Digital Fabrication with Cement-Based Materials: State-of-the-Art Report of the RILEM TC 276-DFC (RILEM State-of-the-Art Reports, 36)

This book presents the work of the RILEM Technical Committee 276-DFC: Digital fabrication with cement-based materials. The most important outcomes of the technical committee are presented. First, a unified process classification for digital fabrication with concrete is proposed, discussed and illustrated. Then, a state of the art of the testing methods (both at a material and structural level and in the fresh and hardened state) is provided. The gathered knowledge is expected to form the foundation of some quality control procedures for fresh properties along with hardened properties and service life performance. The book will benefit academics, practitioners, industry and standardization committees interested in digital fabrication with cement-based materials. Committee RILEM Publications Contents 1 Digital Fabrication with Cement-Based Materials—The Rilem D.F.C. Technical Committee History, Strategy and Achievements 1.1 Background 1.2 The Expected Benefits of Digital Fabrication with Concrete 1.3 Obstacles 1.4 RILEM Technical Committee Creation and Scientific Strategy 1.5 Achievements and Today’s Status References 2 Digital Fabrication with Cement-Based Materials: Process Classification and Case Studies 2.1 Introduction 2.2 Assembly and Material Forming Processes 2.3 Classification of DFC Processes 2.4 Case Studies 2.4.1 Printing and Assembling a 6.5 m Bicycle Bridge 2.4.2 Manufacturing Double-Curved Panels with Conformal Voids 2.4.3 The ‘BOD’: A 49 m2 Office Building 2.4.4 Shotcrete Printing a Reinforced Double-Curved Concrete Wall 2.4.5 Enabling Weight Reduction of a 12 m Footbridge 2.4.6 Column and Beam Manufacture 2.4.7 Commercial Panel Manufacture Using Flexible Moulds 2.4.8 In-Situ Production of Full Scale, Reinforced Concrete Walls 2.5 Summary and Outlook References 3 Digital Fabrication with Cement-Based Materials: Underlying Physics 3.1 Introduction 3.2 Fabrication Approaches, Processing Steps and Related Physics 3.3 Gravitational Flow and Capillary Flow 3.3.1 Gravitational Flow 3.3.2 Gravitational Flow in Combination with Vibration 3.3.3 Gravitational Flow in a Porous Medium 3.3.4 Wetting and Capillary Flow 3.4 Pumping and Extrusion 3.4.1 Predicting Pumping Behaviour 3.4.2 Ram Extrusion 3.4.3 Screw Extrusion 3.5 Mixing After Adding Accelerator in the Print-Head/nozzle 3.6 Load Bearing and Deformation Behaviour After Deposition 3.6.1 Acting Loads 3.6.2 Structural Failure 3.6.3 Deformation Behaviour 3.7 Physical Properties and Their Evolving in Time 3.7.1 Viscosity 3.7.2 Yield Stress 3.7.3 Thixotropy Parameter/Rate of Structural Build-Up/Structural Breakdown 3.7.4 Visco-Elastic Behavior, Modulus of Elasticity and Creep Coefficient 3.7.5 Surface Tension and Friction 3.8 Comments on Physically-Based Optimization Strategies 3.8.1 Example 1: Duality of (Balance Between) Easy Delivery to the Printhead and Shape Stability upon Deposition 3.8.2 Example 2: Setting Material Deposition Intervals Depending on the Rate of Structural Build-Up 3.9 Further Relevant Processes and Mechanisms 3.9.1 Weak Bond Strength Between Successive Layers in Extrusion-Based Additive Manufacturing: The Importance of Drying 3.9.2 Powder Bed: Application of Dry Particle Layers in Particle-Bed Binding 3.9.3 Pneumatic Transport of Dry Mix 3.9.4 Wet and Dry Spraying 3.9.5 Mould Filling (3D-Printed Mould, Integrated Formwork, Etc.) 3.9.6 Filling of Mesh Mold 3.10 Summary and Conclusions Appendix 1: Glossary of Basic Rheology Appendix 2: List of Symbols and Abbreviations References 4 Printable Cement-Based Materials: Fresh Properties Measurements and Control 4.1 Introduction 4.2 Process Rheological Requirements 4.2.1 Competing Stresses During Printing 4.2.2 Object Stability and Geometry Control 4.3 Background Chemistry and Chemical Admixtures 4.3.1 Flocculation (Thixotropy) 4.3.2 Hydration 4.3.3 Chemical Admixture Control—Set-On-Demand 4.4 Measurement Methods 4.4.1 Existing Measurement Methods 4.4.2 Methods Utilised or Developed for Digital Fabrication with Concrete 4.5 Indirect Methods: Calorimetry 4.6 Robustness and Quality Control 4.7 Summary References 5 Properties and Testing of Printed Cement-Based Materials in Hardened State 5.1 Introduction 5.2 Additive Manufacturing: Challenges and Pitfalls 5.2.1 Anisotropy: Occurrence and Influencing Factors 5.2.2 Interlayer Time Interval 5.2.3 Print Process Parameters 5.2.4 Mix Composition 5.2.5 Addition of Fibre 5.2.6 Distinct Casting of Layers 5.3 Sampling and Quality Control 5.4 Mechanical Performance of 3D Printed Specimens 5.4.1 Measurements 5.4.2 Compressive Strength 5.4.3 Flexural Strength 5.4.4 Tensile Strength (Inter-Layer Bonding Strength) 5.5 Durability and Transport Mechanisms in 3D Printed Materials 5.5.1 Fire Resistance 5.5.2 Transport Mechanisms 5.5.3 Pore Structure and Porosity 5.5.4 Air Voids 5.5.5 Carbonation and Corrosion 5.5.6 Freeze–Thaw Resistance 5.6 Recommendations References 6 Structural Design and Testing of Digitally Manufactured Concrete Structures 6.1 Introduction 6.1.1 Material & Process 6.1.2 Calculation Input 6.1.3 Design Aspects 6.2 Catalogue of Digital Fabrication Processes to Manufacture Concrete Structures 6.2.1 Structural Systems 6.2.2 Classification of Reinforcing Strategies 6.2.3 Strategies to Fabricate Concrete Structures 6.3 Fibre Reinforcement in Digitally Fabricated Concrete 6.4 Design Principles and Modelling 6.4.1 Approach to Anisotropy 6.4.2 Models and Load-Bearing Capacity 6.4.3 Structural Optimization 6.5 Structural Testing and Validation 6.6 Conclusions References