CEAT-OMP Projects 2006

Subgrade Support and Stabilization

Faculty Investigator(s): Erol Tutumluer and Marshall Thompson

Graduate Student(s): Harkanwal Brar

Overview:

Subgrade performance is a key factor in the overall performance of a pavement system. This project provides testing and analysis to establish stabilization requirements in support of the design of pavements at O'Hare.

The preliminary concrete pavement design for the O'Hare Modernization Program is:

• 15-17 inches of PCCP Surface
• 6-inch Hot Mix Asphalt Base
• 6-inch Asphalt Treated Permeable Base
• "Stabilized" Subgrade Zone (SSZ) (Thickness to be determined)
• Prepared Subgrade

North Runway (9-27) paving is programmed for the Spring 2006. The 9-27 subgrades will be primarily "fill," but there will be some cut areas. A considerable quantity of excavated soil from the "Deep Pond" was previously stockpiled and will be used as fill.

There are remaining issues concerning subgrade support and the "Stabilized" Subgrade Zone. This project will consider these issues and provide input to OMP for their evaluation and potential adoption.

Objectives:

The project objectives are:

• Establish pavement design input(s) for subgrade support.
• Establish stabilization requirements with respect to:
  • Need for subgrade stabilization
  • Stabilization admixture(s) selection
  • Stabilization depth
• Estimate "Subgrade Support" for various combinations of subgrade stabilization treatments and prepared subgrade conditions.

PCC Mix Designs

Faculty Investigator(s): Jeffery Roesler and David Lange

Graduate Student(s): Sal Villalobos, Cristian Gaedicke and Zach Grasley

Overview:

The concrete materials selected for airfield concrete pavements have a large impact on its structural and functional performance. The concrete materials must be optimized to produce a mix that can be easily mixed, placed, cured, and resist the environmental and mechanical loading that will be applied over its service life. The concrete mix design must accommodate volumetric changes at early-ages without premature cracking, limit the amount of thermal and moisture curling, and minimize the long-term contraction-expansion movements which lead to poor joint performance.

Over the past five years, the UIUC concrete pavement and materials research group has been actively involved in experimental research of airfield concrete pavement that specifically addresses concrete shrinkage, creep, and stress development; concrete fatigue, characterizing and design of concrete pavements; curling of concrete slabs; joint design; and fiber-reinforced concrete materials (1-13).

Objectives:

The objective of this research proposal is to investigate concrete material properties required to achieve long-term performance at the Chicago O'Hare International Airport (ORD) and then to develop material constituents and proportions to assure the desired material properties will be met. The project will include analysis of the existing concrete mix designs used for airfield applications, available materials suitable for the proposed mix designs, laboratory tests to determine the shrinkage, creep, and strength of proposed mixes, consideration of mix designs to produce optimal joint types and spacing, and review of fiber-reinforced concrete materials for airfield applications. Appropriate modeling of the results will be completed to extend the understanding of materials not included in the laboratory-testing program. It is expected that the following work plan will take approximately two years to complete with the time critical tasks to be completed first.

ASR and Role of Potassium Acetate on ASR

Faculty Investigator(s): Leslie Struble

Graduate Student(s): Francis Nelsony

Overview and Objectives:

The objective of this project is to study the impact of deicing chemicals on concrete pavements at O'Hare International Airport, particularly potassium acetate deicing chemicals. This project will be based on previous experience with candidate materials to the OMP project and further investigate any harmful interactions by using potassium acetate as a deicer. The main concern is to determine if use of the potassium acetate will cause alkali-silica reaction (ASR) to occur when it is otherwise not expected.

Previous work at UIUC on alkali-silica reaction has given us an understanding of the fine aggregates available for use on the OMP project. These aggregates often contain chert, which is potentially reactive to alkalies. With such aggregate, whether or not deleterious ASR expansion occurs depends on the alkali content of the concrete and on the proportion of chert in the specific aggregate. It is possible to use such aggregate in concrete, but necessary to limit the alkali content to prevent deleterious expansion. The issue in this project is to determine whether an alkaline deicer such as potassium acetate provides sufficient alkalies to produce deleterious expansion with such potentially reactive fine aggregate. If that is the case, reactive fine aggregates will need to be specifically identified and prohibited to use.

Other deicing chemicals will be researched as well to verify that they are not harmful to concrete pavement. It is believed that other existing deicers cause no deterioration to concrete, but the step is necessary for validation. It is assumed that deicers containing chlorides will not be used on OMP pavements due to concerns about metal corrosion. Potassium acetate deicing chemical should cause little to no corrosion.

