11 Jul 2024

Sliver Spall Mitigation: Field Investigation, Laboratory Study, and Mixture Proportioning Analysis

Abstract: A combined field and laboratory study was conducted to identify factors contributing to sliver spall of concrete pavements and recommend avenues for prevention. In this study, spall density maps of eight airfields were created, and cores were taken for petrographic analysis. A companion laboratory study evaluated nondestructive testing equipment for identifying concrete prone to sliver spalling. Concrete mix designs with good and poor performance were analyzed for trends in mixture proportioning and aggregate gradation. Spall density mapping indicated sliver spalling was more likely to occur on longitudinal joints and that the distress was not solely a material or mixture design-related issue. The laboratory study concluded that surface resistivity measurements were able to differentiate edge-finishing techniques (normal versus overworked, mortar-rich edge) after seven days of curing. An analysis of particle packing theory and mixture proportioning trends showed there was substantial overlap in the gradations for good and poor performing pavement. Thus, acceptable mixture designs can produce poor quality pavement if not constructed properly. The main contributors to early age sliver spalling of concrete airfield pavement occur during pavement construction.

11 Jul 2024

Composite Material Applications and Research Roadmap for US Army Corps of Engineers Civil Works

Abstract: This report discusses and ranks the remaining research, development, and deployment opportunities for fiber-reinforced polymer composite materials in USACE marine infrastructure applications. Following the successes of at least 10 fiber-reinforced polymer composite pilot projects from 2015 to 2022, Public Law 117-58, the Infrastructure Investment and Jobs Act, allocated funding for a roadmap report that articulates lingering implementation barriers and prioritizes steps to overcome those challenges through laboratory and field experimentation. The objective analysis herein draws from real Operational Condition Assessment data generated in the field. Key opportunities lie in inspection techniques, standardized design approaches for molded components, and improved guidance to ad-dress abrasion, fatigue, and concentrated load cases at the 10-meter scale.

20 Jun 2024

Materials and Methods Used for the Expedient Repair of Concrete Pavements

Abstract: Many traditional methods for the repair and rehabilitation of concrete pavements require meticulous construction processes with specialized equipment and long material curing periods in order to develop adequate strength and durability prior to returning the pavement to service. This paper summarizes the results of research projects conducted by the US Army Engineer Research and Development Center in order to develop innovative pavement repair procedures and evaluate numerous commercial repair materials that can produce fast long-lasting repairs that facilitate the rapid re-opening of critical pavement infrastructure to traffic. This paper summarizes methods used for the certification and selection of suitable concrete pavement repair materials. In addition, this paper outlines the key activities included in expedient concrete repair processes. Thus, this paper provides a valuable summary of state-of-the-art concrete repair procedures and materials for the rapid and effective repair and rehabilitation of concrete pavements.

12 Jun 2024

Expeditionary Ground Rehabilitation for Military-Vehicle Traffic

Abstract: The research objective for this study is to identify and evaluate techniques for soil stabilization to support military-vehicle ground maneuver in contested environments. Various types of stabilizers mixed with silty sand are evaluated in the laboratory for their compressive strength at various soil moisture contents and in the field for their rutting performance. Field data are analyzed for the ability to withstand trafficking from a military ground vehicle by evaluating the rut depth and measured instrumentation data. The field testing shows that the rapid soil stabilization materials and techniques can produce repairs that withstand required traffic without traditional pavement surface materials.

3 Jun 2024

Laboratory Evaluation of Recycled Asphalt Pavement and Engineered Polymer Binder for Small Airfield Repairs

Abstract: Conducting small asphalt repairs on airfields in remote locations can be technically and logistically challenging. An alternative to cold patch products is using an engineered polymer binder (EPB) mixed with recycled asphalt pavement (RAP). This paper presents the results of a laboratory evaluation of EPB with both wet and dry RAP. Compacted specimens were tested for rut resistance, indirect tensile strength (ITS), and Cantabro mass loss (ML). The results indicate that RAP mixed with EPB exhibited substantial rut resistance with ITS and ML similar to that of conventional dense-graded asphalt. Overall, the EPB and RAP blend appears to be a promising alternative for airfield repairs.

29 May 2024

Performance of Army Corps of Engineers Mat System Using Anchorless Connections: A Follow-on Study of Site Stabilization for the Improved Ribbon Bridge Bridge Supplemental Set

Abstract: The US Army Engineer Research and Development Center conducted testing of the Army Corps of Engineers mat system with improved anchorage and connection hardware. Low-profile screw anchors replaced the ground anchorage of the existing system to reduce wear to tracks and wheels of vehicles while trafficking the system. Anchorless connections allowed the system to be placed over soils where the use of screw anchorage would be obstructed or would cause hazards to trafficking vehicles. Test tracks were constructed to evaluate the matting system with new anchorage and connection hardware over three different soils of weak sand and clay. Channelized traffic was applied to the test tracks using a loaded common bridge transporter. Performance of the updated system was evaluated with respect to results from previous testing, indicating that the improved anchorage and connection hardware increased the versatility of the matting system without sacrificing system performance.

