Why Some Roadways Are Made of Styrofoam

🌉Have you ever hit a bump going over a bridge?
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"A catastrophic loss of function" is just the most hilarious and accurate engineer-speak for "the building collapses on you."

Thanks for making this. Living in Seattle as a member of a family of civil engineers, I was pointing out the use of styrofoam in the construction around the viaduct southern entrance. My mechanical engineer colleagues refused to accept that the styrofoam was used for structure, insisting that it must be temporary packaging waste! I'll happily share this video with them.

In Scandinavia it is common to use styrofoam as foundation material for buildings. The thermal disconnect is highly desirable when its -20 C outside, and it provides a very good stability when ground changes shape due to freezing water. Maybe an interesting subject for a video?

"Soil is heavy. They teach us that in college!" is the funniest thing I've heard today.
Also, I learned that those "abandoned" highway construction sites that I have been complaining about for literally decades may not in fact be due to scheduling problems or lack of funding. They were probably just waiting out the settlement period. It's stuff like this that is why I love this channel.

Your content just keeps getting better and better! Big fan of EPS and using it more and more in my industry too.

As a Lab Technician for ENGEO I would like to thank you for all your videos. They serve as training aides for our interns, and help us explain what we do and why we do certain testing in a simple and entertaining way. We can show them your videos and then what we use in our lab setting. Keep up the great work.

I worked for an EPS manufacturer many years ago and one of their contracted projects was scrap EPS blocks to go into the middle wall and other sections of a dual tunnel roadway. The grade was usually a SL or L grade (Super Light or Light) EPS block, up to 5 metres long, by 600mm by 1.2m. For its size, they're very light. Saved the joint venture construction partners millions in fill and related costs, plus gave the EPS company plenty of work besides making sheets insulation and lobster boxes.

Two really great lines in this: “catastrophic loss of function”, and “soil is heavy, they teach us that in college”

Thanks for making this video. I live in the Netherlands, where large parts of the western part of the country are basically glorified swamp. In my new neighbourhood, the decline is 2.5 to 4 centimeters a years, and have been declining at this rate for about 30 years now. The locals often refer to the peat ground as "thick water". All houses are build on poles, that reach a layer of sand 7-10 meter deep, and are stable. However, gardens and roads are not. Over time, in particular the roads have subsided (not really settled, as it is still declining) and the common solution was just to add another layer of asphalt on top of the parts that settled too much. Of course, that added a lot to the weight, so it settled even further. They found that by now some parts of the asphalt were 1.5 meter thick. After some heavy rain they decided to tackle this and for the whole village, street-by-street, and replace the heavy roads with low-weight material that basically floats on top of the thick water (also known as "ground"). It's a 10-year project, and interesting to see. Other solutions were tried as well, like excavating the borders of a neighbourhoud up till the sand-layer 7 meter deep, and replacing it with clay. This basically turned the watery ground into a bath tub: all the peat (thick water) in the middle would be contained by sand underneath and impermeable clay on the sides. In theory, this should stop the decline of the ground. In practice, it failed. It just keeps declining about 3 centimeters every year.

Can confirm: I worked as an Operating Engineer and placed many thousands of yards of cellular concrete all over the country and our primary work was on bridge embankments and abutments, especially in the Bay Area of California. We also did many abandoned pipe fills using it for pressure grouting and some interesting annular fill projects too.

About 25 years ago, I was part of a geotech team tendering for a second bridge across the Swan River in Perth, Western Australia. The ground was very soft alluvium, and the embankment needed to be quite high. We proposed a stabilised soil fill over foam-core solution, but were unsuccessful - the Main Roads Department were very conservative (and still are), and went for a conventional (and much more expensive) pile-supported solution. Nice vid, thanks.

Grady, I just finished reading your book and it was such a pleasure! It was fun to learn so much about the "boring" world, and you've imparted your curiosity on me as well. The illustrations are awesome.

Here in Canada when a section of the trans canada highway was being upgraded from two lanes to four lanes there was a section of about 2 km crossing a swamp, the swamp had muskegs that were over 90 feet deep, and the engineers used drills and bored into the swamp using tubes to collect the water, and diverting it into pumping stations, then the whole thing was built up with geofoam. All of the drilling and piping techniques are covered on this channel.
Thanks for the great content:)

Chemical engineer here, but fascinated by the topics you cover here! Thank you for letting us into this mysterious world around us and making it simple to understand

Oh man I still remember when sand compaction video came out and introduced us to your channel., time really flies. Your content has been consistently amazing,, always looking forward to what you got for us. I'm not a civil engineer, but I just love learning from your channel.

