Can 3D-printed concrete set new standards in housebuilding?

Concrete has been used in construction for thousands of years, from Assyrian aqueducts to floors in ancient Greece. The Colosseum and Pantheon served as early showcases of concrete’s potential, yet it has always been a challenging material to work with. This is because it requires moulds to adopt its final form, offering limited scope for sculpting or shaping. Its widespread adoption in post-war British housebuilding saw it quickly fall from grace, as it experienced structural failures and became associated with unattractive and poorly built high-rise housing. Today, concrete tends to be used for floors and foundations rather than visible external finishes. It can be used for load-bearing walls, but as it is weak in tension, it must be reinforced with steel (rebar) to absorb tensile forces and avoid structural failure. Concrete is also a major source of carbon dioxide, generating about 8% of all emissions globally (‘Concrete foundations for net zero’, Ingenia 102).

These longstanding challenges have opened the door to new approaches, particularly 3D-printed concrete. As a construction method, 3D printing concrete uses automated, computer controlled machines to build structures by extruding a specially formulated concrete mix in layers. Instead of relying on traditional formwork, the printer follows a digital design to place material precisely where it is needed. Not only is this more efficient and sustainable, but it allows for the creation of complex shapes that would be difficult or costly to achieve using conventional techniques.

A malleable yet solid material

Compared to poured or moulded concrete, 3D-printed concrete can reduce construction waste by up to 60%, production time by 70% and labour costs by 80%, demonstrated in 3D printing projects carried out in Australia by manufacturer Luyten. These savings could be transformative for a housebuilding industry with ambitious national completion targets to meet, just as prefabrication techniques revolutionised post-war residential construction. Professor Paul Shepherd, of the University of Bath’s Department of Architecture and Civil Engineering, explains: “When 3D printing, you can easily put material only where it’s needed.”

Shepherd has been instrumental in the university’s Automating Concrete Construction project (ACORN). This aims to make concrete construction much more sustainable and efficient, to address the fact that many concrete parts in buildings use more material than needed because they’re made with old, flat moulds. For example, it has 3D printed load-bearing floors using a quarter of the volume of concrete that would be required to support the same load using a traditional solid-slab, mould-poured floor.

The idea of spraying concrete through printer nozzles might seem odd, but as Shepherd explains, concrete can be held in liquid form for just long enough to be sufficiently malleable. “Materials need to be liquid enough to flow through the printer, while setting quickly enough to support the weight of the next layer when it is printed on top. Chemical additives include retarders, which delay the setting period of the concrete and makes sure it stays liquid while waiting to be printed, and accelerators to speed up the setting process once it’s output. There is a lot of research being done to optimise the concrete mix for 3D printing, including investigations into whether new materials such as nanoparticles and graphene can help.”

Another way is modifying the material properties between layers to gradually change the microstructure and makeup. “Changing the proportions of cement and aggregate allows different material stiffnesses and strengths to match requirements in different parts of the structure,” adds Shepherd. “This is known as ‘functionally graded’ material.”

The precise composition of concrete has varied enormously over the centuries, so this isn’t anything new – but the ability to have different mixes in different parts of the same structure is. However, 3D printing is introducing new challenges in construction projects. “Concrete is great in compression but poor at resisting tension,” explains Shepherd. “In ACORN, we tackled this by using geometry – our floors were vaulted, like a gothic cathedral roof or an arch bridge, so that almost all of the material was in compression. But since structures need to withstand different loads like horizontal wind or vertical snow, some sort of reinforcement is generally needed using a material that is good at resisting tension.

Traditional floors use steel reinforcement meshes, but ACORN used short glass-fibre strands added into the concrete mix just before printing.” These are applied in situ rather than installed separately, as reinforcement meshes are. It is a simpler process and their ratios can be optimised for greater efficiency and strength. The challenge of providing 3D-printed concrete structures with the required strength is ongoing, according to Shepherd. ACORN tested the robotic placement of carbon fibre tapes but chopped glass fibre proved to be a simpler solution. 

While ACORN didn’t need to print temporary support for concrete during printing, another project that Shepherd was involved in did. He was part of a team of researchers from Imperial College London and University College London that used a swarm of several drones to create large 3D-printed structures made of foam or cement. Taking inspiration from nature, the drones worked together – with one or two builder drones equipped with a 3D printer flying in circles while depositing the material to build up the structures one layer at a time, while another used a depth-sensing camera to develop a 3D map of the structure as it progressed. This technique could help construct tall or complex buildings and structures, without relying on support scaffolding or heavy construction equipment.

Scaling up 3D printing

While 3D-printed concrete has proved to be efficient, conventional industrial 3D printers would clearly be inadequate for construction work, as they are far too small. Manufacturer Luyten was founded to address the need for purpose-built construction robots as opposed to repurposed ones, as traditionally used in 3D concrete printing.

