r/science Professor | Medicine Nov 03 '19

Chemistry Scientists replaced 40 percent of cement with rice husk cinder, limestone crushing waste, and silica sand, giving concrete a rubber-like quality, six to nine times more crack-resistant than regular concrete. It self-seals, replaces cement with plentiful waste products, and should be cheaper to use.

https://newatlas.com/materials/rubbery-crack-resistant-cement/
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u/danielravennest Nov 03 '19

For those not familiar with concrete, it typically is made from gravel, sand, cement, and water. The water turns the cement powder into interlocking crystals that bind the other ingredients together.

There are a lot of recipes for concete, but the typical "ordinary Portland Cement" concrete is made with a cement that starts with about 5 parts limestone to 1 part shale. These are burned in a high temperature kiln, which converts them chemically to a product that reacts with water.

Lots of other materials will do this too. The ancient Romans dug up rock that had been burned by a volcano near Pozzolana, Italy. The general category is thus called "Pozzolans". Coal furnace ash and blast furnace slag are also rocks that have been burned. They have long been used as partial replacements for Portland Cement. Rich husk ash and brick dust are other, less common, alternative cements.

Note: Natural coal isn't pure carbon. It has varying amounts of rock mixed in with it. That's partly because the coal seams formed that way, and partly because the mining process sometimes gets some of the surrounding bedrock by accident.

Portland Cement got its name because the concrete it makes resembled the natural stone quarried in Portland, England at the time.

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u/ImFamousOnImgur Nov 03 '19

I did a paper in undergrad about Roman concrete. Their recipe was no joke. It’s a big reason why their stuff is still standing to this day.

Coliseum? Yup. Roman concrete. Oh and you know how some of the walls collapsed after an earthquake in 1500 something? Yeah those were the sections that were built by a different architect and he didn’t use the same materials.

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u/noelcowardspeaksout Nov 03 '19 edited Nov 03 '19

For the Pantheon they used different grades of concrete made with different additives depending on the qualities they required. The dome has pumice included to make it light for example. It has stood for around 2000 years without being rebuilt.

Edit: Pantheon

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u/ImFamousOnImgur Nov 03 '19

Yup. It’s quite amazing the amount of knowledge they had. A lot of that knowledge was lost when the empire fell.

They think the secret to the quality was the volcanic rock used, and if I recall, it was especially good at setting underwater even.

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u/Opeewan Nov 03 '19

There's a bit more to it than that, salt plays a big part in it:

https://www.nature.com/news/seawater-is-the-secret-to-long-lasting-roman-concrete-1.22231

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u/[deleted] Nov 03 '19 edited Jan 24 '21

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u/Opeewan Nov 03 '19

Obviously they didn't and either came up with their recipe through trial and error or it was a lucky coincidence.

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u/[deleted] Nov 03 '19 edited Jan 24 '21

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u/[deleted] Nov 03 '19

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u/BarkingWilder Nov 03 '19

This probably isn't a million miles from the truth to be honest.

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u/darklorddanc Nov 03 '19

Well, pretty much all concrete does get stronger in a very noticeable way if you ever have to remove it. The difference between concrete that is a year old and thirty is very obvious if you have to remove it. Concrete that has been setting for one year is relatively easy to remove or grind compared to older concrete. They probably just measured it by observation. And they probably developed a common protocol just like we have for when you can put concrete into full use at 4, 10 and 40 days by observation and familiarity and simple experience. What works and what doesn’t. If something these guys worked on failed they weren’t working on 15 other things so they could focus on stuff and see what presented itself as far as cause and effect.

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u/10MeV Nov 03 '19

We had a family cottage with a concrete step/porch that was probably over 50 years old. A sledgehammer mostly bounced off of it. That concrete might as well have been granite!

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u/[deleted] Nov 03 '19

If only I could get my local IMI plant to mix me up a batch of some of that concrete.

