3D Concrete Printing
Overview
Computer Vision
Confidence
Confidence
Computer Vision
Confidence
Computer Vision
Computer Vision
Computer Vision
R&D
Regulatory
Computer Vision
Regulatory
Regulatory
Regulatory
overview
Development of 3D concrete printing (3DCP), also called additive concrete construction (ACC), began about twenty-five years ago and is now estimated to be at an overall technology readiness level of TRL 6-7. As it approaches operational readiness, 3DCP is poised to revolutionize the construction of buildings and infrastructure. This construction technique is driving change in many ways: addressing the shortage of labor through automation, reducing construction waste, increasing productivity, and lowering the carbon footprint of construction.
While this market is relatively small due to technology readiness, the number of habitable structures in the United States and around the world is growing at an accelerating pace. For 3DCP to reach its full potential, production and quality control processes must be developed that allow automation of field-based production over a wide range of ambient environmental conditions, material properties, equipment configurations, and construction applications. ARtx is focused on developing technology to automate these processes.
Deliver Confidence
ARtx is developing a revolutionary computer vision system capable of tracking the effects of the field environment over time to illustrate to builders, owners, engineers, and building officials the quality of as-built concrete elements with a particular focus on interlayer bond strength. Interlayer bond strength, a new facet of additively constructed concrete, is a major source of uncertainty introduced by this new construction technique. Flexural strength, resistance to wind uplift, resilience to freeze thaw cycles, and even retention of strength after wildfire relies heavily on the as-built interlayer bond strength. With this information in hand, current printing systems can deliver with confidence and closed-loop printing systems of the future can utilize real-time feedback for automated process control to guarantee quality.
computer vision for 3DCP
In its final form, Sentinel 4.0 is a nozzle-mounted computer vision system capable of 360° image capture along any print path. Using cameras focused on specific bands in the short-wave infrared spectrum, the system simultaneously collects data from the bead just printed ‘behind’ the nozzle and the older bead ‘ahead’ of the nozzle just prior to deposition of next layer. Based on the quality of the bead printed, and the changes observed over the interlayer duration, important information about setting rate, evaporation, shrinkage, and bonding potential can be extracted. First to market will be a stationary model, capable of monitoring a sample area of the printed wall as it gains height over the course of the project (not unlike how concrete cylinders are currently sampled to represent an entire traditional concrete pour).
Research & Development
Gathering data FAST
In its current form, Sentinel 4.0 is a translation-frame-mounted prototype capable of imaging within our portable print-through temperature control chambers. These chambers enable us to observe printed material behavior at ~50°F, ~75°F, and ~100°F during the same print. Pictured is an action shot of data collection during a print at the NIST additive construction lab in Gaithersburg, MD. In one print day, ARtx can generate 200+ bond strength samples at varied print interval times and cure temperatures, while also generating nearly a thousand computer vision algorithm data training points.
Additional training prints are scheduled during 2025 with NIST, an active commercial robotic arm printer, and an active commercial gantry printer.
Regulatory Environment
In the United States, building codes are formalized at the state level and further refined and enforced at the local jurisdiction level. In their early years, 3DCP buildings were approved after bespoke design by licensed engineers within or alongside printing companies and active education of local building officials. In June 2019, the International Code Council (ICC) approved the first acceptance criteria for 3D automated construction technology for 3D printed concrete walls: AC509. These criteria enabled the ICC Evaluation Services (ICC-ES) to formally assess 3DCP materials and designs and issue an evaluation report (ESR), enabling a more streamlined path to building official approval for specific designs.
However, 3DCP construction requirements have yet to be formally incorporated into building codes. The International Building Code (IBC) and International Residential Code (IRC), both published by the ICC, serve as the basis for state building codes in the United States. These ‘model’ codes are updated every 3 years, and thereafter are modified and adopted by individual states at their own varied pace. (For example, North Carolina will begin using the 2024 NC Building Code on July 1, 2025, which uses the 2021 edition of the IRC.) The next versions of both the IRC and IBC are expected in 2027.
ICC currently convenes an open 3D concrete consensus committee (IS-3DACT) which, in late 2024, published for public comment the first draft of ICC 1150 Standard for 3D Automated Construction Technology for 3D Concrete Walls. This document will contain significantly more guidance than has been available to date on how to properly design and test 3DCP building elements.
The American Concrete Institute (ACI) also publishes code literature, focusing specifically on concrete. The most prominent document is ACI 318 Building Code Requirements for Structural Concrete. ACI also maintains a document specifically for residential construction: ACI 332 Code Requirements for Residential Concrete. The IBC and IRC regularly cite and rely upon these ACI code documents for requirements relevant to concrete construction.
ACI currently convenes a committee focused on 3DCP (ACI 564), which is responsible for developing technical notes, an emerging technology report, and ultimately will publish guides for design and construction practice. Further, ACI has formed an independent task group to write code requirements for the construction of additively constructed walls (ITG 12). These requirements have been delivered in draft form and are under review with ITG 12, ACI 564, and other stakeholder committees. Upon approval, they will be delivered to the ACI 332 committee for further review and incorporation into the next version of the ACI 332 Code, which is expected to be completed by 2026.
ICC and ACI code literature relies heavily on the use of standard test methods to quantify construction material and structural assembly performance. These standard test methods are published and updated primarily by the American Society for Testing and Materials (ASTM). ASTM Committee C09 is responsible for concrete and has dozens of subcommittees responsible for maintaining a vast array of tests. ASTM Committee F42 is responsible for additive manufacturing technologies and has an application-specific subcommittee for construction: ASTM F42.07.07. This subcommittee has the daunting task of modifying or writing from scratch new test methods that apply to 3DCP. Of particular note, the methods for sampling material after mixing, consolidating fresh material into molds, and extracting/preparing hardened test specimens are well defined for traditional concrete construction but are significantly altered by the processes and materials used in 3DCP.
The National Institute of Standards and Technology (NIST) recognized the need for ICC, ACI, and ASTM literature to present consistent, cogent guidance to ensure public safety while aiding the timely adoption of the construction technology into the mainstream. In September 2023, NIST established the Additive Construction by Extrusion (ACE) Consortium to identify gaps, aid in the drafting of standards, and conduct tests to generate repeatability and bias statistics for new and heavily modified existing test methods.
The participants in these committees heavily overlap, consisting of printer manufacturers, 3DCP construction contractors, material suppliers, academic researchers, government agency representatives, and licensed engineers. ARtx actively participates in ACI 564, ASTM F42.07.07, and the ACE Consortium. Within the ACE Consortium, ARtx leads the task group responsible for bond strength test method refinement and round robin test design and execution.