A physical testing program will provide analysis of the materials and determine their usability in the presence of this deicing chemical. A database of aggregate properties and deicing chemicals will be made. Recommendations will be made to the OMP based on analysis of test results and material properties.

Aggregate Testing

Faculty Investigator(s): Erol Tutumluer

Graduate Student(s): Tongyan Pan

Overview:

Aggregates make up more than 85 percent of Portland cement concrete and asphalt pavements of which coarse aggregate occupies by far the highest weight or volume. The coarse aggregate particles typically constitute the skeleton of the aggregate structure in these layers. They are believed to significantly affect strength, stability and deformation properties, and therefore, field performances. Particularly, the coarse aggregate gradations and the morphological or shape properties such as flatness and elongation, crushed face count or angularity, surface texture, and surface area have been recognized to be critical factors affecting individually and in combination the performances of asphalt pavements. While there is a general understanding of the influence of aggregate shape properties on the performance of asphalt pavements, the specifics have been still somewhat elusive.

Objectives:

The project objectives are:

• Quantify shape, texture, angularity, and surface area properties of the coarse aggregates to be used by OMP in the various layers of new runway, taxiway, and shoulder pavements
• Provide OMP with an aggregate shape property database to efficiently rank and utilize the sources of aggregate stockpiles according to shape properties available to them
• Establish a means to develop improved and adaptable Portland cement concrete and asphalt mixture design methods and specifications that can accommodate aggregates with a wide range of physical characteristics and aggregate blending alternatives

Major benefits of optimized aggregate resource utilization and construction cost reductions are anticipated. In addition, the identification and quantification of the influence of aggregate properties on end-use performance will also be possible to identify issues linked to acceptable limits of aggregate shape, angularity, texture, and surface area to optimize performance.

Airport Wildlife Safety Management

Faculty Investigator(s): Ed Herricks and Bruce Branham

Graduate Student(s): Amanda Kiser, Theresa Kissane and Ying Wang

Overview:

Wildlife management on, and around, airports has gained importance as both the hazards and costs of wildlife collisions with aircraft are defined. Damage is related to the mass and relative velocity of colliding objects. Since both mass and velocity are important, even small birds can produce major damage to aircraft. As the mass of the animal struck increases, even low speed collisions have the potential to produce major damage with a corresponding risk to safety. An important recent factor is the increase in populations of larger birds that tend to travel in flocks, producing the potential for multiple, highly damaging collisions. A wide range of species have been involved in aircraft collisions with birds most often struck. Although collisions with mammals such as deer are not as common, the mass of even a small deer can result is major damage to both the deer and the aircraft in a collision.

The most common wildlife management techniques to protect aircraft from wildlife collisions are designed to minimize the likelihood that wildlife will be present during the critical landing and take-off phases of aircraft flight. Thus intervention procedures for wildlife at airports focus first on the airport operations area (AOA) with intervention decreasing with distance from runways. Overall wildlife management efforts recognize the importance of off-airport activity, but airports are typically limited by the property owned. Although this rule-of-thumb associated with distance from runways will not eliminate all wildlife/aircraft collision hazards, the approach does focus on area under the control of airport authorities and addresses hazards at critical phases of aircraft flight.

Objectives:

The overall project objectives are:

• Integrate OMP designs with existing and/or new and innovative wildlife management practices to minimize the attractiveness of the airport to all wildlife.
• Use the Wildlife Hazard Advisory System GIS presently being developed forORD by CEAT and Wildlife Services under the sponsorship of the FAA to provide advanced spatial analysis techniques to airport designs considering both aircraft and wildlife movement.
• Identify seed stocks and planting procedures to develop a vegetation cover for ORD that will minimize wildlife hazards to aircraft movement.
• Conduct analysis of top dressing materials for graded areas that will minimize the development of soil microfauna and corresponding attractiveness of revegetated areas to a wide range of wildlife species.
• Develop and test biobarriers as a wildlife management technique for airports.
• Evaluate all proposed stormwater conveyance, detention, and retention facilities and planning for OMP with the objective of minimizing wildlife attractants at these facilities, at present, and into the future.
• Develop a comprehensive strategy for OMP and ORD to minimize the attraction of wildlife and implement an adaptive management process based on long term monitoring.

Field Validation of Constructed Subgrade and Pavement

Faculty Investigator(s): John Popovics

Graduate Student(s): Robert Rodden and Yi-Shi Liu

Overview:

A segment of the north runway (9-27) paving is programmed for spring/summer 2006 construction. During this period, the pavement support layers will be completed and the construction of the paving layers will commence.

