Rapid Slab Repair and Replacement of Airfield Concrete Pavement (2021)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

2 Introduction Background Proper maintenance and repair of concrete airfield pavements is critical to the longevity of these pavements and their ability to safely support airport operations over their design life. However, these activities can be costly and operationally disruptive, as they require closure of the pavement facility. To minimize the cost to airline operators and passengers, multirunway airfields with spare capacity can shift traffic to other runways to permit required closures for these activities. Similarly, airports with multiple taxiways or large aprons can sometimes reroute traffic or temporarily shift aircraft parking, respectively. However, these alternatives can still result in delays. At smaller, single-runway airfields or those operating at or near capacity, shutting down a runway (or an entire taxiway/apron) for an extended period to conduct repairs is simply not an option. To minimize construction impacts, airports of all sizes rely on rapid slab repair and replacement (RSRR) activities (Figure 1) done on an accelerated construction time frame, often with overnight construction windows. In such circumstances, the planning and design phases become important components in delivering an accelerated product. Federal Aviation Administration (FAA) Advisory Circular (AC) 150/5370-16, Rapid Con- struction of Rigid (Portland Cement Concrete) Airfield Pavements (FAA 2007), addresses many key components and considerations for accelerated concrete construction but stops short of providing sufficient details or specific methods to aid airport personnel or consulting engineers in making informed decisions. Furthermore, AC 150/5370-16 focuses on larger areas of concrete replacement and provides only limited information on replacement of an individual slab or smaller repairs. In addition, FAA Item P-501, “Portland Cement Concrete Pavement” in Standard Specifications for Construction of Airports (AC 150/5370-10H) (FAA 2018), does not provide specifications for early-strength concrete (ESC)—also known as rapid-strength, rapid-set, or fast-track repair materials—needed for RSRR projects. An online survey was conducted to determine current trends with RSRR. Twenty-one individuals responded to the survey, representing 10 large hub, three medium hub, one small hub, four nonhub primary, and three general aviation airports. The survey results indicated the following: • These airports possess a wide range of experience, from planning to construction. Respondents that reported no previous RSRR experience represented either nonhub primary or general aviation airports. • Stakeholder coordination and lack of skilled contractors and workforce are primary challenges. While the level of stakeholder coordination varies across airports (by size and function), the lack of skilled contractors and workforce is a universal challenge. • Airport satisfaction with RSRR performance is mixed, with shorter-than-expected service life cited as the main reason for dissatisfaction. C H A P T E R   1

Introduction 3   The airport responses indicated that although RSRR projects are common, guidance would be welcomed to improve performance. Purpose The purpose of this guidebook is to assist airport personnel and engineering consultants in selecting and executing RSRR projects and to provide relevant information for airport main- tenance personnel performing RSRR work. It covers the overall RSRR process (i.e., planning, procurement/project delivery, design, and construction) with detailed emphasis on construction considerations, materials, specifications, and practices that build on information provided in FAA AC 150/5370-16, Rapid Construction of Rigid (Portland Cement Concrete) Airfield Pavements (FAA 2007). This guidebook provides references to additional technical resources for ESC and patching materials needed for RSRR. The appendices provide case examples of RSRR programs at airports across the country along with key takeaways from RSRR construction projects that illustrate the guidance provided herein. Key Definitions The following terms are relevant to describing RSRR and are used throughout this report: • Rapid construction: Construction conducted under an accelerated schedule because of high demand and/or limited alternate routes for aircraft operations. Work is generally done over a short construction window during specified hours (i.e., nighttime, off-peak hours, weekend). The following definitions of closure are used throughout this report: – Overnight closure (<8 hours): Intended for critical areas of airfield pavement that are repaired during a short closure window (e.g., a nighttime closure that must be reopened to aircraft traffic the following morning), – Full-day closure (8–24 hours): Intended for critical areas of pavement that have some flexibility in timing for opening to traffic, and – Weekend closure (24–54 hours): Intended for critical or noncritical areas of pavement that can be closed over an entire weekend. Source: Nichols Consulting Engineers, Chtd. Figure 1. Example of rapid slab replacement on an airfield: (a) slab removal (saw cut into pieces) and (b) concrete finishing.

