3D Printing of Concrete

State of the Art and Challenges of the Digital Construction Revolution

Arnaud Perrot, Arnaud Perrot

• Editorial: Wiley-ISTE
• Año: 2019
• ISBN:
  9781119610786
• Edición: 1
• Categoría: Tecnologia e ingegneria
• Categoría: Salute e sicurezza sul lavoro

The introduction of digital manufacturing techniques, such as 3D printing applied to concrete material, opens up new perspectives on the way in which buildings are designed. Research on this theme is thriving and there is a high rate of innovation related to concrete. At the same time, the first life-size constructions made from printed concrete are emerging from the ground. This book presents state-of-the-art knowledge on the different printing processes as well as on the concrete material that must adapt to these new manufacturing techniques, such as new hardware and new printers for concrete. The possibilities in terms of architectural design are discussed as well as the pathways that remain to be uncovered. The book also explores the challenges that researchers and companies expect to overcome as they get closer to democratizing this potential revolution that is the digital manufacturing of concrete.

1
3D Printing in Concrete: General Considerations and Technologies

1.1. Introduction

The application of 3D printing and the introduction of digital technologies into the concrete construction sector are the result of the appropriation and repurposing of technology initially developed for other materials, such as resins and plastics.

This would be a good time to introduce the need to improve performance on the construction site.

The construction industry accounts for 13% of industrial expenditures worldwide, but only 1% of annual growth in productivity. It is a sector that has a long tradition of low productivity and stunted technological capabilities, in comparison with the technical developments in other industries that have largely automated and digitized their manufacturing processes. The reasons for this conservative outlook are numerous and often stem from the uniqueness of each building, which, in practice, does not allow processes to be reproduced and, to a certain extent, limits the technical framework on the site. The low productivity brought about by methods that are a burden to implement results in high production costs, which make it difficult for companies to develop. For instance, operations using concrete castings account for 50–75% of the cost of the structural work, while concrete and steel materials account for only a small percentage of manufacturing costs.

Automation on construction sites is one of the methods suggested by the study published in 2017 by McKinsey [MK 17]. The introduction of a disruptive technology such as 3D printing would bring the construction industry into the digital realm, leading to a rise in the technical levels of workers and expanding the possibilities for building design and architecture.

In order to better understand 3D printing methods, first, we will provide an overview of 3D printing in general, as well as the different methods initially developed. Next, we will present the different methods used for concrete, inspired by the initial techniques used for plastics, ceramics and metals. Finally, in the last section, we will attempt to classify the concrete printing methods proposed in the literature [DUB 17].

1.2. General considerations for 3D printing and additive fabrication

1.2.1. What is 3D printing?

There is no universally recognized definition of 3D printing.

Many different definitions and terms are used or combined to describe 3D printing, such as additive fabrication, computer-aided or digital fabrication, or rapid prototyping. In a general sense, we can define it as “a process of assembling materials to make objects or structures from a 3D data model, usually layer by layer, as opposed to traditional methods of production by subtraction” [GAR 11].

3D printing is a booming technology that is widely regarded as an industrial revolution. Thus, it is important to become familiar with some of the basic notions about 3D printing in general, the processes it utilizes, the way it works and its limitations.

Methods of design using 3D printing make it possible to shorten design and development times, improve collaboration between different parties and therefore help solve problems that arise between the worlds of engineering and design.

Although it has been used for a long time, especially for the production of prototypes, the term “3D printing” is now generally used to describe the additive fabrication method, regardless of the specific technology, material or application involved.

1.2.1.1. Main concepts

In additive fabrication, we can identify different manufacturing philosophies, with different methods and elements to use. All of these involve a series of steps in their design and rapid prototyping that form a specific cycle.

Generally, they consist of the choice of a material used as the basis for the construction of the model, as well as a sophisticated computer system that controls the processes of adding materials, such as depositing, sintering, injection, melting, etc.

Thus, the process begins with the creation of a 3D model in CAD (computer-aided design) format, which must be converted into STL (stereolithography) format. This format is processed by specific software programs, typically used in additive fabrication, which cuts the object into “slices” to create a new file containing the information for each layer.

This cycle of design and manufacturing can therefore be summarized in the following way:

• – digital modeling: creation of a 3D model, a true digital representation of what you would like to create. To do this, we will use CAD software. Additive fabrication is inextricably linked with the digital design of parts and structures;
• – exporting: generation of a file in a dedicated format (STL) containing all the geometrical information needed to represent the digital model;
• – stratification: conversion of the digital model into a list of com...