3D construction printing promises to revolutionize building by enabling rapid automated fabrication of architectural structures and components. But identifying optimal materials that balance printability, strength, and functionality remains an ongoing research challenge. For 3D printing to scale successfully for mainstream construction, printers must be able to reliably extrude ultra-durable materials onsite into super-strong finished components. This article analyzes the toughest and most resilient materials being evaluated for large-scale additive manufacturing of buildings and infrastructure.
Overview of 3D Construction Printing
Also known as additive manufacturing, 3D construction printing works by precision depositing successive layers of material based on a digital model to construct real-world structures and objects. Key process steps include:
- Designing a 3D architectural model with CAD software
- Slicing it into 2D layers and generating toolpaths
- Having the 3D printer precisely extrude material like concrete or polymers layer-by-layer
- Inserting rebar reinforcement between layers during printing
- Curing materials after deposition
- Assembling printed components into the final building
Materials are deposited by gantry-mounted extruders or robotic arms guided by the digital model. This enables automating fabrication of customized designs rapidly onsite.
Desired Material Properties
Ideally, print materials for construction exhibit these key properties:
- High strength – Strong enough for structural integrity and safety
- Stiffness – Resistance to deformation under loads
- Durability – Long-lasting performance over decades
- Workability – Flows through print nozzle and bonds between layers
- Cure rate – Hardens quickly after deposition
- Dimensional stability – Low shrinkage and creep
- Weathering – Resilience to environmental factors like moisture and UV
Achieving the optimal balance of these properties allows functional printing of super-strong finished components.
Categories of Printable Construction Materials
Major material categories under evaluation include:
- Concrete – Most common currently. Can customize mixtures.
- Polymers – Plastics like PLA, ABS, polycarbonate.
- Composites – Particle, fiber, or foil-reinforced concretes or polymers.
- Geopolymers – Cement alternatives using industrial waste or natural minerals.
- Metals – Steel, aluminum, titanium or alloys.
- Ceramics – Printed clay, sand, or cementitious mixes.
- Wood – Biomaterials like sawdust, mycelium, paper composites.
- Smart materials – Concrete or polymers with sensors or self-healing properties.
Different properties suit certain printing applications and construction challenges.
Top Contenders for Toughest Printed Material
Leading ultra-strong candidates include:
Steel Fiber Reinforced Concrete (SFRC)
- Steel microfibers added to concrete mix
- Greatly increases tensile and flexural strength
- More ductile with improved crack control
- Fibers well distributed throughout material
Macro Polynthetic Fiber Reinforced Concrete
- Larger polymer fibers like PVA or PE
- Amplify durability, ductility, impact resistance
- Reduce shrinkage cracking
- Alternative to steel fibers
Ultra-High Performance Concrete (UHPC)
- Low water, high cement, silica fume, steel fibers
- Very high compressive strength over 22,000 psi
- Reduced porosity and permeability
- Excels in strength, stiffness, and durability
- No Portland cement. Activated industrial waste or natural minerals
- Excellent adhesion results in high strength
- Sustainable alternative to traditional concrete
- Can reinforce with composites like graphene
Key Test Metrics
To compare material performance, standard lab tests characterize:
|Compressive strength||ASTM C39||Stress at failure|
|Tensile strength||ASTM C307||Peak stress and strain|
|Flexural strength||ASTM C78||Modulus of rupture|
|Fracture energy||RILEM method||Work to propagate crack|
|Bond strength||Slant shear test||Stress to debond layers|
|Abrasion resistance||ASTM C944||Volume loss|
|Shrinkage||ASTM C596||Strain over time|
|Creep||ASTM C512||Deformation under sustained load|
Compressive strength is the ability of a material to resist crushing forces. It is tested by applying a compressive load to a cylindrical specimen until it fails. The compressive strength is calculated as the load divided by the cross-sectional area of the specimen.
Tensile strength is the ability of a material to resist pulling forces. It is tested by applying a tensile load to a dogbone-shaped specimen until it fails. The tensile strength is calculated as the load divided by the cross-sectional area of the specimen at the point of failure.
Flexural strength is the ability of a material to resist bending forces. It is tested by placing a beam specimen on two supports and applying a load at the center of the beam until it fails. The flexural strength is calculated as the load multiplied by the distance between the supports divided by the moment of inertia of the beam cross-section.
Fracture energy is the amount of energy required to propagate a crack in a material. It is tested by pre-cracking a specimen and then applying a load until the crack propagates. The fracture energy is calculated as the area under the load-deformation curve.
Bond strength is the ability of two materials to adhere to each other. It is tested by bonding two specimens together and then applying a load to the specimens until they debond. The bond strength is calculated as the load divided by the bonded area.
Abrasion resistance is the ability of a material to resist wear and tear. It is tested by subjecting a specimen to a stream of abrasive particles. The abrasion resistance is calculated as the volume loss of the specimen divided by the mass of the specimen.
Shrinkage is the reduction in volume of a material over time. It is tested by measuring the change in length of a specimen over time. The shrinkage is calculated as the change in length divided by the original length.
Creep is the deformation of a material under sustained load. It is tested by applying a load to a specimen and measuring the deformation over time. The creep is calculated as the deformation divided by the original length.
A promising recent advancement is reinforcing various matrices with graphene:
- Graphene – nanomaterial with exceptional mechanical, thermal, electrical properties
- Graphene oxide (GO) – precursor for dispersions
- Graphene nanoplatelets (GNP) – layered GO particles
- Graphene fibers (GF) – spun into structural reinforcing elements
When incorporated into concrete, polymers or geopolymers, graphene significantly amplifies properties:
- Increased strength, ductility and fracture toughness
- Reduced shrinkage, creep, and permeability
- Thermal management and damage sensing potential
Graphene-reinforced composites enable lighter, stronger, and smarter 3D printed building components.
Leading Toughest Printable Material Candidates
Based on current research, top contenders for strongest printed materials include:
|Steel fiber reinforced UHPC||Optimized gradation of steel microfibers||Highest strength and ductility combination|
|Macro synthetic fiber reinforced concrete||Larger polymer fibers for durability||Excellent mechanical properties|
|Graphene-modified geopolymer||Nanoplatelets reinforce geopolymer binder||High strength with flexibility|
|Long carbon nanotube reinforced concrete||Long tangled carbon nanotubes for strength||Very high tensile capacity|
|Hybrid steel-polyethylene fiber concrete||Synergistic blend of micro fiber types||Balanced strength and toughness|
|Ceramic-metallic composites||Dense printed ceramics with ductile metal||Damage tolerance and hardness|
Layering and locally tuning printable formulations unlocks next-level material performance.
In conclusion, the evolution of 3D construction printing is continuously advancing through innovative composite chemistries and reinforcement techniques. Among these, fiber reinforced concretes and graphene-enhanced composites are emerging as frontrunners, showing immense promise in fulfilling critical performance criteria. A notable achievement in this field is the successful demonstration by Printable Concrete of printing with graphene and carbon fiber reinforced concrete. This pioneering development is a testament to the ongoing efforts in material innovation and testing, bringing us closer to discovering even more resilient printable formulations. As we continue to customize mixes with advanced reinforcements and smart functionalities, we pave the way for building super-resilient structures and infrastructure that redefine the future of construction.