3D Concrete Printing - Technological issues in concrete mix design and extrusion

Transcription

1 3D Concrete Printing - Technological issues in concrete mix design and extrusion Technical visit to the National Institute of Standards and Technology (NIST) July 12th, 2017

2 3D Concrete Printing 3D Concrete Printing refers to the process used to synthesize a 3D model in successive layers of material to create an object, e.g. a concrete wall Robot-based 3D Printing Process: ATERIALS CONCRETE IXER CONCRETE PUP ROBOT CONTROL CONCRETE EXTRUSION REINFORCEENT DESIGN 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 2

3 ATERIALS Fresh concrete is the filament: Similar materials to that of concrete ax. particle size (1 to 4mm) Concrete admixtures aterial challenges: Pumpability vs. Buildability Concrete rheology (fresh state) 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 3

4 ATERIALS Concrete properties and mix design DTI s Test device (layer deformation) Stress 10Pa 1Pa Very-early age properties Hardening Setting 100kPa ~10kPa Thixotropy Yield stress t = 0 t = few minutes Time (t) Cement hydration and cement types Concrete admixtures (retarders and accelerators) Strength development and drying shrinkage Current challenges being addressed: mix design that enables to balance concrete pumpability and buildability expected product performance is affected by the process, thus online monitoring is a necessary 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 4

5 ATERIALS Buildability of fresh concrete (test without accelerators) Printing parameters - layer height: 10mm, layer width: 40mm, variable print speed 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 5

6 CONCRETE IXER Batch process: Concrete composition is constant Fresh-state properties can be adjusted by adding admixtures while printing Continuous mixing: Concrete composition is adjustable Fresh and hardened-state properties can be adjusted while printing Source: Tec Source: Tec ixing plant at DTI s Concrete Centre Source: BH Systems 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 6

7 CONCRETE IXER Feedback system in a continuous mixing production process: Production phase Pumping phase Printing phase Increase robustness of the production process Enable the production of functionally-graded concrete elements Cement Aggregates Stage 1 Stage 2 Stage 3 Dry mix Wet mix Pump Stage 4 Nozzle Funtionally-graded concrete sample Source: IT 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 7

8 CONCRETE PUP Peristaltic concrete pump: Pulsating extrusion Poor controllability Large equipment for initial tests Progressive cavity pump: Controlled extrusion (rotor-stator) Suitable for high-viscosity materials Source: PC 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 8

9 CONCRETE PUP Progressive cavity pump 3D Printed prototype DTI s progressive cavity pump Current challenge: Increase controlability and reliability of the printing process Production phase Pumping phase Printing phase Stage 4 Nozzle Cement Aggregates Stage 1 Stage 2 Stage 3 Dry mix Wet mix Pump 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 9

10 CONCRETE EXTRUSION Passive robot nozzle: The extrusion is controlled by a pump and the robot nozzle works as a dispenser that defines the shape of the printed layers. Active robot nozzle: The extrusion is controlled at the nozzle by a pump, enabling great precision and addition of admixtures during extrusion. Source: Total Kustom 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 10

11 CONCRETE EXTRUSION Nozzle experiments (3D Printed Nozzles) 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 11

12 3D Concrete Printing ATERIALS CONCRETE IXER CONCRETE PUP ROBOT CONTROL CONCRETE EXTRUSION REINFORCEENT DESIGN VERY-EARLY AGE PROPERTIES ROBUSTNESS FEEDBACK SYSTE RELIABILITY AWARENESS (SAFETY) ROBUSTNESS & PRECISION TRANSVERSAL REINFORCEENT TECHNICAL STANDARDS RETHINK DESIGN ETHODS 3D CONCRETE PRINTING INTERDISCIPLINARITY 3D Concrete Printing - from material design to concrete extrusion Danish Technological Institute 12

13 Thank you for your attention! Reference to this presentation: Leal da Silva, W.R. (2017). 3D Concrete Printing - Technological issues in concrete mix design and extrusion. [Presentation Slides] Retrieved from Danish Technological Institute website: Wilson Ricardo Leal da Silva Consultant, Civil Engineer, Ph.D. Concrete Centre obile wrls@teknologisk.dk Danish Technological Institute