The pavement design for the O'Hare Modernization Program is:

• 15-17 inches of PCCP Surface
• 6-inch Hot Mix Asphalt Base
• 6-inch Asphalt Treated Permeable Base
• "Stabilized" Subgrade Zone (SSZ)
• Prepared Subgrade

Field testing and instrumentation will be conducted to characterize the strength and modulus/stiffness of the in place subgrade and pavement layers. The characterization data/information will be compared to the original design assumptions and material standards.

Objectives:

The objective of this research study is to validate the in situ properties of the subgrade, pavement support layers, and concrete pavement layers through field measurements. The field study will assist in verifying the OMP final pavement design by quantifying the strength, modulus/stiffness, and thickness of the subgrade and pavement layers through nondestructive testing (NDT). Other benefits of this study are to evaluate innovative.

Reflective Cracking and Grooving of Asphalt Overlays

Faculty Investigator(s): Bill Buttlar and Imad Al-Qadi

Graduate Student(s): Hyunwook Kim

Overview:

This study will focus on two main topics: reflective cracking and its reduction/mitigation and the performance of grooved asphalt pavements.

Reflective Cracking

Hot-mix asphalt (HMA) overlays are typically applied to existing flexible and rigid pavements when the structural or functional conditions of the pavement system have reached an unacceptable level of service. However, adequately designed overlays may still show cracking or joint patterns similar to the ones which existed in the old pavement after a short period of time. This distress is known as "reflection cracking," and can begin to occur as soon as the first winter after construction. In addition to decreasing the serviceability of the overlay, reflection cracking causes the acceleration of other pavement distresses such as the weakening of subgrade and aggregate layers through water infiltration, stripping in HMA layers, and loss of subgrade support.

The most popular methodologies for enhancing pavement resistance against reflection cracking include increasing overlay thickness, rubblizing, and placing interlayer systems. There are currently various types of interlayer systems, which have been designed to enhance pavement resistance against reflection cracking that may be installed. These include geotextile, geogrid, steel-reinforcing nettings, stress absorbing membrane interlayer (SAMI), fiber-glass, Strata, and geocomposites, which combine the main function of different geosynthetics to obtain a multi-purpose system. Recently, studies conducted at UIUC have led to the development of modeling tools that can be used to study the mechanisms of reflective cracking and to optimize overlay systems to resist this form of deterioration.

Pavement Grooving

A major consideration in safe aircraft operations is to ensure that adequate friction is present at the tire-pavement interface on runways, similar to skid resistance requirements on highway pavements. In order to enhance skid resistance at airport pavements, grooves are often sawn into concrete and HMA surfaces in areas where low friction is experienced or where high friction is needed, particularly on runway takeoff and touchdown areas. However, the insertion (sawing) of grooves into an HMA surface can accelerate several forms of deterioration, including the following: permanent deformation (rutting), thermal cracking, reflective cracking (if applicable), and raveling. In the case of permanent deformation, the presence of laterally unsupported HMA at the surface of the pavement can make the pavement more susceptible to rutting. Compared to ungrooved surfaces, several HMA properties are manifested in grooved HMA pavement surfaces. These include aggregate quality, maximum size, and gradation, asphalt binder high temperature properties, and mix volumetrics. In the case of grooved pavements, the grooves can be viewed as notches, which create points of stress 37 concentration that may result in cracking. As a result, surfacing materials having high fracture-resistance would likely be needed in order to resist thermal and reflective cracking. The grooves may also accelerate the rate and depth of penetration of asphalt binder aging, which would also tend to accelerate pavement cracking and possibly raveling.

Objectives:

The proposed objectives of this study are the following:

• Model reflective cracking of HMA overlays
• Evaluate binder properties to design materials that are more resistant to cracking, including the evaluation of environmental effects that impact distress mechanisms
• Evaluate stability of grooves in HMA surfaces

Outreach Program

Faculty Investigator(s): David Lange

Overview:

The OMP was conceived to serve economic and broader needs of the public, and these needs extend beyond physical infrastructure. Other priorities include advancement of traditionally underrepresented groups in engineering and construction; improved educational opportunities that draw students to technical career paths; internship programs that expose students to vocational, professional and entrepreneurial opportunities; and communication with the public about the benefits of OMP. The CEAT outreach program addresses priorities of the OMP, including programs in support of MBE/WBE/DBE, technology transfer programs targeted at the professional engineering community at OMP, student internship opportunities, and other educational activities within the UIUC College of Engineering.