Can 3D printed hempcrete replace traditionally-used concrete?

Petros Sideris is an Assistant Professor in the Zachry Department of Civil & Environmental Engineering at Texas A&M University. He started looking into construction 3D printing as an alternative to traditional construction more than five years ago, and his research has focused on concrete 3D printed structures and how they perform under service conditions and extreme events such as earthquakes. He has not started researching the potential of 3D printed hempcrete.

Throughout his research in the broad area of concrete structures, Petros Sideris has conducted large-scale structural testing, computational modeling of structures, and modeling at the material level.

When he first heard of construction 3D printing, he was skeptical (considering this was more than five years ago). “I’m not saying that I thought it wouldn’t work. I’m saying that it wasn’t as popular. Interest in this area has been growing almost exponentially since then. And there has been this idea out since the 90s, right. There’s even some work we found online that was performed in the 30s.”

However, nearly a week later, he was sold on the idea. “I felt like there is a lot of potential in terms of automation. And if you look into this in more detail, you’ll see that the construction sector is probably the least automated sector of the economy, not only in the U.S. but worldwide. There’s a huge potential for automation there, and 3D printing was well in this direction. And then it ties in very well with efforts to address some major problems like, for example, the housing issue, the ‘housing crisis,’ as we call it in the U.S., which is also probably a problem in several countries. That’s kind of how I started. I saw value, and then I dived into that,” said Petros Sideris. “And here we are, with several different ideas, some of those relating to concrete and now some more recent ones that relate to more sustainable materials and their applications in actual large-scale construction.”

The big picture idea for Petros Sideris’ research is that there is an increasing need for housing in the U.S. and many countries around the world. In the U.S. alone, it has been recently estimated by the Federal Home Loan Mortgage Corporation (Freddie Mac) that the country needs more than 3.8 million new homes. At the same time, the manual labor force, the construction labor force, is decreasing. Considering this – it is highly unlikely that the current state of construction practices can address these needs.

This is where the need for automation and alternative construction techniques are of value. 3D printing, due to its automation, lights-out, 24/7 manufacturing, requiring minimal personnel, is a near-perfect solution to this problem.

However, using traditional materials in conjunction with this more contemporary technology is not ideal, as concrete, for example, is not a sustainable and environmentally-friendly material.

“Concrete, as you probably know, is not a very environmentally-friendly material. It comes with a lot of carbon emissions. So that’s a big issue. What our project is trying to do is to marry these two ideas. One is construction 3D printing, which I would say is a more environmentally-friendly construction process for two reasons – you do not need to place concrete anywhere else but at the locations where you need it, and you don’t need formwork, which you would usually use just a few times and then throw it away. So these are two major benefits of the process itself. Now we try to marry this process with a sustainable material. That sustainable material is hempcrete. Hemp by itself is a very attractive material to us in construction because it, essentially, has a negative carbon footprint – it sequesters a lot of CO2. What we’re trying to do in this project is print using hempcrete. That’s the big challenge.”

The second challenge is for the team to design structures that are structurally code compliant and also code compliant in terms of energy performance. “So we try to rethink how you design structures using this type of material. We will also be trying to end up with an entire structure that is net carbon negative over its service life.”

The team will also be looking at the structures’ performance over time. If a structure itself is sustainable, at face value, but needs to be replaced or repaired every few years due to hurricane damage, for example, then it is not truly sustainable. To prove the hypothesis, the team will have to find the harmonious balance between sustainability and resilience – and study how the two affect each other.

In terms of the process of turning the hemp plant into hempcrete, Petros Sideris noted that he is not a materials engineer, and he may not be the best person to explain the process to us, “But what I can tell you is that we’re looking at different parts of the plant. We’re looking at using hemp fibers, and we’re also looking at some more innovative approaches, such as hemp powder, for example. We’re looking at how we can use those materials to get a mix design that would be printable and at the same time environmentally friendly.”

Concerning modifying the hempcrete to be 3D printable – “We have a plan on how to do that. We have thought about different ideas, and we have some specific ideas on how to do it. What we’ve been doing so far, even prior to the formal initiation of this project, is that we have already started talking to producers and seeing what materials we have available, and discussing what we expect we would need. We have also had some preliminary work in those directions. We believe that our approach will address the challenge of having a 3D printable hempcrete mix design.”

As part of the research project, the team will explore the availability and accessibility of the quantities of hemp needed for this construction technique to be viable and sustainable. For now, “what I can tell is that in the United States, we know that there is a lot of interest in growing hemp and supporting this idea. Studies have already shown there is a lot of benefit to growing hemp for construction applications, so we expect that there will be no problem. The project will investigate that, though, and come up with more specific answers to those questions because, at this point, is an expectation that we have. It looks like there are lots of producers ready to jump on this idea, but we will have a more definitive answer once we do a more specific analysis,” said Petros Sideris.

When probed as to what Petros Sideris thought of the potential future for hempcrete, he had this to say:

“That’s very difficult to predict. I guess at this point we can only speculate in terms of the market. But if we try to just think in a reasonable manner, what we know is that the present construction practices are unsustainable – for example, building this massive number of homes using conventional concrete, and for this reason, it’s reasonable to expect that we cannot keep them for a long time. So, at the end of the day, to address these huge demands, you need to find a sustainable way to do it. In that sense, our project is in the right direction, and you can tell that a structure that addresses both sustainability and resilience is kind of the answer, or a potential answer, to the challenge that we’ve been facing, I would say as a nation [USA], but also worldwide.”

The formal research is expected to start this September, after the team has finalized the details with the Department of Energy, with the earliest possible results being published two years from now.