You inspire me. You make me feel at home for wanting to be an engineer who wants to help people. Thank you so much, Grady. For lifting my spirits. For showing me there are other people who care about the weird nerdy stuff that I like and won't make fun of me for just trying to help.

That is what I live for--an easy-to-understand explanation of something I was only vaguely aware of. Grady, this is, hands down, one of my favorite youtube channels, and one that I share often with other people.

This is literally one of the best channels on UAclips. You’re such an amazing teacher, Grady. The way you clearly and concisely lay out the information in a very easy to understand manner is one of your biggest strengths, next to your knowledgeability. You make me look at the world differently and wonder what things are for, and why they’re designed that way. This leads me down many internet rabbit holes of information gathering, but they’re not as fun as your videos lol

I think a major takeaway that transcends industries and disciplines, is the fact that the least expensive suitable material does not always result in the net least expensive finished product.

I'm always impressed with the quality of content you and your team makes Grady! Keep up the great work

I'm so glad I found your channel, I never knew how much I loved civil engineering. It really is fascinating how the world we use works

03:35 As a NJB fan, I loved how you made sure to show 9 entirely different buildings/businesses being demolished or affected by the hypothetical bridge catering to car traffic.

Thank you for another wonderful video! Speaking of using styrofoam for thermal insulation, I work for a small mountain railway where we sometimes battle with frostheave (also a video idea? ;) ) We experimented with using styrofoam in the subgrade to prevent the ground from freezing. It worked well as insulation, but unfortunately the ballast stones have a knack of punch through the sheets under load!

I have been watching your channel since you were doing wood turning and Arduino projects. I got your book at Christmas and am enjoying it very much. Thanks for all the work you put into your videos. It is worthy of praise and recognition.

I saw the EPS used for an overpass in my area. The road needed to go over a train track, and was in a developed area so the embankment had to be as thin as the road. As well, the area was partial wetlands so settling was likely a substantial concern.
I had always thought it looked like styrofoam, interesting to find out that it was exactly what it looked like!

I love how you demonstrated EPS' weakness to fuel spills by essentially making Napalm.

This video made me think about arrestor beds installed at the end of some runways. I'd love to see a video on those and it was interesting to read how some of these same materials are used.

I love your videos so much, and they’re one of the reasons I fell in love with civil engineering and why I’m studying it in college. Thank you for your hard work and incredible videos!

I’m a 3rd year Civil undergrad and man. I love these videos so much! Winding down my day after dynamics and mechanics of materials to see the application and connections from the learning is awesome!
Much love from Florida 🤘🏼🤘🏼📐🔩

It's really inspiring to see your family (and cooking confidence lol) grow as your channel does! Keep up the great work, Grady!

One of our local bridges has an approach underpinned with Styrofoam, it wasn't protected properly and rats got in there and made enough tunnels that the surface of the approach started to subside.

I'm much more intrigued by the floating concrete than the styrofoam, to be honest. It's in that category of "ordinary thing given counterintuitive properties," like making clear wood or boiling water at below-freezing temperatures in a vacuum. Weird materials are fun in general. Carbon nanotubes! Aerogel! The mysterious sticky stuff my nieces leave on surfaces they should have no reason to touch!

I'm a Geotech Engineer who mostly works on PennDOT and PA Turnpike projects, and I approve of the definition of "a heavy pile of dirt" haha. We geotechs are often pretty chill because we spend lots of time playing in the dirt and working with that understanding that so much of what we do is working with nonhomogeneous materials, interpolating between borings limited by funding, and factoring for safety. I'm fairly young, so I haven't had the chance to work with lightweight fill material yet.

ive seen big cubes of styrofoam under a road during construction and thought it had to do with frost management, but now that ive seen your video i remember that it was on some part of an embankment for a highway overpass...
gotta learn something every day!

When you mentioned the buoyancy of EPS it reminded me of the Fraser valley floods in Canada 2 years ago where the ground water made the eps filling float and that broke the road on top of it.

