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Complex military operations often result in U.S. forces remaining at deployed locations for long periods. In such cases, more sustaina-ble facilities are required to better accommodate and protect forward-deployed forces. Current efforts to develop safer, more sustaina-ble operating facilities for contingency bases involve construction activities that require a redesign of the types and characteristics of the structures constructed, that reduce the resources required to build, and that decrease the resources needed to operate and maintain the completed facilities. The Automated Construction of Expeditionary Structures (ACES) project was undertaken to develop the capa-bility to “print” custom-designed expeditionary structures on demand, in the field, using locally available materials with the minimum number of personnel. This work investigated large-scale automated “additive construction” (i.e., 3D printing with concrete) for con-struction applications. This report, which documents ACES materials and testing, is one of four technical reports, each of which details a major area of the ACES research project, its research processes, and its associated results. There major areas include System Require-ments, Construction, and Performance; Energy and Modeling; Materials and Testing; Architectural and Structural Analysis.

The need to conduct complex operations over time results in U.S. forces remaining in deployed locations for long periods. In such cases, more sustainable facilities are required to better accommodate and protect forward deployed forces. Current efforts to develop safer, more sustainable operating facilities for contingency bases involve construction activities that redesign the types and characteris-tics of the structures constructed, reduce the resources required to build, and reduce resources needed to operate and maintain the com-pleted facilities. The Automated Construction of Expeditionary Structures (ACES) project was undertaken to develop the capability to “print” custom-designed expeditionary structures on demand, in the field, using locally available materials with the minimum number of personnel. This work investigated large-scale automated “additive construction” (i.e., 3D printing with concrete) for construction applications. This document, which documents ACES energy and modeling, is one of four technical reports, each of which details a major area of the ACES research project, its research processes, and associated results, including: System Requirements, Construction, and Performance; Energy and Modeling; Materials and Testing; Architectural and Structural Analysis.

In 2014 the University of Nebraska, Lincoln (UNL) was engaged in field testing program to investigate a soil moisture mapping system as a crop management tool. In conjunction with this work, the US Army Engineer Research and Development Center, Cold Regions Research and Engineering Laboratory (ERDC-CRREL) deployed a team to perform soil characterization and strength measurements at three agricultural test sites. The primary objective was an investigation of the Lightweight Deflectometer (LWD) as a soil surface strength tool for the purposes of assessing bearing capacity of soft soils. The LWD measurements were performed with those from more “standard” tests, i.e. the Dynamic Cone Penetrometer, Cone Penetrometer, and Clegg Impact Hammer to determine if the LWD produced results that compared with these methods. The strength test data were also used to calculate California Bearing Ratio (CBR) values using existing equations in order to see if the different test methods produced similar CBR values that could in turn be used to predict the bearing capacity of the sites. The secondary objective was to compare the strength data with the corresponding soil water content data taken by UNL to determine if soil moisture was an indicator of soil strength.

Purpose This paper aims to qualify traditional concrete mixtures for large-scale material extrusion in an automated, additive manufacturing process or additive construction. Design/methodology/approach A robust and viable automated additive construction process must be developed that has the capability to construct full-scale, habitable structures using materials that are readily available near the location of the construction site. Accordingly, the applicability of conventional concrete mixtures for large-scale material extrusion in an additive construction process was investigated. A qualitative test was proposed in which concrete mixtures were forced through a modified clay extruder and evaluated on performance and potential to be suitable for nozzle extrusion typical of additive construction, or 3D printing with concrete. The concrete mixtures were further subjected to the standard drop table test for flow, and the results for the two tests were compared. Finally, the concrete mixtures were tested for setting time, compressive strength and flexural strength as final indicators for usefulness in large-scale construction. Findings Conventional concrete mixtures, typically with a high percentage of coarse aggregate, were found to be unsuitable for additive construction application due to clogging in the extruder. However, reducing the amount of coarse aggregate provided concrete mixtures that were promising for additive construction while still using materials that are generally available worldwide. Originality/value Much of the work performed in additive manufacturing processes on a construction scale using concrete focuses on unconventional concrete mixtures using synthetic aggregates or no coarse aggregate at all. This paper shows that a concrete mixture using conventional materials can be suitable for material extrusion in additive construction. The use of conventional materials will reduce costs and allow for additive construction to be used worldwide.

This report investigated the application of accepted methods of pavement structural evaluation to independently assess the potential structural benefit of asphalt geogrid reinforcement of an operational flexible highway pavement. The asphalt interlayer consisted of an elastomeric polymer coated fiberglass grid with an open configuration. The reinforcing grid was installed in the asphalt layer during construction of a maintenance overlay and has been subjected to trafficking for several years. The structural evaluation included a geotechnical investigation and nondestructive testing using a falling weight deflectometer. Field testing was conducted when both air temperatures were above 50°F and no recent precipitation events had occurred. Standard testing methods were applied during the field data collection and back-calculation procedure. The back-calculation results showed no clear quantifiable benefit from including the reinforcing grid in the asphalt layer, but this study developed a methodology to test and evaluate in situ flexible pavements with asphalt grid reinforcement. The authors recommend that a future structural evaluation be completed to monitor any changes in the pavement’s performance.