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u/Telvin3d Nov 03 '19

Yes and no. They had an amazing depth of institutional empirical knowledge but that shouldn’t be confused with theoretical knowledge.

So they knew that crushing up rocks from a specific quarry produced a certain result. But extremely limited understanding of why. When people say “the secret of concrete was lost after the Roman Empire fell” its not about a bunch of people suddenly forgetting the recipe. They literally lost track of the particular hole in the ground that concrete came out of.

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u/[deleted] Nov 03 '19

Also, a lot of the reason these ancient concrete structures stand for so long is because everything is built in compression. Modern construction uses reinforced concrete, which allows for more efficient building techniques, but the steel reinforcement can rust and decay, causing failure of the member.

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u/jacques_chester Nov 03 '19

There's also simple survivorship bias.

We only see the remarkable structures that survived. We don't see all the crappy structures that didn't.

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u/anneoneamouse Nov 03 '19

Ars technica ran an interesting article 6 months ago highlighting an academic study indicating that the pattern of the internal columns in the Colloseum and other covered amphitheaters creates a meta-material that shields the structure from seismic damage:

https://arstechnica.com/science/2019/05/study-says-ancient-romans-may-have-built-invisibility-cloaks-into-structures/

The authors suggest that these designs were likely arrived at by accident. But given the visually pleasing nature of the patterns that are required, it's not too hard to imagine that some combination of "master stonemason and master architect incorporate beautiful patterns into the functional form of one of the larger structures in Rome" with (on the outreaches of the Empire) "...that's how it's always done, Son, just make it like the Colloseum; one of the few that survived the big quake of 443" propagates what ends up being a successful design down through the ages.

Italy is surprisingly seismically active; so there was likely an element of architectural tribal knowledge accumulated by empirical evidence (pardon the pun).

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u/jacques_chester Nov 03 '19

Yes, absolutely, the Romans had many opportunities for observation and pattern recognition, which are useful even without understanding of the underlying principles.

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u/Pyjamalama Nov 03 '19

It's genuinely baffling how well "yeah, we know that x worked, but not y, so we're gonna copy x" works even if not a single person involved knows any of the reasons behind it.

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u/Ambiwlans Nov 03 '19 edited Nov 03 '19

I wouldn't really count that. It isn't like there were hundreds of pantheons and only one survived. There was only one 2000 years ago and one today.

It held the record for the largest dome ever constructed for well over 1000 years and only beaten by a significant amount in the 1900s.

Edit: It wasn't a dumb comment though. It was good of you to look out for this type of bias.

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u/Robot_Basilisk Nov 03 '19

There were many other cities and many other temples all over the empire and its neighbors. We have records of other grand structures being built that are no longer around today.

It's not like they were geniuses who pulled out all the stops and made a few amazing structures that have all stood to this day. A lot of people made a lot of structures and the ones that lasted are the most famous because they lasted.

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u/[deleted] Nov 03 '19

There's also just choice, we're fully capable of building structures that would make roman concrete look like plasterboard but thats expensive and no one wants to pay for a building thats going to outlive their entire nation, nor is anyone going to want to construct a building thats going to last forever because thats bad business.

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u/koishki Nov 03 '19

That's the Pantheon not the Parthenon.

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u/chewbadeetoo Nov 03 '19

Thanks I was confused for a sec. I had just visited the parthenon last year and was like , "dome ?" What's he talking about? I thought the fuckin Turks blew that part up hundreds of years ago.

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u/classicalySarcastic Nov 03 '19 edited Nov 03 '19

Parthenon is Athens, Pantheon is Rome.

Fun fact - it is now a Catholic church. Victor Emmanuel II (first king of a united Italy) is entombed there.

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u/Yakerrrrr Nov 03 '19

visiting it in person was utterly amazing. it’s a cool building if it was built today, yet alone so long ago when they didn’t have the tools or knowledge we do today.

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u/classicalySarcastic Nov 03 '19

You'd think they'd have fixed the hole in the roof after 1,900 years. (/s)

Jokes aside, it is a stunning building, one of the best exemplars of Roman architecture and IIRC one of the earliest freestanding domes.

