30 Oct 2025

Thermomechanical Material Characterization of Polyethylene Terephthalate Glycol Carbon Fiber 30% for Large-Format Additive Manufacturing of Polymer Structures

Abstract: Large-format additive manufacturing (LFAM) is used to print large-scale polymer structures. An understanding of the thermal and mechanical properties of polymers suitable for large-scale extrusion is needed for de-sign and production capabilities. An in-house-built LFAM printer was used to print polyethylene terephthalate glycol with 30% short carbon fiber (PETG CF30%) samples for thermomechanical characterization. Thermogravimetric analysis confirmed the samples had 30% carbon fiber by weight. X-ray microscopy and porosity studies found 25% porosity for undried material and 1.63% porosity for dry material. Differential scanning calorimetry showed a glass transition temperature (Tg) of 66°C, while dynamic mechanical analysis found Tg to be 82°C. The rheology indicated that PETG CF30% is a good printing material at 220°C–250°C. Bending experiments showed an average of 48.5 megapascals (MPa) for flexural strength, while tensile experiments found an average tensile strength of 25.0 MPa at room temperature. Comparison with the literature demonstrated that the 3D-printed PETG CF30% had a high Young’s modulus and was of similar tensile strength. For design purposes, prints from LFAM should be considered from a bead–layer–part standpoint. For testing purposes, both material choice and print parameters should be considered, especially when considering large layer heights.

30 Oct 2025

Full-Scale Evaluation of Multi-Axial, Multi-Aperture Shape Geogrids in Flexible Pavement Applications

Abstract: The US Army Engineer Research and Development Center (ERDC) con-structed a full-scale pavement test section to evaluate the performance of three recently developed multi-axial, multi-aperture shape geogrids, referred to as HX5.5, NX750, and NX-Dev, in asphalt-surfaced highway applications. The test section consisted of a 4.2 in. thick and a 3.8 in. thick hot-mix asphalt layer placed over a 6 in. thick and 4 in. thick crushed aggregate layer, respectively. Underlying the crushed aggregate layer was a 2 ft thick clay subgrade that had a 6% California Bearing Ratio. Simulated truck traffic was applied using ERDC’s heavy vehicle simulator–transportation with a dual-wheel tandem axle truck gear. Rutting performance and instrumentation response data were monitored at multiple traffic intervals. Observed rutting in the geogrid test items was approximately one-third of that in the unstabilized item, in which was a meaningful performance improvement. Instrumentation response data indicated that the geogrid inclusion pro-vided a stiffening effect that altered the anticipated pavement response. An analytical investigation showed that traditional layered elastic analysis techniques did not adequately describe the pavement response with geogrid inclusion. A robust model that included material nonlinearity and a geogrid interface model provided a closer approximation to the measured subsurface response.

7 Oct 2025

Gravel Investigations Informing Resource Management Within the Lower Mississippi River

Abstract: This report integrates available information about gravel deposits within the Lower Mississippi River (LMR) from previous studies coupled with new analysis to identify reoccurring observed gravel locations. This study also summarizes spatial and temporal trends of bed material sediment characteristics, focusing primarily on gravel. Moreover, selected data sets from previous studies, and field and aerial observations have been added to a geographic information system (GIS) database housed in ArcPro to illustrate observed gravel locations. Last, a literature review documenting the ecological importance of gravel bars to riverine fauna and a brief discussion of potential technologies to support conservation efforts are included. Major findings summarized herein are (1) the presence of gravel deposits tend to decrease in a downstream direction along the LMR; (2) qualitative analyses of aerial videos suggest that gravel-predominant bars are more common between River Miles 953 and 681; (3) past investigations have documented gravel sizes at rivers bars ranging from pebbles to boulders; (4) the gravel content in LMR bed material samples has decreased since 1932; and (5) more detailed surveys are needed to better delineate the spatial extents and depth of gravel bars and identify suitable technology to detect potential buried gravel.

2 Oct 2025

Modeling Thermocouple Placement in a CUBI Test Fixture

Abstract: This report describes an effort to model the response of temperature thermocouples mounted on a multisurface CUBI test fixture as a means to document potential thermocouple error sources. (CUBI is a euphemistic term that describes an assembly of contiguous cubic or rectangular solids.) The thermal solver within the commercially available Multi-Service Electro-Optical Signature (MuSES) Infrared (IR) was employed for modeling and analysis. Modeling was divided between the development of models to study individual temperature sensors and the incorporation of many such sensors into a full-up CUBI apparatus. The MuSES model of the simple plate in replicating analytic results to a high degree of accuracy, thus validating the MuSES solver. Additionally, MuSES modeled a CUBI fixture as a 2D shell in an outdoor environment. This model was run with and without attached sensors. The difference in temperature of a particular sensor and of the underlying CUBI surface with the sensor absent provided a prediction of the measurement artifact introduced by that sensor.

2 Oct 2025

Field Study of Nontraditional Airfield Pavements

Abstract: Airfield pavements in contingency environments might not meet current design standards or might have deteriorated significantly. This study developed performance models for operating C-17 and C-130 aircraft on austere pavements, termed nontraditional airfield pavements. Field evaluations were conducted at six exemplar pavement sections to determine their structural capacity and remaining service life. The structural capacity of these pavement sections was first evaluated using nondestructive and semi-destructive test methods. The evaluations were performed using a single-wheel aircraft-loading simulator operated at two tire inflation pressures while maintaining total aircraft load. Field performance data included sur-face pavement deformation and structural deterioration. Forensic test pits were excavated to document the pavement structural design, material characteristics, and potential failure mechanism. This study found that an expedient contingency operation (100 passes or fewer) of a C-17 could be satisfactorily accomplished, and the service life could be potentially greater for a C-130. Reducing the tire inflation pressure did not always influence the pavements’ performance. The lightweight deflectometer showed potential as a portable pavement-monitoring tool. ERDC developed an improved performance-prediction technique for nontraditional airfield pavements and now propose further implementation to predict service life of other air-field pavement types.

