Often times, when planning the shape of concrete structures, Architects are forced to modify their creative designs due to the inability of current construction methods to bring their ideas to fruition.
Even in cases where construction is possible (Figure 1), complex formwork structures need to be set up by skilled labor (Figure 2), who run the risk of deviating slightly from the original design due to on- the-ground construction realities.
This case study therefore highlights an alternative method for fabricating complex concrete structures using Additive Manufacturing (AM) technology (a. k. a 3D printing). The method was used by Immensa Technology Labs, in collaboration with Consolidated Contracting Company (CCC) and BigRep Gmbh, to fabricate an intricately designed, smart concrete wall that would have been impossible to make using traditional construction methods (Figure 3) .
Current construction methods can be very linear. For example, when building the walls of a room, concrete blocks need to be laid first before the electrical wiring is done. Also, placing additional elements such as lights and switches in a concrete structure requires that portions of an already fabricated wall are drilled and cut- out to make way for the new structures. Such drilling and cutting tend to create areas of stress concentration in the structure and could reduce the load carrying capacity of the wall.
Furthermore, complex designs by architects are often difficult to achieve using these traditional methods, leading to a need for alternative methods of construction that enable the realization of more intricate and multi- functional concrete structures.
At Immensa Technology Labs we set out, together with Big Rep and Consolidated Contractors’ Company ( CCC), to fabricate a concrete wall that defied some of the challenges being faced in the construction industry today. The technical requirements for the wall are detailed below.
Wall Height: 2 meters
Wall Width: 0.88 meters
Wall Thickness: Variable
Density Distribution: Graded
30MPa Compressive Strength
Embedded Touch Sensor
Embedded Light System
Figure 1. Science Hills Museum, Japan: Wavy concrete roof that doubles as a grassy park.
Figure 2. Complex girder wall formwork system for wavy wall structure
Figure 3. Smart Concrete Wall, Dubai: Concrete wall with embedded sensors fabricated using 3D printed molds
We set out to use 3D printed molds as a tool for achieving the intended design and functional goals. The process adopted is illustrated in Figure 4 and would be described in detail below.
Figure 4: Process for fabricating complex concrete structures using 3D printed molds at Immensa Technology Labs
3D Design of Concrete Structure
Considering that 3D printing technology enables freedom of design, it was easy to generate a CAD file that met all the design requirements. The front, top, and side views of the designed concrete structure are shown in Figure 5.
Figure 5: Front, top, and side views of twisted, variably thick, density graded concrete structure
3D Design of Custom Molds and Complementary Structures
Based on the CAD file generated for the concrete structure, custom molds were designed. The molds are designed in such a way that they are easy to install. For this project, additional structures that complement the mold were also designed to enable easy installation of electrical cables, sensors, and led lights within the mold system. Figures 6 and 7 show the designed molds as well as some of the complementary structures.
Figure 6: Mold design and complementary structures for electrical cabling
Figure 7. Design of complementary structure for embedded sensor
3D Printing of Mold Structures
Once the design is finalized, they are sent to a 3D printer for fabrication. The type of printer and material used for each structure depends on its intended application. Most of the complementary structures were printed with Selective Laser Sintering ( SLS) technology whilst the molds themselves were fabricated using Fused Deposition Modelling ( FDM) machines.
Figure 8. 3D printing of mold panels
Assembly and Casting of 3D Printed Mold Structures
Assembly and casting of the mold structures were carried out concurrently. The touch sensor is embedded in the molds at this stage. Figure 9 shows the 3D printed molds at various stages of the assembly and casting process.
Figure 9. 3D printed molds during the assembly and casting process
Demolding and Electronics Installation
Once the concrete had set, the molds were removed and installation of LED lights started. As the electrical cables and capacitive sensor had already been installed during the casting process via the 3D printed complementary structures, the concrete structure did not have to be drilled or modified in order to complete the electronics installation.
The embedded sensor was also fine- tuned to respond to human touch, and transparent cases for covering the LEDs were 3D printed and installed.
A video showing the capacitive touch sensor in action can be found here
Figure 10. Demolded concrete structure undergoing final steps of electronics installation
The use of 3D printed molds for concrete casting is a practical alternative for construction companies and architects who want to buck the trend and bring into fruition concrete structures that were previously thought impossible to fabricate.
By integrating complementary 3D printed structures into the mold design, the structural integrity of the concrete structure can be maintained whilst achieving designs that were not possible before. Also, additional elements like lights, sensors, and electrical cables can be integrated within the structure, reducing the overall fabrication time and leading to the realization of multi- functional structures.
Figure 11. Variably thick, twisted “smart wall”