4 Rapid Slab Repair and Replacement of Airfield Concrete Pavement • Partial-depth repair (PDR): Removal of small areas of damaged pavement limited to the upper half of the thickness of the concrete slab and replacement with a cementitious or poly- meric repair material. PDR is a common practice for maintaining and preserving concrete pavements. When durable repair materials and proper construction techniques are selected, PDR can be a cost-effective, long-term solution for concrete airfield pavement needs. Figure 2 shows an example of PDR installation. • Full-depth repair (FDR): Full-depth removal and replacement of a portion of a slab or an entire slab by using either cast-in-place concrete or precast concrete. FDRs are predominantly constructed with cast-in-place ESC. Precast concrete slabs have been used for slab replace- ment to a limited extent on airfields in the United States and Canada. Figure 3 shows an example of the more common cast-in-place FDR. • Emergency work: Immediate PDR or FDR required to repair or replace deteriorated or damaged concrete that poses an imminent safety hazard to operating aircraft, such as by pro- ducing foreign object debris (FOD) or by affecting directional control of aircraft, or prevents use of the affected airfield pavement. • Nonemergency work: PDR or FDR required for routine pavement maintenance or preser- vation. The distressed or deteriorated concrete pavement does not pose an imminent safety hazard to operating aircraft—that is, it does not produce FOD and does not affect directional control of aircraft—but may or may not prevent the use of the affected airfield pavement. • Early-strength concrete (ESC): Concrete with early strength gain characteristics, also known as rapid-strength, rapid-set, or fast-track concrete. ESC can be categorized as follows: – Very high-early-strength (VHES) concrete: Concrete mixture with an opening-to-traffic time of 4 hours or less, typically produced with ASTM C1600 cements; – High-early-strength (HES) concrete: Concrete mixture with an opening-to-traffic time of 8 to 20 hours; and Source: Nichols Consulting Engineers, Chtd. Figure 2. Example of partial-depth repair on an airfield (damaged electrical conduit; not a dowel bar): (a) prepared repair area and (b) installed repair material.

Introduction 5   – Moderate-early-strength (MES) concrete: Concrete mixture with an opening-to-traffic time of 20 to 36 hours. • Design–bid–build: Project delivery method in which design documents are prepared in advance, competitively bid, and the bidder with the lowest price is typically awarded the contract to carry out the work. • Job-order contract: Fixed-price contract with established unit prices for work items listed in the scope, a specified term (typically multiyear), and a not-to-exceed contract value. This type of contract is competitively bid and can have multiple contractors. Current Industry Trends Survey responses from individuals affiliated with 21 airports revealed the following industry trends regarding PDR and FDR that helped shape this report: • Most PDRs and FDRs are performed on aprons, followed by taxiways and runways. • Nearly all PDRs and FDRs are done under nonemergency conditions and are typically performed by contractors. Nonemergency work is delivered under a variety of contracting mechanisms. Traditional design–bid–build, job-order contracting, and solicited quotes are the most common methods. • Fewer than half of the respondents use PDR or FDR in emergency conditions. Emergency work is generally delivered by soliciting quotes or through job-order contracting. Other delivery methods mentioned include work done by airport personnel, change order to existing contract, and through annual maintenance contracts. • Runway PDRs and FDRs are most often constructed during overnight or weekend closures on airports with multiple runways. Most work at runway intersections is completed over- night. Aprons have the lowest overnight closure requirements for PDRs or FDRs. • Prepackaged VHES or HES cementitious materials are the most frequently used material for PDR. Source: Nichols Consulting Engineers, Chtd. Figure 3. Example of cast-in-place full-depth repair on an airfield: (a) repair area ready for concrete placement and (b) concrete finishing.

6 Rapid Slab Repair and Replacement of Airfield Concrete Pavement • VHES or HES mixtures are often used for FDR. Two respondents reported using precast slabs. The opening times for FDRs are commonly determined through flexural or compres- sive strength testing. • In general, design plans and specifications are prepared for nonemergency work. For emer- gency work, some airports provide specifications and standard details, and a few airports follow contractor recommendations. Overview The remainder of this report is organized as follows: • Chapter 2 discusses RSRR planning, including identifying the need for PDR and FDR, differences between conventional and rapid construction, the RSRR decision process, stake- holder coordination, project delivery approach, and project design needs. • Chapter 3 provides detailed guidance for PDR. • Chapter 4 provides detailed guidance for FDR. • Chapter 5 provides conclusions and suggestions for future work. Profiles of RSRR programs at airports, along with case examples of PDR and FDR construc- tion, are provided in Appendix A and Appendix B, respectively.