Networking with other projects

Poster

TRR277_A02_Poster_1-DFG-Begutachtung
TRR277_A02_Poster_2-DFG-Begutachtung

Selective paste intrusion (SPI) is a particle-bed-based additive manufacturing technology in which aggregates are spread in thin layers and bonded by cement paste. To qualify SPI for structural concrete elements, the inclusion of reinforcement is mandatory. The innovation introduced here is that reinforcement will be implemented simultaneously in the SPI process using Wire and Arc Additive Manufacturing (WAAM). Different active and passive cooling strategies, e.g. particle surface functionalization and the synthesis of new particles, will be developed to deal with the high temperatures during WAAM.

Objective

Combination of SPI and WAAM:

• 3D printable WAAM reinforcement with properties comparable to those of conventional rebars, validated through experiments and simulation
• Development of tailored particles for cooling and storing water for the combined SPI+WAAM process
• Optimized cement paste for enhanced temperatures

Approach

At the cbm, the Selective Paste Intrusion (SPI) is being researched. One research focus is the integration of reinforcement using Wire and Arc Additive Manufacturing (WAAM) during the printing process. Due to the temperature loads of the WAAM process, the system limits, such as the maximum temperature load in the SPI process, must first be quantified. From this, process parameters and strategies to reduce the temperatures are derived and also researched. Approaches here are the functionalization of the aggregates and optimization of the cement paste formulation to withstand higher temperatures. However, an increase in the distance between the particle-bed and the printer nozzles and active cooling of the WAAM process are strategies for reducing the temperature load. The aim is to combine the two individual processes, SPI and WAAM, into one process and produce a demonstrator.

The Institute for Particle Technology is conducting a closer inspection into developing tailored particles suitable for the hybrid process. On the one hand, an optimal combination of particle size distribution and morphology of the aggregate particles as well as cement paste are to be found to support the process. On the other hand, the effect of certain additives on both components are being studied to reduce or withstand the remaining thermal load. One approach involves integrating additional water into the aggregate bulk material and cement paste whilst maintaining sufficient material properties for SPI. Further studies will involve combining the aforementioned with binding accelerators to increase process speed.

At the iwb, suitable process parameters for the production of WAAM-manufactured reinforcement structures are identified and process investigations are conducted with an experimental setup. Thereby, the cooling behaviour of the manufactured reinforcement geometries is analysed using thermographic imaging. Based on this, the cause-effect relationships in WAAM of the steel reinforcement are quantified by regression analyses. Numerical process models are created to extend the understanding of the process. These models describe the temperature distribution in the WAAM-manufactured component and consider the influences of specifically cooled areas. Thus, a suitable cooling strategy can be derived theoretically and be validated, after integration into the experimental set-up.

Networking with other projects

• A01: Permanent exchange of the project status within the workgroup
• A03: Permanent exchange of the project status within the workgroup
• A04: Joint series of experiments for the investigation of temperature influences
• A05: Integration of reinforcement in the SPI process
• A07: Exchange of process and material parameters of the WAAM reinforcement
• A08: Exchange about nozzle technology and printer automation (pin roller)
• C01: Sending of material properties for model calibration
• C02: Sending of material properties for model calibration
• C04: Exchange of process parameters for BIM
• C06: Sending of an SPI printed test object for 3D-laser scanning test measurements

Networking with other projects

Poster

The gradation of material properties in concrete extrusion allows more efficient use of resources and multifunctional design of components, but represents a particular challenge in pump-based extrusion systems. Therefore, an innovative near-nozzle mixing system, called gradation ready extruding system (GRES), is being developed in A03 which enables immediate gradation of the material properties. This allows to locally extrude different materials ranging from normal to lightweight concrete. Furthermore, the short conveying distances for the fresh concrete facilitate the extrusion of e.g. more sustainable materials that cannot be processed in previous extrusion systems due to impeded workability compared to normal 3D printing materials. The combination of multi-material printing with an automated vertical rebar insertion strives for high performance as well as a precise adjustment of material properties to the local needs and thus for a more sustainable material use.

Aim

Graded Concrete Extrusion

• Design and construction of a gradation ready near-nozzle mixing system and its implementation on an industrial robot
• Development of discrete material gradation (with regard to thermal conductivity, strength, and sustainability)
• Integration of an automated vertical layer reinforcement
• Conception and production of a multi-material construction element

Approach

Experimental investigation and DEM-Simulation

• DEM Simulation for system function validation
• Experiment based development and optimization of process and materials for gradation
• Quantification and validation of material properties for graded concrete extrusion

Networking with other projects

• A02: Construction of a demonstrator combining the technologies
• A04: Collaboration on vertically inserted reinforcement using the same insertion device
• A05: Evaluation of suitable reinforcement strategies
• A08: Construction of a demonstrator combining the technologies
• B04: Collaboration on path planning as well as process and control parameters. Furthermore, collaboration on adaption of insertion device (together with A04)
• B05: Collaboration on extrusion of (lightweight) concrete, e.g. with regard to material development and supply, as well as on robot control
• C01: Thermal and geometrical optimization of a lightweight/graded concrete construction element
• C02: Collaboration on optimization of graded concrete elements; input for simulations
• C03: Thermal and geometrical optimization of a lightweight/graded concrete construction element
• C04: Input for BIM
• C05: Collaboration on dry joints and conception of joints between different AM technologies
• C06: Discussion on pre-fabrication and in-situ manufacturing
• C07: Exchange on requirements for standardization processes

She was an expert in additive manufacturing, rheological questions and material development. She organized the material development and material testing on behave of WG Gehlen.
She also was an expert in AM by extrusion of concrete, rheological questions and material development. She was responsible for all research regarding extrusion, material development and testing.