A team at the Massachusetts Institute of Technology has developed a new way to 3D print concrete structures, a technique that could simultaneously cut material use, costs and climate-damaging CO2 emissions. While 3D-printed concrete structures are already available in the world, current systems are not very optimized. However, previous attempts at adaptation have suffered from being too perfect. That is, the blueprints generated by the algorithm were for ideal conditions that real-world, slightly clunky printers could never actually create. The MIT team has developed a new algorithm, based on more sophisticated mathematics, that can take ambiguity into account when finding a realistically ideal design. Their first result is a model bridge that is 16% lighter than its conventionally built counterpart with the same load capacity.
This matters, because humanity certainly uses a lot of concrete. As, except for water, we use concrete more than any other substance on Earth. But to solidify all that, huge amounts of CO2 are pumped into the atmosphere: 8% of all CO2 emissionsIn fact, come from this process alone. Therefore any reduction in CO2 production from concrete production would be a major step forward in the fight against climate change. Earlier research indicated that 3D printing concrete saved 86% emissions compared to the traditional process. And that’s to say nothing of material savings! Low resources, low cost, low weight, low carbon. Of course I like it. A major barrier to widespread adoption has been the gap between the ideal design and the actual printer. If this new method can bridge the gap, it opens up some very exciting possibilities.
The new method incorporates the underlying mathematics of the programs that create blueprints. As mentioned in the team white paper and reported by MIT NewsOlder models could not easily capture printer imperfections, resulting in very imprecise designs. The printer has limitations such as the size of the concrete beads it lays down, the bend radius of the nozzle, and the curvature (or lack thereof) of the beads’ lines. Particularly sharp angles are not something printers are very good at. To capture all that in numbers, there is a mathematical technique called mixed-integer programming that could work, but it is so computationally intensive that it was not possible. What changed, and what the MIT team brought to the table concretely, were some recent innovations in the way this technique was calculated. There’s quite a bit of smart wizardry here, but the end result is that it’s now possible to produce optimal designs based on what a printer can actually produce.
Custom concrete design to order
There’s a lot to like here, but it just gets better. Traditionally, once concrete is made, it has to be poured into a mold. Mold making is a non-trivial process in itself, and forces the finished product into a particular shape. What if you want to make a quick change in size? Or what if you only want to make a complex shape once, for which making a complete mold would be uneconomical? There is no need for this with 3D printing, as it is simply laying down concrete beads from a nozzle. Create any crazy shapes you want, make changes instantly, do whatever you want. Again, while saving on resources, costs and emissions.
But we haven’t yet reached a golden (or, well, dull) new age. More testing needs to be done, and this methodology needs to be scaled up. The test bridge was less than 8 feet long and weighed only 900 pounds. The actual infrastructure will be slightly higher than this. Also, pure concrete has limitations in terms of the direction of the applied force; From one direction, it is a mighty bridge, but from the other direction, it is a fragile little snowflake that breaks easily. (In fact, the test bridge broke when someone tried to lift it.) This is why real-world concrete is reinforced with rebar. And no amount of fancy math has figured out how to 3D print rebar, or even how to manually add rebar to the 3D printing process. Still, this is real and exciting progress.
