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  • Writer's pictureNed Patton

Composites in Infrastructure 4 - What's New and What's Coming


I wanted to start this one with some info that I got in an article in ASME News. The pic to the left is a 3D printer at the Advanced Structures and Composites Center at the University of Maine in Orono. Working with Oak Ridge National Labs, they have developed a method of taking wood waste and turning it into a reinforcement for plastics. They use a plant based thermoplastic resin made from corn or other plant waste, bind it together with this wood flour and form it into pellets. These pellets are then put into their huge 3D printer and they have been able to3D print the framing for a house. Here’s a link to the article: https://www.asme.org/topics-resources/content/lab-to-build-wooden-houses-with-a-3d-printer.

The intent of this initiative, funded by DOE and managed through Oak Ridge, is to develop technologies for the “factory of the future”. The program goal is to use bio-based materials, 3D printers and AI to create large pieces of infrastructure, parts for the automotive sector, and other large scale parts that are basically wood flour reinforced bio-composites.

I put the pic of the 3D printer at the top because I found in an article about infrastructure and composites that really shows off what can be done, where a company has come up with a way to build a house (actually more like an ADU) that arrives on a truck and unfolds into a house. The pic to the left and the one below this paragraph are images of a house that costs about $33k and that three people can assemble in 6 hours. And it doesn’t even need a concrete foundation. Just tie down the four corners of the house and it will pass all of the current building codes.

These two pictures and some of the other pics in this post tell a story about what is coming in the way of new materials and product forms in the construction industry. Once the 3D printer demonstrated by U of Maine becomes widely available, and accepted by the Uniform Building Code in the US, houses like this ADU that came on a truck to the construction site will become the normal way that houses are built. Things like fir 2X4's and wood framing will become something that is only used on occasion for special structures where the aesthetics are more important than the actual structure. These are some of the first steps to sustainability in the infrastructure and construction industry. Great progress is being made.

Another example of fiberglass truss structures is the pic to the left of a truss structure that looks a lot like a steel truss frame, and is assembled in much the same manner. All of those yellow I-beams and the yellow square tubing going up the center of the frame in this pic are fiberglass structural framing materials. They are put together with adhesives and bolts, sort of like how steel is welded and bolted together, so the people who do this kind of construction already have the skills to put something like this together. And, since the fiberglass beams are about a third the weight of steel, while being as strong and nearly as stiff as their steel counterparts, very large truss structures can be assembled in less time, using smaller lifting equipment and less labor.

This truss structure could have been made using the framing members shown in the pic to the right (included in a previous post). These are from a company called Strongwell that has been in the composites business for some time. This product is trade named EXTREN® because they are pultruded shapes made using either glass/vinyl ester or glass/polyester composites with some UV inhibitors added. So, they are environmentally friendly as well as being very long lived materials.

The picture to the left is another example of composite materials making their way into the infrastructure business. This is a photo of the replacement of the sanitary sewer system in Los Angeles. The old cement sewer pipes are at their end of life and need to be either replaced or repaired in some fashion. Most of those sewer lines were installed in the 1950’s and they are wearing out. California has some of the strictest environmental regulations in the country, and there is also a strong push to make as many infrastructure projects as possible environmentally friendly or “green”. So the City of Los Angeles decided to re-line these old sanitary sewers with a composite material non-circular liner – because the original sanitary sewer lines were also non-circular. Using the composite liner sections that you see in the to the left, they were also able to rehab these lines very quickly. Since the sections are light weight and install easily, they were able to achieve pipe relining rates of nearly 2000 feet a day. Since they had 60+ miles of sewer line to replace, using these composite sewer line sections saved a lot of money.

Finally, the pic to the right is of a culvert cover that is made of a chopped carbon fiber thermoplastic. These are made by a company in the UK (Fibrelite) that is a subsidiary of a US company by the name of OPW. They make all sorts of covers for infrastructure, manhole covers, trench covers like what you see in this pic, and a whole host of other access covers for buried infrastructure that have traditionally been steel. They are about a quarter the weight of the steel covers, extremely wear resistant, corrosion proof, and have a much longer life span than traditional steel access covers. And, since they are so light weight, they are much easier for workers to remove to gain access to what they need to inspect or repair. This is an example of where the properties of composites – especially the weight and long life span – coupled with decreasing costs for the raw materials have gotten the attention of designers of infrastructure. And these access covers can easily be made to be a direct replacement for the worn out or damaged steel access covers they replace.

That’s about enough for this post. I’ll probably conclude my infrastructure posts with the next newsletter in this series. It’s not that I have run out of things to talk about in this space, it’s just that I think it’s time to move on to something new.

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