The National Science Foundation operates stations on the ice sheets of Antarctica and Greenland to investigate Earth's climate history, life in extreme environments, and the evolution of the cosmos. Understandably, logistics costs predominate budgets due to the remote locations and harsh environments involved. Currently, manual ground-penetrating radar (GPR) surveys must preceed vehicle travel across polar ice sheets to detect subsurface crevasses or other voids. This exposes the crew to the risks of undetected hazards. We have developed an autonomous rover, Yeti, specifically to conduct GPR surveys across polar ice sheets. It is a simple four-wheel-drive, battery-powered vehicle that executes autonomous surveys via GPS waypoint following. We describe here three recent Yeti deployments, two in Antarctica and one in Greenland. Our key objective was to demonstrate the operational value of a rover to locate subsurface hazards. Yeti operated reliably at −30 °C, and it has has good oversnow mobility and adequate GPS accuracy for waypoint-following and hazard georeferencing. It has acquired data on hundreds of crevasse encounters to improve our understanding of heavily crevassed traverse routes and to develop automated crevasse-detection algorithms. Importantly, it helped to locate a previously undetected buried building at the South Pole. Yeti can improve safety by decoupling survey personnel from the consequences of undetected hazards. It also enables higher-quality systematic surveys to improve hazard-detection probabilities, increase assessment confidence, and build datasets to understand the evolution of these regions. Yeti has demonstrated that autonomous vehicles have great potential to improve the safety and efficiency of polar logistics. © 2012 Wiley Periodicals, Inc.

Conventional cold-weather concreting is expensive and very energy inefficient. Common practice requires artificial heating of the raw materials and the surrounding environment to create suitable curing conditions for normal concrete. Antifreeze concrete is a new approach to cold-weather concreting without the need for artificial heating. This saves time, money, and energy. The antifreeze concrete technology has been proven in numerous full-scale field demonstrations and is compatible with current concrete construction practices. A laboratory study established the practicality of using antifreeze concrete and developed the tools to mix and cure concrete in subfreezing temperatures. Eight candidate antifreeze formulations were developed in the laboratory and subjected to initial screening tests that showed they were capable of being workable, entraining air, and meeting the design freezing point. Performance testing showed that the strength gain when cured at -4°C is as good as conventional concrete cured a...

Tactical mobility analysis techniques were merged with land management strategies to assess potential impacts of vehicle operations on training areas for rangeland planning and management. A vehicle mobility analysis was performed for a suite of vehicle types using the NATO Reference Mobility Model (NRMM II). Input parameters include terrain information (soil type, slope, vegetation, surface roughness, soil strength), terrain surface condition based on climate (terrain strength, freeze–thaw, moisture content, snow cover), and vehicle specifications (tire, power train, weight on each axle, ground clearance, dimensions, ride). The vehicle performance was spatially mapped over the terrain for different seasons of the year and used to calculate the maneuverable acreage, which was compared to acreage needed for training requirements. This can be related to land capability based on expected training impact (Maneuver Impact Miles, MIM) and Land Condition Curves which link training density to land condition. This methodology can be used to determine the suitability of training lands and the degree of land management or rehabilitation expected. The methodology was applied to the transformation of the Alaska training lands to support a new brigade unit called the Stryker Brigade Combat Team (SBCT3), but is equally useful for other training areas and military units. For summer use, Alaska training lands are capable of supporting four times the projected training requirements. For winter, when the ground is frozen, more than 10 times the area needed was available.

Remediation of a Superfund site in Stratford, Connecticut, involved stabilization of the subgrade with portland cement. Part of the remediation site was to be used as a parking area. The stabilized soil was to be covered with natural base/subbase course materials and capped with an asphalt concrete cover. During the course of the remediation, a base-course layer could not be placed prior to the onset of winter. A field study was conducted to quantify any changes in the mechanical properties of the open stabilized subgrade subjected to freeze-thaw cycling during the winter of 1996-1997. Field evaluation was conducted with pavement industry tools: the Clegg impact hammer and the dynamic cone penetrometer. Evaluation results show the viability of the Clegg hammer as an instrument for quality assurance and also show that there can be up to 50% loss in compressive strength of the subgrade within the uppermost layer of the material caused by freeze-thaw cycling.