I tend to consider a larger environmental impact of highly processed substances such as plastics compared to naturally occurring backfill soil. However EPS has inconceivably low density around 20-30 kg/m^3. In EPDs I reviewed, both Global Warming Potential and Energy Use during manufacturing are lower than even wood products for unit 1m^3 of element. Maybe one also needs to check its interaction with its environment, impact to local ecology etc. Great video btw, Grady!

As a person who is not an engineer, civil or otherwise, thank you for this video. I had a feeling that, this is why many projects around town take forever. I know this is just a primer, but still valuable information none the less.

My grandfather started an EPS company back in the 70s (Plymouth Foam). I was so surprised to hear they had a contract with a major local construction project to fill in under the new roadways and embankments. This was so cool to see on here. Thanks as always for putting out the entertaining and educational content you do.

Your channel is just the most amazing thing! Stuff that seems incomprehensible is suddenly made clear, even to me! I cannot tell you how much I appreciate this. Too many engineers are so entranced by the science that they forget to explain the form, function and desired outcome. Thank you for being different! 🇨🇦💕

Man I just love how passionate and informed you are on engineering processes and challenges.

We had a section of a 4 lane divided highway near us that just kept sliding down the mountain. After decades of lane closures and repairs, they finally just removed the soil/clay in that section and replaced it with Styrofoam blocks. One would never know that you are driving over thousands of giant Styrofoam blocks. I marvel at how stable the area is now, while wondering how often I am driving over Styrofoam on other roads.

I wish you had discussed the environmental downsides of Styrofoam. It's probably the worst of all plastics. I am curious if roadway engineers have mitigated any of those issues or if they just ignore them for the short term benefit of "completing the project quickly".

Haha, awesome!
I have seen those gigantic styrofoam blocks used as floating devices and have even lifted one (it feels unreal how lightweight it is, given how huge volume it has) and also seen them being used during construction of pipelines for district heating (in that case for heat insulation). But I could never think they would be strong enough to use for whole road embankments, haha. That's cool. The foamy structure and light weight also means very little material can be used to fill up a huge volume - which cuts down cost and environmental impact during manufacturing.

I remember watching the Apple Park construction timelapses years ago and seeing them build the hills out of what looked like blocks of foam - it’s good to finally understand why that was!

Hi Grady, thanks for nice video. I can confirm based on my own experience that this is working. I did time ago (as young engineer) the design of retaining wall (embedded structure, wall supported by laterally loaded piles). Because of mess in the project it turned out that wall has to be locally extended from 2m to 3.3m height (6.6ft - 10.8ft) during construction. To challenge that I thought that lateral force depend on backfill weight, so it needs to be replaced with lighter material. That was idea to use EPS blocks as most available light material. Then I did small research and discovered that similar solution was used in my country. That ensure me it is good idea and I implemented this into design. Despite structure is not impressive I am still very proud of that design.
Greetings from Poland.

A cool application of lightweight concrete is the concrete canoe competition a lot of civil engineering students compete in. As a mechanical engineer, it's really neat to see floating concrete!

I know those huge Styrofoam blocks real well. In Nov 2012, I worked with Superior Construction delivering precast concrete wall panels to a new bridge over railroad tracks on Industrial Highway (now renamed Airport Road) in Gary Indiana. The bridge deck was steel/concrete, the approaches were done with six levels of these huge foam blocks topped with sand/asphalt. The wall panels we delivered contains the sidewalls to keep the foam blocks from shifting and to keep them from rising and/or floating away during periods of flooding. Important since this location is only 3/4 mile away from Lake Michigan. This project coincided with the expansion of the Gary Chicago Intl Airport. The local rail line that used to cross the north end of the airport property where the expansion occurred was moved further north to join the railroad east/west mainline, which also utilizes the new bridge, East Chicago Ave between Cline Ave and Industrial Hwy was removed. It was an impressive project which is highlighted on the airports north end on Google Earth. I took a few photos on the project and now 11-years later, it still stands. That was the first time in my 39 years in construction transportation being involved with a project that used Styrofoam as a base material. Besides the airport, the area is heavy industrial with heavy truck use and it has held up very well.

"Soil is heavy; they teach us that in college!" had me genuinely laughing out loud, thank you, Grady!

