Development and Production of New and Tailored Particles for the Combined SPI and WAAM Process in Concrete 3DP
Funded by: DFG
Contact person: Leigh Duncan Hamilton
Summary of the overall project:
Additive manufacturing (3D-Printing, 3DP) in construction is an up-and-coming methodology to create a diverse palette of bionic-optimised components, thus, leading to cost efficient as well as material efficient structures. Furthermore, additive manufacturing methods are capable of producing free form structures without moulds or special tools. This results in a certain independence between production costs and complexity of the individual components.
he project at hand is funded by the DFG and part of the collaborative research centre “TRR 277 Additive Manufacturing in Construction (AMC)”. It involves a combination of the particle-bed based AM technology “Selective Cement Paste Intrusion (SPI)” and the simultaneous 3DP method “Wire and Arc Additive Manufacturing (WAAM)” as a means of reinforcement. Within SPI, an aggregate layer of sand is spread on a surface, followed by the local intrusion of the cement paste into the aggregate layer. These steps are repeated and the consequent hardening forms the structure. WAAM, on the other hand, uses arc welding to melt a metal wire in the correct positions, and thus, create a component layer-by-layer.
Figure 1: Production cycle of SPI with WAAM reinforcement
Consequently, the combination of SPI and WAAM is linked to obstacles that must be overcome in order to ensure an efficient process as well as fundamentally sound components. The most pronounced challenge is the occurrence of high temperatures (approx.. 1600 °C) during WAAM. As a result, the penetration behaviour of the cement paste and the subsequent strength of the concrete matrix are affected in a negative manner.
The main objective as a partner at iPAT is to create tailored particles for the combined process as a whole. This includes the adjustment of particle size distribution and morphology for the aggregate as well as the cement paste with dry operated various mills. Another important aspect is the mixing of additives into the aggregate bed. Thereby, the temperature distribution in particle beds and cooling effects of the additives will be investigated. Future steps also cover the variation of water content within the cement paste as well as the coating these of particles.
Figure 2: Left: Test rig for temperature distribution in particle-beds; Right: Heat propagation as a result of WAAM
Chair of Material Science and Testing as well and the Institute for Machine Tools and Industrial Management at the Technical University of Munich.