A study was conducted on full-scale pavement test sections to assess base reinforcement with geogrid in flexible pavements. Two thicknesses of asphalt and two thicknesses of base course were tested. Four test sections were reinforced with geogrid placed at the base/subgrade interface, and there were four matching control sections constructed on one subgrade. A heavy vehicle simulator loaded all the test sections. After construction, the subgrade was conditioned to a lower modulus value by adding water to the test sections, and the response was monitored using falling weight deflectometer (FWD) testing. In addition, FWD testing was also performed immediately prior to and after traffic loading in order to monitor the modulus of the subgrade and base layers. The subgrade modulus values were greatly affected by water content, but also experienced a significant decrease from immediately before to immediately after application of traffic. The modulus values then recovered over time. The base modulus values demonstrated a similar response when traffic was applied. The average modulus values for the base courses reinforced with geogrid were on average 1.34 times those for the base courses in the control sections throughout the project.

The Corps of Engineers is embarking on the next phase, Phase III, of Cold Weather Admixture Systems (CWAS). CWAS is an innovative approach to conventional cold weather concreting. Since its inception several years ago, the Corps continues to develop this technology to benefit the user and change the approach to winter concreting. Chemical admixtures are routinely used to accelerate cement hydration and promote early strength gain in fresh concrete. To date, no single admixture, when used within the manufacturer's recommended dosage, is capable of preventing fresh concrete from freezing. External heating is still required to maintain a curing environment. This necessitates additional resources (time and money) and is expensive, given volatile energy prices. To fill this void, CWAS uses an `off-the-shelf' approach of suites of admixtures that, when used in combination, protect fresh concrete to an internal concrete temperature of −5°C. The cement hydrates and the concrete gains strength even when the temperature is below freezing. Phase I showed the feasibility of the CWAS approach and uncovered potential long-term durability benefits. Phase II further investigated CWAS formulations using elevated dosages of chemical admixtures. Throughout this time period, numerous field demonstrations have been conducted to introduce the CWAS approach to State Departments of Transportation and the U.S. Army. CWAS is catching on. The next phase seeks to optimize the admixture combinations tailoring the mixes to site-specific conditions based on the geometry and forecasted weather conditions. This capability makes CWAS a powerful tool providing users greater flexibility for winter concrete construction projects.

The Army's Future Combat System (FCS) relies on agility and speed, including the ability to conduct air transport operations where no runways exist, and where engineers cannot be pre-positioned. One of the most difficult problems is locating large, smooth, flat, and obstruction-free areas that are sufficiently firm to support at least one aircraft operation, and preferably many. The Opportune Landing Site (OLS) program demonstrated the use of remote sensing technology and state-of-the-ground forecast tools to accelerate the process of selecting OLSs. To evaluate the quality of the selected OLSs, ground truth measurements were conducted at Fort Bliss in New Mexico. Before conducting field measurements, several sites identified by OLS software were visually inspected to evaluate and select a suitable OLS for field testing. Evaluation procedures were based on Air Force Civil Engineer Support Agency (AFCESA) recommendations for evaluating airfield pavements. Soil strength and moisture measurements were made at several locations along the OLS, and overall quality was evaluated during three seasons. Assessment software was able to predict an OLS adequate for landing a C-130, but not capable for a C-17. This was true for all three field assessments at Fort Bliss.

A 3-D Finite Element Model (FEM) was constructed of a loaded C130 tire rolling over a frozen unpaved runway. The runway was constructed of two layers, one frozen and one unfrozen, each of varying thickness, but the combined thickness was fixed. The material model used in the dynamic FEM simulation represents a frostsusceptible soil, which was used in full scale unpaved road tests at CRREL’s Frost Effects Research Facility (FERF), and was calibrated with triaxial tests and validated against direct shear test data. The area of interest in both models is the interaction between the frozen (top) layer and the unfrozen (bottom) layer. Stress and strain data collected from the dynamic FEM simulation and a prior single point layered elastic (SPLEM) simulation were compared, along with the capabilities of each model. Initial findings show that the single point layered elastic model is much faster at obtaining results for a single point, but it can only solve problems with pure elastic material. The FE model can solve problems with any material and the results can be viewed at any location or point in time during the run. The FEM visually represents what is happening in the soil around the tire as it rolls along the surface, while the static SPLE model only predicts what is occurring directly below the tire.

This project was conducted to assist in predicting the effects of freeze and thaw cycling on Tilcon common granular fill during the freezing season. This material is being used as the subbase material in the proposed pavement structure at the Raymark Superfund site in Stratford, Connecticut. Based on the initial laboratory results of the Tilcon material performed at CRREL, the amount of fines passing the no. 200 sieve was found to be in the vicinity of 20%, of which approximately 14% was finer than 0.02 m. Results from the frost heave tests indicate that when the Tilcon material is saturated, based on the rate of heave, the material is classified a high to very high frost susceptible material. In the saturated condition, the material is classified as a low to medium frost susceptible material. Computer simulations were run to predict the amount of frost heave and frost penetration that may be expected on this site during the freezing season. Results from the laboratory frost susceptibility tests and com uter simulations were then used to estimate the amount of cumulative damage to the pavement structure during its design life.