Research Projects

Guidebook for Rapid Airfield Concrete Pavement Slab Replacement and Patching In Reserve

The objective of this research is to produce a guidebook that gives clear and accurate guidance to airports and airport consultants on the latest and best procedures and materials available with a proven performance record of accomplishment to provide repairs and slab replacements that both ensure on-time opening to traffic and long-term durability.

This research for the guidebook will focus on two parts: Part 1 of the research will focus on the procedures for rapid concrete removal, minimizing the need to repair the base material, whether to or not to insert dowels into the existing pavement for load transfer, and the preparation required for rapid concrete paving. Part 2 of the research will focus on the selection of materials and the proper paving techniques and equipment required for placing the selected concrete material. No one material will be selected. The guidebook will list available materials, their record of accomplishment, the material properties, their long-term durability and the equipment required. Based on this guidebook information the airport and their chosen consultant can design repairs and slab replacements for the time of available closure, aircraft loading, and availability of proven materials.

Background (Describe the current situation or problem in the industry, and how your idea would address it.)

There is a need for concrete runways, taxiways, and aprons to be repaired or replaced overnight to minimize closure times. The FAA has no specification for rapid concrete repair because it is considered a maintenance action. FAA AC 150/5370-16 Rapid Construction of Rigid Airfield Pavements provides the planning for projects but does not provide specifications. AC 150/5370-10 Item P-501 is limited to only portland cements which is insufficient for many rapid setting materials. There are no guidance or specifications for rapid setting materials, therefore airports are operating independently based upon personal experiences of the maintenance departments.
Patching materials for small patches are readily abundant and often have widely varying results because of variations in the preparation and procedures used for the repair. For large patches and full size and depth concrete slab replacement there is no standard method or material. Because there is no formal research or reports to educate the airports on recent developments in procedures and materials, therefore, airports and their chosen design consultants are most often not up to date on the best information on making their decisions.
Full slab replacement on a airfield pavement especially a runway is often needed and should be carefully planned, designed and constructed. The shorter the closure window available the harder the project becomes. In December 2017 at Sydney Airport in Australia, two 25 by 25 foot adjacent slabs were replaced on a critical taxiway in 4.5 hours and opened to an A380 super jumbo aircraft traffic. This is one of the fastest openings of full depth slab replacement including the slab removal and strength gain that has been documented.
In many cases, the concrete removal and preparation leading up to the paving is the critical path item in the closure window. There are several specialty concrete materials that can be placed, finished, and achieve sufficient strength gain in 2-4 hours. However, depending on the thickness, steel reinforcement and dowels of the existing concrete, the slab removal times can be many hours or even a workday or more. In many cases, the existing concrete is saw cut and left in place, opened to aircraft traffic for a day or two, to reduce the slab removal time. Most concrete runway pavement have dowel bars or tie bars to provide some load transfer between concrete slabs. Many slab repair procedures require that new dowels be drilled into the adjacent existing concrete before concrete placement. Depending on the equipment being used and the size of the slabs, the dowel spacing specified, this can be the largest single time consuming task is a slab repair process.
The cost of runway closure is a significant factor in the planning process for slab replacement. Although, every airport is different, there is an associated cost with a runway closure. The cost may be insignificant if there are no scheduled commercial passenger or cargo flights at night. However, it can be the most significant factor at a highly congested hub airport. For example, for the planning of the reconstruction of Runway 17C-35C at Dallas Fort Worth Airport, it was calculated that the arrival delay cost to American Airlines would exceed $600,000 for every day of runway closure. However, since these disruption costs to airlines and passengers are not directly paid by the airport itself, all too often the economic benefit lost to the community and the airlines is either not really accounted for or even dismissed by the project design team. Proper repair design should take these indirectly paid costs into account in the planning process.
If the project design firm is only considering conventional portland cement construction with 48 hours or more for strength gain, the closure window is very large and is being forced upon the users. If the project team is knowledgeable and has clear and proven specifications to use alternatives to portland cement construction, then high strength cement alternatives can be properly evaluated to determine if the higher cost of these materials is justified based upon earlier return to aircraft traffic.
By having a guidebook of procedures and materials available for rapid concrete replacement and large size patching, the project design team has a reduced risk in selecting repair and replacement alternatives. If someone has already done the research, recorded the lessons learned and documented the history of successful repairs and replacements and provided the guidebook, then each new project for repair or replacement does not have to also conduct this same research or forgo the research by taking the easier way out and only consider traditional alternatives.
There are many case examples of both US airports and non US airports using fast setting cement materials for concrete construction with considerable success. Seattle Tacoma International airport has 15 years of successful history using a fast setting cement that is not a portland cement for over 177 slabs replacements on a commercial service runway. San Diego International Airport also recently replaced slabs on a dozen gates using the same material opening the gates for aircraft in the morning. Chicago Midway airport used overnight construction with a fast setting cement to replace slabs at the intersection of two runways. runway intersection.
The airport community must also look at the pavement design, reconstruction and planning that is being done for the highway community. The California legislature has required Caltrans look at rapid setting and rapid return to service pavements. Caltrans has required for many projects on interstate pavement closure windows as short as five hours, restricted to single closure lanes and with performance penalties of $1,000 per minute for late opening. Caltrans has over 1000 lane miles in the Los Angele area using this nightly removal and replacement process.

Approach (Describe in general terms the steps you think are needed to achieve the objective.)

Proposed Tasks:
Literature review
and information gathering.
Surveys and Interviews of airports and their project consultants of successful projects to document the project
completed and the lessons learned
Develop best practices for concrete removal and preparations
Develop a comprehensiv
e list of materials that have a successful history
Strength gain and chemical composition
Material shrinkage properties
Material Alkali Silica resistance properties
Concrete durability and load resistance
Conduct field tests of the 2 most promising procedures and 3 most promising materials.
Develop a draft guidebook
Submit for review to technical committee
Develop a final guidebook and technical report of testing

Cost Estimate and Backup (Provide a cost estimate and support for how you arrived at the estimate.)

24 to 30 months and $400,000
Assuming that cooperating airports will help support the field testing. Field testing is an essential part of the research.
Hopefully an airport will step up an volunteer as a test site to conduct a field test of the implementation of the best
procedusres and materials.

Related Research - List related ACRP and other industry research; describe gaps (see link to Research Roadmaps above), and describe how your idea would address these gaps. This is a critical element of a synthesis topic submission.

There was a research project in 2005 conducted by the Innovative Pavement Research Foundation (IPRF) titled
Accelerated Practices for Airfield Concrete Pavement Construction
- Volume II: Case Studies Report IPRF
-3. However, the research was primarily a synthesis of existing procedures and case studies. In reviewing the
research, it is now evident that the researchers were unfamiliar with materials being used. For example, the case
study of the Seattle slab replacement program was cited in the
report as using a portland cement, but in fact the
cement used was a rapid setting Belitic calcium sulfoaluminate (BCSA) cement which has better durability, low
shrinkage, and faster strength gain. One replacement BCSA panel was tested 17 years later and
had achieved 11,000 psi compressive strength and 1,100 psi flexural strength. It was a good research project at the time but the case
studies and the materials available need further research now.

Idea No. 92