The company started out manufacturing printers to use in academia, which permitted controlled experimentation with printable cementitious materials and has now developed gantry and crane-based systems that can undertake full-scale residential construction. The company’s X12 printer can be assembled on site in just 20 minutes using standard hand tools, and can print structures up to 6 metres high and 12 metres wide, as well as producing varying object lengths, which could theoretically enable a whole terrace of houses to be constructed. Designs are typically modelled in BIM (building information modelling) or CAD (computer-aided design), before being imported to the printer using three-dimensional surface geometry file formats such as STL, a widely used file format for 3D printing and CAD that represents 3D object surfaces using a mesh of triangles.

Before launch, Luyten’s printers are subjected to extended continuous and cyclic loading, repeated calibration and intentional de-calibration sequences to test their positional recovery and robustness. They are tested across temperature gradients with varying humidity and moisture regimes to determine their restart behaviour, fault tolerance and controlled degradation. According to the company’s CEO Ahmed Mahil, “reliability in construction is defined as much by predictable recovery as by nominal precision.”

Making a judgement call

Controlling a 3D printer is a hugely complex task, particularly in unpredictable real-world conditions. Mahil explains that human oversight remains crucial to effective deployment: “Luyten’s control software is developed in-house to address the distinctive demands of construction-scale additive manufacturing. The software provides real-time monitoring of key operational parameters, including motion stability, extrusion consistency, and system status across the full build envelope. This monitoring capability is not passive; it is designed to inform operator decision-making as conditions evolve on site.”

Operators use an interactive control panel to adjust print speed, extrusion rate, offsets and recovery protocols in real time. They can also respond to field variables and manage pauses or restarts without compromising structural continuity. Unlike small-format printers or lightweight robotic arms, construction-scale printing operates within open, variable environments where informed human judgement remains essential. “The emphasis is on operator authority and adaptability, enabling intelligent intervention grounded in engineering understanding,” Mahil adds.

Despite recent rapid developments in AI software, Luyten uses it in an assistive capacity rather than granting it decision-making autonomy. AI-enabled tools are used to monitor print consistency, analyse sensor data related to material flow and motion stability, and support quality assurance and predictive maintenance. Human oversight is maintained for all structurally consequential decisions.

3D printing concrete on site and off site

There are clear differences between on-site and off-site printing – and benefits to both. While the former underpins ground-up construction projects, off-site modular printing can be used to preprint complex shapes for assembly later. Central to ACORN’s plans is building concrete components off site using automation and robotics to create better-shaped moulds. This allows beams, columns and floors to use only the material needed, reducing waste and emissions. “Off-site allows better quality control of the finished products, plus easy waste recovery, which can be reintegrated into the manufacturing process,” says Shepherd. “Off-site also means faster construction times on site, since the site becomes a place to assemble rather than manufacture. Some parts of buildings are being delivered to site with all the plumbing, electrics and interior decorations already in place.” This couldn’t be done with concrete poured on site, extending a benefit to concrete construction already associated with other prefabricated building methods.

While off-site concrete printing has its advantages, Shepherd acknowledges that there are limitations. “Off-site requires the parts to be transported from factory to the site. This puts limits on the size of each part, so a design that necessitates a large all-in-one concrete pour would need significant redesign if it were to be made off site.”

However, the divide between on- and off-site doesn’t have to be binary, as Shepherd points out. “Some projects have used a concrete 3D printer inside a shipping container, delivered to site so the parts could be made locally and then assembled. Others have lorry-based 3D printers that drive to site and 3D print in situ.”

The future of construction?

3D concrete printing is an area where Shepherd sees potential, once significant barriers are overcome: “We can already design complex shapes and render them physical, either by laying down layers of concrete one on top of another, or by spraying concrete onto a shaped mould. Getting tension-resisting reinforcement into those complex shapes is more of a challenge, so I believe the win-win comes when we optimise the shapes to minimise their need for reinforcement – using concrete for what it is good for, by resisting compression.” However, he says that, like any new technology, in the short term 3D concrete printing will need to fit into an existing design process, legal framework and supply chain that was not created with it in mind. “More insights are needed into the structural performance of 3D-printed concrete, not least its long-term fatigue behaviour, and its ability to resist earthquakes and fire. This is an area I am keen to explore as part of my ongoing research.”

Construction has lagged behind other engineering disciplines in the adoption of automation and targeted printing. While the need for minimising material usage has driven huge efficiencies in aerospace manufacture, the buildings and construction sector still accounts for 37% of global greenhouse gas emissions, according to the UN Environment Programme. Using concrete more sparingly (and efficiently) could play a significant role in the pursuit of net zero targets around the world, as well as bringing construction in line with more efficient manufacturing sectors.