"Soil is heavy! They teach us that in college." -- This is the type of engineering humor I expect here 😆

Thank you for this amazing explanation. I saw blocks being used for some roadwork (embankments) and I assumed they wouldn't be strong enough to handle the compression of vehicles going over, but you've proven me wrong. Also, I use that highway overpass many times a week and it has yet to fail. Also, I agree with your wife, waiting that long to get to dinner is a *huge* "I'M HANGRY!" problem.

Years ago I was watching a new construction project in progress near my home and was amazed to see them using the foam blocks. I wondered to myself how long it would take for ground digging animals to discover these and make a nice warm home out of them.

"Soil is heavy, they teach us that in college!" Haha, that one caught me off guard and gave me quite a chuckle. Well done Grady, well done!

As a retired mechanical engineer I absolutely LOVE following your channel. VERY interesting info presented in a fun way. Keep up the good work Grady

A few years ago my exit on the Denver Boulder turnpike had a partial collapse due to soil settling/movement (soil expansion and contraction is common here because of high clay content). They ended up using styrofoam blocks as the fill material which probably wasn't an option back when the highway was first built.

I drove across northern Scotland last summer on the North Coast 500 route and stopped at a place called Moine house up on remote boggy moorland. There was a sign there which said that the original road crossing the moor which had only recently been replaced was built on top of bales of heather to stop it sinking into the peat. This road was hundreds of years old.

I love your videos, always so informative. You make learning about roads fun!

I used to make geofoam, actually did for that exact seattle project. We used something we dubbed 2 pound it is about 10 to 15 times as dense as what you get as packing peanuts, but each 4 ft by 4 ft by 8 ft block was only about 300 lbs. Light enough to be moved very easily. Some of these blocks were even cut to order at the plant before being sent to the project. They would then only need to make minor tweaks to the foam to ready it for the roadway.

Thanks for the informative video. Driving past the viaduct project I always wanted to know more. Please consider doing more videos on Seattle’s unique projects like the viaduct tunnel, West Seattle Bridge, or our many drawbridges!

I used to work near and frequently see work on the project depicted at 12:09 (this is at the southern end of the SR99 tunnel in Seattle that replaced the Alaskan Way Viaduct), and was always curious abut all the styrofoam they were using there. To put it mildly, the soil a lot of Seattle is built on, especially near the waterfront, is seismically questionable (one of the main reasons to get rid of the Viaduct in the first place) so it makes sense to make things as lightweight as possible in that area.

I'm a DOT certified inspector and I've worked on a road project where they built up a section of the roadway 3 lanes wide about 40' long and 15' high using styrofoam blocks because they didn't want the weight of the fill on top of some old but still live pipes under the roadway.

love this channel. VERY educative and makes us think more about the vital infrastructure important to us all

Before I began following this channel I thought of infrastructure as marginally boring and something that, well, could be given for granted a little bit. Got slightly pissed off at some irregular sections of highway, found bridges nice or ugly and that was about it.
Now, after being a subscriber and having watched a lot of these videos (many a lot of times) I find it extremely interesting, a real engineering product and something to get excited about --this video in particular reminded me of a huge shopping center that has been built close to my home, and how they were making the structure lighter by adding EPS to the reinforced concrete where it was possible.
Also, next Friday I will probably obsessively looking for bumps before driving over bridges, although I must say that I hardly remember any. But I will probably pass a construction site where they are widening a highway that needs to go over a bridge: maybe I will get a glimpse of how they are constructing the embankment and let you know if they are using something interesting to fill it.

A few years ago I found a huge block of concrete just, sitting on the beach near my house. It was baffling how or why that could've ended up there but a piece of it was broken away and it was actually a block of styrofoam coated in concrete. But I was still very confused. Tried to look it up and found some stuff about styrofoam being used like that in construction, but not really why.
This explains it.

It’s always a good day when there’s a new edition of Practical Engineering.
I wonder if lightweight materials might help absorb road noise and vibrations.

I enjoyed this a lot and I hope we use styrofoam more in the future because that's super cool!

Grady's new book "Engineering in Plain Site" is a must have! Got it in the mail a few weeks ago and enjoying one section a day and learning tons. Fantastic!