29 May 2024

Finite Element, Petrographic, and Mechanical Analyses of Field-Cored Concrete Fairlead Beam Anchor Rods from Luke Air Force Base

Abstract: The fairlead beam is used to accomplish installation of the Barrier Arresting Kit 12 energy absorber for setback aircraft arresting system (AAS) installations at permanent operating facilities. Typical fairlead beams are affixed to a Portland cement concrete (PCC) foundation pad by a series of anchor assemblies made up of steel anchor rods set in grout inside galvanized pipe sleeves. US Air Force Civil Engineering Center (AFCEC) subject matter experts have identified a pattern of premature failures in these steel anchor assemblies when they are nondestructively inspected during AAS overhauls. The US Army Engineer Research and Development Center was tasked by AFCEC to investigate potential reasons for these premature failures. This report outlines methods and results of a finite element analysis of the anchorage, a visual and petrographic analysis of field-cored PCC anchor rods from Luke Air Force Base, and a mechanical analysis of specimens taken from the anchor rods within the PCC cores. Multiple modes of PCC distress were observed, and corrosion was evident in and around the anchor assemblies. Mechanical testing of specimens from the anchor rods indicated that an inferior grade of steel was used to fabricate these particular assemblies. Finally, observed deviations from design intention are discussed.

20 May 2024

Railroad Infrastructure Management: A Novel Tool for Automatic Interpretation of GPR Imaging to Minimize Human Intervention in Railroad Inspection

Abstract: Regular monitoring and inspection of military railroad tracks are necessary to ensure the safe transportation of military freight. Manual railroad inspection has drawbacks and limitations that can impact accuracy and efficiency. This study introduces a novel tool designed to automate Ground Penetrating Radar (GPR) imaging interpretation for railroad ballast condition assessment, aiming to reduce human intervention in inspections. The tool uses advanced signal processing techniques, such as the Short-Time Fourier Transform (STFT) and Wavelet Transform (WT), to quantify ballast fouling levels accurately, enhancing maintenance and safety protocols for railroad tracks. Validation through comprehensive testing, including two case studies, demonstrates the tool’s superior efficacy over traditional manual inspection methods. This research represents a pivotal step towards more efficient and reliable infrastructure management, ensuring critical railroad systems’ safety and operational integrity.

17 May 2024

A Dynamic Aircraft Response Model for Determining Roughness Limits

Abstract: Runway roughness poses significant risks to aircraft and aircraft personnel. Roughness irregularities can be found in both civilian and military airfields, from rutting to bomb-damaged repairs. Various methods exist for determining roughness criteria, such as discrete surface deviation evaluation and dynamic response models. Although validated dynamic response models such as TAXI-G were used extensively in the HAVE BOUNCE program from the 1970s up to the late 1990s, modern military aircraft have not undergone the same formal analysis. This paper presents the mathematical formulation and validation of the WESTAX dynamic response model. The computer program is capable of simulating the responses of different critical aircraft components while trafficking over idealized runway profiles. The validation results showed that the numerical model was capable of closely matching field data over single- and double bump events. The findings suggest that the WESTAX dynamic response model is a capable candidate for establishing aircraft roughness limits.

8 May 2024

Application of Multi-fidelity Methods to Rotorcraft Performance Assessment

Abstract: We present a Python-based multi-fidelity tool to estimate rotorcraft performance metrics. We use Gaussian-Process regression (GPR) methods to adaptively build a surrogate model using a small number of high-fidelity CFD points to improve estimates of performance metrics from a medium-fidelity comprehensive analysis model. To include GPR methods in our framework, we used the EmuKit Python package. Our framework adaptively chooses new high-fidelity points to run in regions where the model variance is high. These high-fidelity points are used to update the GPR model; convergence is reached when model variance is below a pre-determined level. To efficiently use our framework on large computer clusters, we implemented this in Galaxy Simulation Builder, an analysis tool that is designed to work on large parallel computing environments. The program is modular, and is designed to be agnostic to the number and names of dependent variables and to the number and identifying labels of the fidelity levels. We demonstrate our multi-fidelity modeling framework on a rotorcraft collective sweep (hover) simulation and compare the accuracy and time savings of the GPR model to that of a simulation run with CFD only.