29 Sep 2025

Physicochemical Kinetics of Rapid Soil Stabilization Using Calcium Sulfoaluminate-Based Cements

Abstract: Rapid stabilization of weak soil offers a promising option for quick infrastructure development and soil repair. The interaction between the rapid stabilizer and the soil is critical in defining its strength and durability. This study investigates the physicochemical effects of using Calcium Sulfoaluminate (CSA) cement-based stabilizers for rapid stabilization of weak clays, focusing on early age (<1 day) reaction kinetics and its effect on the short-term and long-term engineering characteristics. Geochemical modeling is proposed to model the chemical kinetics and predict the formation of strength-enhancing products in the stabilized soil mixtures. The study investigates the unconfined compression strength and durability (cyclic wetting and drying) of stabilized soil. Results showed stabilizers with a higher proportion (50 wt. percentage or more) of CSA (CSA-rich) achieved up to 80 % of the 28–day strength in 60 min after stabilization. Mineralogical characterization using X-Ray Diffraction, Thermogravimetric Analysis, and Scanning Electron Microscopy, identified Ettringite in CSA-rich stabilizers and Calcium-Silicate-Hydrates (C-S-H) in stabilizers with a higher (50 wt. percentage or more) proportion of Portland Cement (PC-rich) stabilizers as key strength-enhancing products. Integrating the modeling results with the engineering and mineralogical characterization provided valuable insights into the rapid stabilization mechanisms of CSA cement.

29 Sep 2025

Demonstration of Innovative Patching Technologies for Asphalt Pavement Sustainment

Abstract: iHMA and RapidPatch are two asphalt repair materials developed at the US Army Engineer Research and Development Center (ERDC) to provide asphalt patching materials that are readily available, support rapid return to traffic, and yield high quality, long-term performance solutions. The primary objective of this project was to complete multiple demonstrations of asphalt patching with iHMA and RapidPatch at four installations in different climate zones around the United States. These locations included Fort Wainwright (Alaska), Fort Drum (New York), Fort Huachuca (Arizona), and Bradshaw Army Airfield (Hawai‘i). Overall, demonstrations were completed successfully in all climates, providing an opportunity to evaluate patching technologies in real-world environments, some of which are considered untraditional conditions for repairing asphalt. In total, 111 tubes of iHMA and 90 buckets of RapidPatch were used to complete 55.3 ft3 and 49.8 ft3 of patching, respectively, with patch sizes ranging from 4 ft2 up to 20 ft2. Both iHMA and RapidPatch repairs performed well under accelerated trafficking at all installations, exhibiting no more than 6 mm of rutting (less than 1⁄4 in.) after 1,000 passes of heavy truck loading. After 9 to 12 months of operational traffic and environmental exposure, both iHMA and RapidPatch repairs have performed well.

25 Sep 2025

Train Loadings on Bridges for US Army Installations: Guidance

Abstract: Railroad bridges on US Army installations must be rated to determine the safe load limits for the trains that utilize them. In addition to the standard Cooper E-80 loading required by the Federal Railroad Administration, specific locomotives and railcars that use the bridges must also be considered in the load ratings. For that purpose, this report documents the authors’ efforts to compile detailed dimensional- and axle-loading data on all Army-owned locomotives and railcars and then to develop a set of Army-specific rail equipment loadings for use in bridge load ratings. This report provides a detailed description of the data compilation and load development process that resulted in the Army-specific rail equipment loadings.

23 Sep 2025

Naval Expeditionary Runway Reconstruction Criteria: Evaluation of Full-Depth Reclamation for P-8 Aircraft Operations

Abstract: A structurally failed asphalt pavement section was reconstructed to investigate the full-depth reclamation (FDR) technique. The full-scale FDR pavement section consisted of six different test items containing different FDR material blends, a minimum asphalt layer thickness (i.e., 2 in. and 3 in.), and FDR-surface pavements (i.e., asphalt-surfaced and unpaved pavements). The FDR layers were stabilized with a combination of an asphalt emulsion and Portland cement. A heavy vehicle simulator was employed to simulate the loading conditions of the P-8 Poseidon aircraft. The performance of the full-scale pavement section before and after the FDR reconstruction was compared. The FDR technique was satisfactorily implemented to restore the structural capacity of a failed asphalt pavement. The pavements with FDR layers yielded at least two times more allowable passes than the conventional pavements. The FDR-surface pavement sections also demonstrated structural competency to support the expedient operation of heavy aircraft. The performance data generated from this project must be implemented to improve current practices in the design and evaluation of airfield asphalt pavements containing an FDR layer.

19 Sep 2025

Bridging the Impact Response of Polymers from the Nanoscale to the Macroscale

Abstract: Impact from a fast-moving object is a common event, but it can vary greatly in terms of scale, speed, and energy depending on the specific case. Recently, it has been suggested that scaling analysis can be used to relate the impact performance of materials at the nano- and microscale to their behavior at the macroscale, which is relevant for most applications. In this study, we explore the broad applicability of this approach by conducting micro- and macroprojectile impact tests on polymethyl methacrylate and polycarbonate films. By applying Buckingham 𝛱 dimensional analysis to all the impact test results, we demonstrate that the minimum perforation velocity is directly related to the geometric and material properties of each system across a broad range of size and energy scales. Interestingly, we find that the failure stress of the polymer, a critical material property that defines perforation resistance, can be empirically determined based on the deformation of the specific impact test.