Here in Pennsylvania most road construction drags on long enough that everything has fully settled by the time paving takes place lol. Love the videos! Thank you.

Yes! There's annoying bumps on each end of bridge going over the freeway. I believe problem could be fixed by filling the transition points with a smooth material, or by covering with rubber mats.

This has opened my eyes on why I see so many construction sites that looked abandoned. I just hope half of them are really waiting for the soil to settle!

I juat love how you put so much thought and effort into your content, and i know you get some kickback from the sponsors, but its of your own volition that you make it in the first place. You contribute to wider human knowlege and i cant thank you enough for that

I love all your content, very educational. These structural videos always gets me wondering how I can get some of these materials or use these methods at home. Either with my driveway or house foundation. Or hire a company that uses these methods.

there was a critical failure of the embankment under a highway near my home, and when they replaced it, they used geofoam instead of traditional backfill, it was surprising to see, but made perfect sense, cause they were building next to a reservoir, so the soil had compacted under the traffic load so much that the roadbed actually fell away in a small landslide across most of the southbound lanes, emphasizing the need for a lightweight backfill material.

Thank you, I have often wondered why. I see a lot of styrofoam used at the on and off ramps of bridges.
There is a particular place where I live where it's used in the road construction, going over a marshy area, two places in particular, and it's a noticeable drop after only a few years. They have replaced one of both sides of the short stretch a few times, since I have lived in the area, the most recent being last year after a once in 100 year flood eroded the sections of the highway significantly. I am curious as to why they would continue to replace these two sections the same way every few to several years, knowing that, in my opinion, it is not a permanent fix?

Interesting video! It seems to me as best used in special conditions over settlement prone areas. I can’t imagine the cost of making embankments out of manufactured material to be cheaper than re-paving due to settlement 🤷‍♂️. I do get excited to see new tech in the earthworks world though!

I had a summer work on a road construction a few years back. The site was on a former seabed and wasn’t hard as rock. We used expanded clay as filler on embankments. There was a huge pool of it after the bridge. We used also tons of expanded clay concrete under the roads.

I saw this process being put to use recently on the I75 rebuild through Metro Detroit, watching this jogged my memory of driving the the office and on the northbound lanes seeing giant blocks of foam being used to build an on ramp between 2 large concrete retaining walls going from the service drive at ground level to the subgrade roadway below.

You have a true gift for taking complex issues and making them easy to understand.

On our most recent Alaska trip we watched workers install EPS sheets as part of the Dalton Highway out to Prudhoe Bay. Waiting in yet another construction delay we enjoyed talking to a couple of workers who said the material not only helped by lowering the weight of the road surface, but also acted as insulation against blacktop and vehicle movement-created heat affecting the permafrost under the road.

Fascinating! I had no idea this was a thing! I have a question, though, Grady...
One of the problems with EPS is that it's notoriously unrecyclable and non-bio-degradable. Obviously that's part of _why_ it makes a good lightweight backfill material, but I can't help but notice that they're freshly cast blocks made specifically for this purpose.
Could shredded post-consumer/post-industrial styrofoam be used instead, like an aggregate? It'd be denser and a little heavier than the blocks, and weaker, but it would also be basically free (possibly even negative cost). Possibly a good compromise between the engineered blocks and the foamed/expanded aggregates? Or would it be too springy? I'm picturing something kind of like sandbags filled with shredded EPS, so there's some interlocking and added strength, a little like the reinforced aggregate from your early video.

I remember in elementary school in the '60s in the San Fernando Valley learning about all the ways the state was thinking of to fix the San Diego Freeway (I405). And there have been multiple times and ways the SoCal freeways have been "fixed"... 😃
Thanks for the very entertaining education. 👍

I travel across a bridge that had a rough and jarring bump. The DOT repaired the entrance by drilling holes and pumping some material under the existing slab on the embankment. It was interesting that it took maybe an hour to complete the entire process, and the bridge entrance feels almost level as a result.

I watched a road crew use the styrofoam bricks to build up an embankment for I-44 a while back. they were building an entire new interchange with 44 that used fancy J turns. it completely relieved all traffic that was waiting to get on or off 44. pretty sweet!

Hi Grady. We had pipes burst this winter due to freezing, and it got me thinking: How does the city get water to people in the winter without pipes bursting all the time? Perhaps you could do a video on that if you think it would make a suitable topic.

