoothness, consolidation, air void system, and surface finish.

Research team: Fonte & Company, PI: Matt Fonte; APR Consultants; Nichols Consulting Engineers; Oklahoma State University; Pavement Engineering and Research Consultants; Square One Pavement Consulting; Transtec Group; Jim Lafrenz; University of North Carolina at Charlotte; Wiss, Janney, Elstner Associates; Zachry Construction

Project dates: February 1, 2024 – May 31, 2027

Assessment of Flooding Resilience of Concrete Airfield Pavements

For commercial service airports (CSA) and general aviation (GA) airports alike, concrete pavements serve as a backbone of transportation infrastructure, providing runways, taxiways, and aprons essential for aircraft movement and parking. However, when these infrastructure assets are subjected to flooding, they face several threats to their structural integrity as well as short- and long-term serviceability. While GA and smaller commercial service airports do not typically handle a significant number of enplaned passengers, these airports can serve as key conduits for relief during flooding events to provide food, supplies, and personnel to local residents impacted by the occurrence. In light of climate change concerns, many areas in the United States require reassessment of flood plain potential as historic flood data may not reflect these future threats to our infrastructure.

In light of these concerns, this project aims to assess the impact of flooding on airfield concrete pavements in terms of structural capacity and material durability in a multi-faceted approach through a combination of field testing and observations, material assessment, controlled laboratory slab evaluation under flooded conditions, implementation of modern hydrologic climate and soil impacts, as well as analytical assessment of pavement responses under aircraft loads and saturated layer conditions.

Research team: American Engineering Testing, Inc., University of Alabama

Project dates: October 1, 2024 – September 30, 2027

Load Transfer in Concrete Airfield Pavements

Current FAA and Department of Defense (DoD) standards for airfield pavement are designed for aggregate interlock to provide load transfer in contraction control joints except for the last three joints at the end of a feature or adjacent to an isolation joint. The airfield pavement design assumptions include a 25 percent load transfer across the pavement joints. The FAA and DoD assume that aggregate interlock will provide for at least the design assumption for load transfer. However, many engineers question if this assumption is valid during concrete contraction in cold weather or after numerous expansion and contraction cycles. Research has shown that edge stress increases under load and that the dowels provide increased load transfer efficiency. However, in some cases the concrete deflection under load was small, therefore the dowels did not engage. So, the question remains, does doweling all contraction joints increase pavement performance enough to justify the increased cost of installing dowels in all contraction joints. Applied research is needed to assess the performance and value of dowelled versus un-dowelled contraction joints.

Research team: Applied Research Associates, Inc

Project dates: May 1, 2025 – April 30, 2027

Chicago Rockford International Airport Prestress Concrete and Fiber Reinforced Concrete (FRC) Pavement Evaluation

In the summer of 1993, an experimental concrete pavement was constructed on Taxiway F at Chicago Rockford International Airport. A 560-foot-long, 15-inch-thick conventional jointed plain concrete pavement was constructed as a control section. Two experimental concrete pavements were constructed using Type K cement.

The taxiway is expected to be rehabilitated beginning in early spring of this year. Demolition is expected to begin in April or May of 2025.

The objective of this project is to complete a performance assessment of the experimental prestressed concrete, the FRC, and conventional concrete pavement. The ACPTP’s intent is to capture any lessons learned from the design, construction, and performance of these experimental pavement sections compared to the standard FAA jointed plain concrete pavement section. The primary deliverable for this work will be a report documenting the pavement evaluation and specific lessons learned from the design, construction, and performance life of the experimental prestressed and FRC concrete pavement sections relative to the standard FAA jointed plain concrete pavement.

Research team: University of Illinois at Urbana-Champaign – Department of Civil and Environmental Engineering, Applied Pavement Technology Inc., and Valdes – Architecture Engineering

Project Dates: April 1, 2025 – March 31, 2026

Strength Acceptance

Engineers often consider strength the most important metric to evaluate concrete pavement quality. However, other parameters such as durability are often more important to long-term performance than strength. If the concrete water-to-cementitious material ratio (w/cm) is appropriate and consistent, air content is consistent and adequate for the location, the combined aggregated gradation is consistent during production, and the construction process is controlled, the concrete pavement strength is generally not a problem. In addition, testing of field concrete is only conducted to ensure that the mixture delivered and placed is consistent with that accepted in the preconstruction stage. However, many engineers have the false perception that using ASTM C78 provides an evaluation of in-place concrete strength.

The objective is to investigate the challenges with the current FAA concrete mixture acceptance criteria. Other potential methods should be investigated and assessed to determine if they could be used in place of ASTM C78 to evaluate in-place concrete properties. The primary deliverable for this work will be a report evaluating the current acceptance criteria and determining whether the use of other methods in lieu of ASTM C78 would result in a more consistent and accurate evaluation of the mixture.

Research team: TBD

Project Dates: TBD

Evaluation of Airfield Concrete Pavement Joint Sealing Practices

This project will evaluate the performance of airfield joint sealing practices through consideration of two different surface preparation procedures and three different joint sealant materials. A field evaluation and laboratory testing will evaluate the performance of joint sealant installed utilizing the current preparation method as well as the proposed method, and to develop a best practices guide for sealing and resealing airfield concrete pavements.

Research team: Wiss, Janney, Elstner, PI: Andi Mele.

Project Dates: August 1, 2025 – July 31, 2026