Fundamentals of 3D Concrete Printed (3DCP) Construction Systems

BasePDH  |  Course No. 003  |  2 PDH

Source: HUD Office of Policy Development and Research

Publisher: U.S. Department of Housing and Urban Development (HUD), Office of Policy Development and Research
Date: 2023
Supporting references: ICC-ES AC509, ESR-4652 (ICON), ACI standards, NIST 3DCP material standardization work

A Note for Licensed Professional Engineers: Licensed PEs will increasingly encounter 3DCP technology in the field — whether reviewing permit submissions that rely on alternative means and methods compliance, specifying structural connections for 3DCP walls, evaluating ESR documentation on behalf of an owner or AHJ, or advising clients on emerging construction methods for residential and multifamily projects. This document provides the technical foundation needed to evaluate 3DCP systems competently, understand their code compliance pathways, and anticipate the engineering coordination challenges they introduce into conventional construction practice.

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Executive Summary

This guide provides an overview of three-dimensional concrete printing (3DCP) technology, which is a construction method using robotics to build structures with concrete material that does not require traditional concrete formwork. Five types of 3DCP technologies exist — gantry, robotic arm, robotic crawler, polar, and delta — and this report describes each type and where they are commonly used. In addition, the authors identify the leading 3DCP companies and how to acquire their technology. During this research project, the authors convened an advisory group of key stakeholders to review 3DCP construction practices, technical requirements, and the challenges of integrating 3DCP technology into a conventional construction process. The team highlighted key issues — such as design options, building code compliance, and installing building products — that engineers, builders, and developers must consider when incorporating 3DCP technology.

The research indicates 3DCP technology has the potential to significantly change the construction process in terms of labor requirements (different skill sets and fewer people), wall aesthetics (how to install conventional cladding products if preferred), and how best to demonstrate code compliance when the building code does not yet formally recognize the technology. Because the construction industry is often slow to adopt new technology, education and instruction will be needed on how best to integrate 3DCP technology. 3DCP companies have proprietary technology that is not defined based on a single voluntary standard. The American Concrete Institute (ACI) and National Institute of Standards and Technology (NIST) have led the effort to standardize materials, performance metrics, and robotics, but it has been a slow process. As of the time of this report's publication (2023), no trade association formally represented the 3DCP technology industry. The areas of robotics, supporting equipment, material formulation, and construction practices need more standardization, typically achieved through publishing industry-endorsed design guides, third-party standards, and established good manufacturing practices.

Early adopters of 3DCP technology will need to be aware of the proprietary nature of the technology and the limitations it may present in terms of equipment service support, replacement parts for robotic components, long-term warranties, and the longevity of companies. Workforce development requirements are significant: the skills needed to operate and maintain robotics differ from those of conventional framers and masons; many 3DCP companies lack deep familiarity with conventional construction sequencing; and the integration of robotics changes how existing trades such as plumbers and electricians are coordinated on the jobsite. These workforce and sequencing implications are discussed further in the Labor Requirements and How to Integrate sections.

HUD has studied innovation in construction as a means of achieving better affordable housing. 3DCP technology offers a potential solution to labor shortages and may help increase housing inventory. Nonetheless, 3DCP technology is not yet optimized for conventional construction, and too few houses have been built using the technology to identify "best practices." HUD is uniquely positioned to work with the industry to develop building code and design guidance. The authors recommend more research to define labor requirements and construction costs, as current available data are incomplete and not useful for benchmarking or comparative analysis with common construction practices.

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Introduction

This research project investigates three-dimensional concrete printing (3DCP) technology by exploring two key construction issues. First, the authors identify barriers to adopting 3DCP technology, such as the lack of building codes or standards, design and construction guidance, and the technical expertise to implement the new technology. Second, the team describes typical construction practices needed to integrate 3DCP technology into conventional construction by evaluating the installation of 3DCP walls with conventional building product components.

Two volumes present the research findings. Part 1: Identifying Barriers and Opportunities summarizes the qualitative market research results based on focus groups and surveys with home builders and contractors. The team explores the challenges and opportunities of accelerating the adoption of 3DCP technology. Part 2: An Overview of 3DCP Construction Practices provides engineers, builders, contractors, and developers with information about installing 3DCP technology. This report is the technical portion of the research, and it serves as a primer for 3DCP technology. Readers will learn about 3DCP technology options and the typical construction practices used to integrate 3DCP structures with conventional building products. Because the options for consideration are many when selecting 3DCP technology, the team developed a checklist highlighting key questions to consider when discussing options with 3DCP technology manufacturers. Generally, 3DCP technology is proprietary, and costs are not standardized for comparison with typical construction practices, so much diligence is required when considering options.

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