In the netherlands we always use a concrete slab that rests one side on the structure, the other side on the ground. This way, the "bump"' created by settlement, is also distributed more evenly. We still use lightweight materials a lot too though

In model trains and other scale miniature dioramas, styrofoam or other foams are often used to create and shape terrain - really funny to see it happen in full size to make roadways as well

I saw a road being built in the late 90’s with big blocks of styrofoam. Now that I think about it, it was right next to a bridge. Thanks for explaining why they used styrofoam.

I make Geofoam. It's always cool to see how it and it's alternatives are used to solve design challenges. Thanks for making my day.

This is crazy timing cuz I JUST learned about concrete lifting yesterday, saw some cool Timelapse’s from a company’s channel here on UAclips. They were using polyurethane foam type stuff to fill voids and lift entire stretches of sidewalk, porches, road, whatever. Super neat

A few tears back. A 2 lane highway was expanded about 20 miles south of me. One of the things done was to replace an old, narrow, steel bridge. As I watched the progress of the construction of the new bridge. I noticed they were using huge foam blocks at both ends of the approach the the bridge. It's been in use now for several years, and I've passed over it countless times. I have not noticed any detrimental effects because of it. Time will tell though. I understand that the weight of the roadway, and vehicles, which includes trucks is spread over a large area because of the large blocks. Still impressed that so far, the blocks themselves haven't compressed even more than they normally would. It's now a modern 4 line highway.

The thermal insulating properties of EPS foam have also been used in geothermal areas to reduce heat damage to the pavement. It was interesting watching construction of several hundred yards of roadway in Yellowstone National Park.

It not only the weight of the ramp that makes the surface go down, its also because its hard to compact materials in the ramp.
This means the traffic will compact as time go by.
I have seen it in my own work as one who administrate the maintenance of civil works (bridge, wharf, tunnels, stairs, support wall, ect)
(Sorry, I'm coming a bit short in English on some of the specific technical expressions)

You make engineering look so easy. Just the way it is.

What I somewhat missed in this video is how environmentally friendly are those artifficial backfill materials and foam concretes - how much energy does it use to produce, does any filling material leach out some chemicals?

Watched these blocks being placed on a project near work and had no idea what the purpose was. I had (incorrectly) guessed maybe it would aid in digging back down in a temporary setup. This now makes perfect sense! They were filling about 35 feet over a newly installed drainage system.

When a highway where I live was being extended, one of the huge challenges was a sub soil called leda clay. It's probably one of the most unstable soils around especially if it gets wet. There was no way to reroute the highway, so the engineering solution was to install a capping membrane, then use styrofoam blocks on top to build the bridge embankments. The styrofoam is ballasted with normal aggregate materials and paved. It hasn't shifted in the 10 to 15 years since it was built despite the heavy trucks that run on the highway.

We used foam sheets used for insulation to lay out our small swimming pool. It's notn the biggest load ever, but it's still 8 tons worth of water. The sheets can take the beating quite well. What they don't like is if the load is concentrated in one place (say a heel or a knee hitting the bottom of the pool). We have added "grass like" carpet in between to protect the foam further. It's been like this for a few years now, and it hold up quite well.

Now I know why it took over 3 years to complete the overpass in my local area: waiting for compaction. I had thought it should only take a year or less.
BTW, letting a small child learn meal prep while at the stove top seems a bit sketchy for later on when they decide to do something 'all by myself'. However, letting them learn at a countertop is fabulous! Props to the parents for taking the time to do this.

8 years ago we built a net zero energy home. In addition to our solar array, we are heavily insulated. We live in MN so insulation was very important to our construction. Our footings and concrete sub grade walls are wrapped in EPS foam to reduce thermal bridging. this means the weight of our entire house is resting on foam. After 8 years I can tell you that this system worked for us, we are living a warm life in our cold MN winters! Cheers!

When I saw the title of this video I instantly thought of the SR 99 tunnel project in Seattle. I may be wrong but I thought most of the geofoam used on that project was for temporary fills across the tunnel approach lanes.
That SR 99 project would make for some good videos from you, both in the complexity of the tunneling so close to other things, just a few feet in some cases, the repair of the TBM and the complex demolition project of the old viaduct.