Lucy P. Priddy

Full-Scale Field Testing for Injected Foam Stabilization of Portland Cement Concrete Repairs

A series of foam-injected repairs was performed on a portland cement concrete (PCC) test section at the U.S. Army Engineer Research and Development Center. Repairs consisted of uncompacted backfill overlaid by a 9-in. rapid-setting cementitious cap. A series of injection tubes was inserted through the cap into the uncompacted debris backfill, and a two-component rigid polyurethane foam was injected into this backfill. The test matrix compared the performance of three different repairs using various volumes of injected foam. A fourth repair was constructed without injected foam as a control item. Three hours after cap construction, the repairs underwent simulated aircraft traffic with an F-15E load cart. The performance of the four repairs was measured by passes to failure. The results of traffic testing were used to evaluate foam-injection technology for rapid repair of PCC pavements. The performances of foam-injected repairs were also compared with poured foam and traditional full-depth backfill repairs, each capped with rapid-setting materials. Comparisons were made about pavement performance, costs, and total duration required for installing the repair. Results showed that injection of excessive foam was detrimental to the repair surface, because it induced cracking before traffic application, and could lead to premature development of foreign object damage. However, repairs using moderate amounts of foam and pure backfill sustained the required traffic levels, defined by the research sponsor, of 200 passes within 4 h of initiating the pavement repair. For cost and repair duration, those repairs that did not include foam were more effective.

Determining Rapid-Setting Material Suitability for Expedient Pavement Repairs: Full-Scale Traffic Tests and Laboratory Testing Protocol

Numerous commercial off-the-shelf products have become available for small surface repairs in portland cement concrete (PCC) pavements, providing short set times, high early strengths, and good durability to withstand heavy loads. These materials have been used successfully for both small repairs in the transportation industry and industrial applications in which the repair was less than 0.03 m3 (1 ft3). Applying these products for larger-volume repairs while still achieving a traffickable surface within 3 h of pavement repair has been a challenge. Experience gained from testing these products for full-depth repairs provides guidance for repair techniques that will expedite opening airfield or highway pavements to traffic and minimize the frequency of maintenance activities. An investigation conducted at the U.S. Army Engineer Research and Development Center, in Vicksburg, Mississippi, examined nine rapid-setting materials for repair of PCC pavements through laboratory characterization and full-scale traffic tests. Standard laboratory tests were performed to characterize the material properties over time and to provide a mechanism for assessing the material suitability for field repairs. Repairs with approximate volumes of 0.7 m3 (1.5 yd3) were constructed and evaluated under controlled traffic conditions to determine the ability of the repairs to support 100 simulated passes of an F-15E aircraft within 3 h of repair. Results of traffic tests identified seven repair materials that met these criteria. A laboratory protocol for selection of rapid-setting materials was developed based on the laboratory and full-scale test results. Use of the protocol will help prevent the selection of materials that are unlikely to meet performance expectations.

Load Transfer Characteristics of Precast Portland Cement Concrete Panels for Airfield Pavement Repairs

Portland cement concrete pavement repair technologies using precast portland cement concrete panels have been investigated for decades and recently have gained acceptance and increased use in the United States for highway pavements but have had only limited use for airfields. The recent field testing of a new airfield precast panel repair system indicated that precast panels were suitable for expedient airfield pavement repairs; the panels could withstand between 5,000 and 10,000 passes of C-17 aircraft traffic. Failure of the panels was due to spalling of the transverse doweled joints. The purpose of this study was to determine the load transfer effectiveness, or load transfer efficiencies (LTEs), of the panel repairs. A heavy weight deflectometer was used to collect defection data before, during, and after trafficking to calculate precast panel LTE on the basis of defections (LTEd) or transferred stresses (LT). The LTE values were then evaluated to determine whether current measures of effectiveness were suitable for precast panel repairs. From the results of this investigation, few of the joints provided the current military airfield design assumption of 25% LT, but the majority of the transverse joints exceeded the proposed LTEd threshold of 70% even after failure of the transverse joints. It was recommended that additional field tests be conducted without the use of rapid-setting grout in the joints before recommendations on thresholds were made.

Using Pavement Management to Support Maintenance and Engineering Policy Decisions for Small and Mid-Sized Municipalities

This article presents the development of a pavement management system (PMS) for the town of Christiansburg, VA, and the effectiveness of pavement management applications as a decision support tool. Researchers worked with personnel from the town of Christiansburg to gather inventory data and past work history on all of the pavements within the town’s network. First, the network was defined by importing existing GIS data into commercially available PMS software. The expected pavement performance was then modeled using age data along with surface condition information gathered during a survey of the network. The surface condition, age, and performance data were all combined to develop several maintenance and rehabilitation scenarios for the pavement network. The results indicated that implementing the PMS provided a framework that significantly enhanced the ability of the municipality’s engineers to determine the optimal work types and work scenarios for long-term budgeting and planning.

