Combat engineers in the US Military are routinely tasked with constructing or repairing infrastructure to support maneuver operations. Due to its versatility, additive construction (AC) has the potential to transform how battlefield mobility and counter-mobility construction missions are accomplished. A major challenge, however, is that most AC concrete structures use proprietary pre-blended mixes or very select high-quality materials. This is in an effort to maintain consistent and reliable printability and strength, and because many other variables affect the performance of AC concrete and mortar even when tight material constraints are met (e.g., environmental conditions, printing equipment, printing parameters). In expeditionary missions, the material options available are greatly limited, and sourcing and transporting select materials would require a large logistical footprint. Increasing the use of native or indigenous materials in AC concrete mixes is critical for AC to be a feasible option for military operations.

This presentation will focus on the state-of-the-art AC materials research carried out as a part of the ACME Tech research program. ACME Tech (Additive Construction of Maneuver Enabling Technology) is comprised of researchers from Applied Research Associates, the University of Arkansas, Iowa State University, and Robotic Construction Technologies and is funded by the United States Army Corps of Engineers – Engineering Research and Development Center (USACE ERDC). The goal of the program is to advance AC technology by developing structural designs for mobility and counter-mobility items, material mixtures using indigenous materials, AC slicer software solutions, and a mobile AC equipment package for military construction.

An integrated and multifaceted approach consisting of constituent material characterization, mix design, and AC performance was taken to examine the use of indigenous materials in AC concrete mixtures. A variety of native materials were sourced from across the globe and characterized. Series of mixture designs, batching, and testing were carried out to systematically evaluate the effects of changing mixture proportions, index properties, and additives on the fresh and hardened concrete properties. The fresh properties were characterized using a range of tests performed on sampled material (e.g., Vicat, penetration resistance, flow table, rheometer, green strength) as well as in situ monitoring (e.g., filament shape retention, buildability). The hardened properties were characterized using a variety of tests following ASTM procedures (e.g., uniaxial compression of cylinders and mortar cubes, three-point bending, modulus of elasticity, triaxial shear, indirect tensile, direct tensile) as well as numerous AC-specific tests focused on capturing the intrinsic characteristics of printed specimens (e.g., double shear, indirect tensile of layered filaments, single filament-based element testing). Printability and the associated open extrudability window were also evaluated with multiple AC equipment systems and types including the Imer Small 50 pump, 3D potter SCARA Elite V2 robot with and without auger, MAI Multimix-3D pump, and a unique RT15 AC system developed by Robotics Construction Technologies Inc.

The findings will be presented and discussed, and recommendations will be provided regarding the most appropriate materials characterization and AC characterization tests. Relationships between the index properties, fresh and hardened properties, and printing performance will also be presented to improve the overall understanding of the use of indigenous materials in AC mixtures.

Date and Time
Friday, November 8, 2024
1:30 PM - 3:00 PM

Location
Huntington Room

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