3D Printing for Construction with Alternative Materials

Industry 4.0 has pushed construction to adopt processes that optimize the manufacturing of customizable solutions. Prefabrication, is beginning to understand that 3D Printing (3DP) with cementitious materials may open a new and wide range of options both formal and chromatic in customization, avoiding complex formworks, reducing costs and manufacturing time. Certified products are demanded, but it is obvious that there is a growing desire for tailor-made façade solutions, especially in its plasticity. Façades with designs, colors, and textures may thus overcome the execution constraints, narrowing the manufacturing process to the architectural conception and design process. In 3D printing, design process and its fabrication are engaged, enabling a great formal freedom and precision in the information transfer from drawing to its construction. The creative process is directly linked to the constructive process, bringing design closer to its materialization. Matter responds to form and form is designed by the matter capacity. This technology thus seems to be the ideal solution for the audacious design forms yet optimizing the constructive process.

A fundamental modification of the construction is occurring with the adoption of processes digitalization. In the construction field, quality is often associated with cost, making the use of advanced materials not competitive with the most basic concrete. On the other hand, as the standard specifications increase with time to sustain safety issues or customer needs, construction has never been more complex. This complexity is nowadays highlighted by the multiplication of the layers, one for each request for thermic or acoustic insulation which makes the concrete part of the total cost less and less significant. In this environment, digital construction should not aim to replace precast elements but rather bring functionality to the matter, such as insulation, leading to a reduction in the trend of the addition of layers and therefore leading to a significant reduction of the cost. Moreover, the decrease in the total amount of material used will have a higher environmental impact than a substitution of concrete for so-called greener products. Currently limited by its cost when compared the traditional construction methods, the improvement of the technology from the robotic to the software will lead to a competitive technology for specific elements such as façade elements or structural columns. As the cost of 3D printed elements is independent of their complexity, as moulds are not required, digital construction allows architects to develop new ideas or to bring back brilliant ideas from past forgotten for economical reasons. To allow this revolution to occur, chemists, architects, engineers, and software developers must work together to overcome the challenges facing digital construction.

Magically attracted by the sparks of his father’s grinder, Massimo Moretti grows up in the small mechanical laboratory at home and he delights in building works to aggregate his peers. He graduated in 1974 as an electronic technician and he started developing products. Massimo Moretti collaborates with Research Centers, Universities, R&D Departments, big national and international companies to create industrial automation projects, 3D modeling and prototyping not only in the field of mechanics but also in the interior design, cosmetics and chemistry fields. In his first 30 years of activity, he filed for about twenty patents before moving to open source and to the creative commons. His way of working is identified by invention and innovation. In his research path, essential for the product development, he has been approaching 3D printing since 2000. In 2012, together with a group of young designers, he founded WASP (World’s Advanced Saving Project), a company that designs, produces and sells 3D printers Made in Italy all over the world. Massimo Moretti, taking inspiration from nature and from the observation of the Potter Wasp, which builds its own nest with material recovered from the surrounding environment, moves WASP to produce large 3D printers able to build houses with natural materials and available on the territory, at a cost tending to zero.

Additive manufacturing (AM) is a core technology on the paradigm shift to Industry 4.0 and has already impacted health, aerospace, automobile, military, fashion fields, and, more recently, construction. The most widespread AM method in the construction industry is 3D cementitious material printing (3DPCC). The main advantage is the freeform architectural design without formworks needed. Increased productivity, reduced costs, more safety worksites are potentially expected, and environmental benefits within materials savings and waste generation reduction. The freeform architecture and precision material placement make 3D printing particularly exciting for architectonic purposes, such as structures, buildings or elements. From the perspective of materials science, 3DPCC mix-proportioning remains one of the most critical aspects due to (i) the very demanding requirements, namely at fresh state; (ii) the needing of several constituent materials; (iii) the sensitivity of the mixtures to natural variations. The current work aims to add insight into the mixture design and assessment of architectonic 3PPCC through cooperation between science and industry. Employing locally available materials, establishing a rational basis for preparing and designing 3DPCC, applying novel testing procedures, providing understandings, and certifying its behaviour are fundamental questions. Thus a mix compositions study was accomplished, using locally available materials in Turkey, namely, white Portland cement and metakaolin. A systematic choice of fresh state parameters and identification of their threshold values to achieve printable mixtures, such as flow table and Casagrande, was established. Afterwards, the optimal mixture was employed to print architectonic objects, and additional tests were performed on samples. This works aimed to contribute to 3D printing as a way for the paradigm shift to Industry 4.0 and stimulate the adoption of clean and environmentally sound technologies and industrial processes in the Construction Sector. Besides, a straight collaboration among the scientific community and industry is essential to make 3D printing a more practical, cost-effective, eco-efficient and widely accepted technology.

Sustainable materials and additive manufacturing have the potential to increase material efficiency and minimize waste in the building process. One of the most promising materials is salt (sodium chloride). It is highly available as a residue of desalination and potash production processes and attracts attention due to its material properties (storage of humidity and heat). This research presents an investigation and evaluation of using salt as an alternative material in additive manufacturing. Thus, the focus of the study was on small-scale 3D printing with paste extrusion. Experimental studies of different salt mixtures with different binders, printing properties and other parameters were analyzed in three stages. In the first phase (P1) the mixing ratio of salt and potential binders (clay, gypsum, cement and starch) was defined; in the phase two (P2) the most promising mixture was selected, modified by additives and investigated by 3D image scan measurements; and in the last third phase (P3) the potential applications of salt in additive manufacturing were presented. As the research shows, the salt in material extrusion processes can substitute the main material by up to 70%, is successfully manipulated with different additives (to improve the workability of the printing mortar) and is highly dependent on the printer`s settings. For future full-scale 3D printing with salt many steps still have to be taken. However, incorporating salt in additive manufacturing showed a potential of saving material resources, addressing environmental issues and initiating new construction processes.

3D printing (3DP) is an example of a sustainable technology capable of replacing traditional manufacturing processes. One of its advantages is the use of optimized production processes, even for customized products, as well as the almost non-existence of waste. 3DP mortars (3DPM), therefore, rely heavily on Portland cement (PC), a material with high carbon emissions and energy consumption related to its manufacture. In order to comply with the growing environmental regulations and concerns, it is imperative that its use becomes more moderate and, as such, alternatives to PC or additives to reduce its percentage are being sought. At the Faculty of Engineering of University of Porto, research has been conducted to produce 3DPM with different waste materials. This study has the following objectives: (i) reduce PC by adding sugarcane bagasse ash (SCBA), with a strong emphasis on performance; (ii) substitute natural sand with recycled brick sand (RBS), aiming at replacing a natural aggregate while exploring new aesthetic possibilities. As to assess their viability as 3DPM, several mortars with different amounts of SCBA and RBS were formulated, taking into account some of its fresh and hardened properties as well as exploring different colours and textures. In the end, the best compositions were printed using material extrusion equipment.

4D Printing is the combination of traditional additive processes with smart materials and external stimuli. This combination guarantees the printed parts the ability to transform themselves over time, which could be, for example, self-sensitive, self-assembly, or self-healing. These skills can be of great interest for modern constructions, as the world is demanding autonomous structures, with low energy consumption and environmental impacts. In this sense, this study sought to analyze the movements of 4D printing in civil construction and architecture to understand how close, or distant, this technology is to the reality of these sectors. Results show that the 4D stage in these applications is still very embryonic and limited at laboratory scale. However, there is potential for the future, if major challenges such as the production of large parts and, mainly, the control of the transformations of the components produced and the external stimuli applied are overcome.