Development of Laboratory Testing Protocol for Rapid-Setting Cementitious Material for Airfield Pavement Repairs

Many commercial off-the-shelf products for repairing portland cement concrete (PCC) pavements provide short set times, high early strengths, and the durability to withstand aircraft traffic. Twenty-five rapid-setting cementitious materials were investigated through laboratory and field evaluations to determine their suitability for repairing critical PCC airfield pavements. Standard laboratory tests were performed to characterize the properties of the materials and provide a protocol for assessing their suitability for field repairs. Criteria for using rapid-setting cementitious materials for repairing airfield pavements were published in 2008 by the U.S. Air Force. The criteria, based on laboratory and full-scale testing, allowed users to reduce the risk of premature failure of repairs by omitting unacceptable materials from their list of potential repair materials. The American Society of Testing and Materials published a similar test protocol in 2009. On the basis of a comparison of these two certification procedures and knowledge gained through field experience, the Air Force selection protocol was further updated in 2010 to improve the material selection process. The laboratory test methods used to develop the selection protocol along with the results from the material investigations are discussed in this paper.

Development of Foam Backfill Repair Techniques for Airfield Pavement Repairs

Recent military operations have highlighted the need for new expedient pavement repair capabilities to improve current guidance on airfield damage repair. Damaged or distressed military airfield pavements must be repaired with expedient methods and durable materials to minimize the time the pavement is removed from service and to reduce or eliminate additional closure times for subsequent repairs. Extensive research was conducted to develop several airfield pavement repair techniques that could be applied across the full spectrum of military airfield repair operations. This paper focuses on the research conducted to develop a new foam backfill technology for airfield pavement repairs. Results of initial laboratory and field tests showed that rigid, poured polyurethane foam is the most applicable backfill solution for deployed locations because of its ability to expand to several times its shipped liquid volume when mixed, reducing the logistical burden of transporting aggregate backfill materials. This paper describes laboratory and field experiments that used foam backfill and prototype equipment to develop a pavement repair technique that supports threshold and objective aircraft pass levels defined for expedient airfield repairs. The research included laboratory testing, full-scale field testing, and simulated and actual aircraft traffic tests with C-17 and F-15 aircraft. Results of these tests validated and certified the foam backfill repair technique for military aircraft use. However, these experiments also identified material and equipment limitations that will require additional research before the repair technique is adopted by military repair teams. Conclusions and recommendations for future equipment and material improvements are provided.

Evaluation of Nontraditionally Surfaced Airfield Pavements

The U.S. military typically operates its aircraft on traditionally surfaced pavements such as Portland cement concrete (PCC) or asphalt concrete (AC), for which there are wellestablished methodologies for evaluating their surface conditions and structural performance. There is, however, a lack of pavement evaluation guidance for nontraditionally surfaced airfield pavements that may be encountered around the world. Aircraft operations, such as training exercises, humanitarian relief missions, or personnel evacuations may be conducted in remote regions of developing countries where access to traditionally paved airfield infrastructure meeting International Civil Aviation Organization standards is not available. Nontraditionally surfaced airfield pavements of particular interest include those with wearing surfaces comprised of sand asphalt, penetration macadam, bituminous surface treatments (applied over prepared bases), and stabilized soils/aggregates. These pavement types may be encountered in regions where airfield quality AC or PCC are either not readily available or they are too cost-, labor-, or equipment-intensive to use. Additionally, these surface types may have been used at airfields designed to support lighter aircraft with fewer operations. This paper presents evaluation procedures for predicting the performance of these pavement types for aircraft. The identification of key surface distresses and recommendations for the visual and structural assessment of each pavement type are also presented. Recommendations for improving the evaluation procedure through field verification tests are discussed.

Development of Infrastructure Management Strategies for Small and Mid-Size Airfields

The condition of airfield pavements is a critical factor in the operation of the airfield; the maintenance and repair strategies for airfields are important to effectively manage their condition. The study presented in this paper demonstrates the benefits of applying pavement management concepts to small and mid-size airfields. The results of this study suggest that applying life-cycle cost-benefit analysis, along with additional optimization techniques, can help improve the pavement evaluation and work planning processes for small and mid-size airfields. This research also shows that commercially-available software may be easily adapted for agencies with small and mid-size pavement networks. A mid-size airfield in the State of Georgia was selected as a case study to demonstrate the application of the proposed framework.