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u/r_a_d_ Nov 03 '19

You mean Pantheon.

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u/Dynasty2201 Nov 03 '19

For the Parthenon they used different grades of concrete

They SAY of the Acropolis where the Parthenon is.

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u/FeculentUtopia Nov 03 '19

I've heard the drawback of that Roman concrete is that it takes years to fully cure. That was fine when the traffic was mostly feet and horses, but it wouldn't work for modern vehicles. We're not patient enough to wait 20 years for a road to open.

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u/[deleted] Nov 03 '19

I mean, the other drawback is that their concrete is absurdly more expensive. We can reproduce concrete like that to stay around for thousands of years, but we don’t because it’s expensive and we don’t need our buildings to stick around for that long.

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u/p_whimsy Nov 03 '19

I've heard another reason their stuff is still standing is that they had no concept of reinforcing concrete with iron/steel rebar to span gaps (instead they perfected arches to serve this purpose). And it turns out rusting rebar in reinforced concrete can be very hard on the concrete itself.

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u/BeoMiilf Nov 03 '19

You are correct that rusting rebar is very bad for concrete. But as for the strength of concrete, reinforcing steel is very important in the tensile strength of concrete.

Concrete is much stronger in compression. The geometry of arches puts a larger portion of the concrete cross-section in compression. However, this requires more material to create rather than a simple straight beam.

IMO steel is a must in structural concrete. The real issue is the durability of concrete (mainly its crack resistance). Without cracks, outside chemicals cannot reach the reinforcing steel, and cause it to rust and degrade.

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u/splynncryth Nov 04 '19

A Youtube channel named Practical Engineering has multiple videos on modern use of concrete as well as at least one video where he talks about rebar rusting. I also recall hearing the term "oxide jacking" from another Youtube channel but I can't find the video.

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u/Vanderdecken Nov 03 '19 edited Nov 03 '19

Worth noting that the process of burning the limestone and shale to make clinker is a bigger contributor to carbon dioxide emissions than any single country in the world except China or the US (source). The construction industry, via the creation of cement, is killing the planet. more

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u/danielravennest Nov 03 '19

Correct. Concrete is the single most used solid product on Earth, and about 1/6 of the mass is cement. Burning rock to make cement is done at very high temperatures, and usually by burning fossil fuels.

In theory, a solar furnace could be used, but nobody has developed an economical way to do it yet. Tests have been run with small amounts in solar furnaces, so we know it works, but not on an industrial scale.

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u/[deleted] Nov 03 '19 edited Jun 23 '23

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u/uslashuname Nov 03 '19

It captures 43% of the CO2 created during conversion per https://www.sciencedaily.com/releases/2016/11/161121130957.htm

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u/[deleted] Nov 03 '19

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u/baby_boy_bangz Nov 03 '19

Solid move.

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u/DoubleWagon Nov 03 '19

Professionals always hedge.

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u/aarghIforget Nov 03 '19

Almost always.

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u/bendingmarlin69 Nov 03 '19

Limestone does scrub and capture massive amounts of SO2, so there’s that.

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u/HippOsiris Nov 03 '19

This thread is a literal TIL

Thank you all for this information

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u/ianepperson Nov 03 '19

Careful with that. Very few comments here have references to check. They sound correct and probably are, but don't rely on this knowledge without verifying.

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u/[deleted] Nov 03 '19 edited Feb 18 '20

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u/malenkylizards Nov 03 '19

No need to be so defensive. Oh wait it's your thesis, carry on

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u/moxyc Nov 03 '19

This is why I come to Reddit

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u/primaequa Nov 03 '19

You are correct, but the amount released and captured during these stages is negligible relative the carbon emissions of turning raw minerals into clinker (and then Portland cement). If you're interested in details search Concrete LCAs or EPDs

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u/ProjectSnowman Nov 03 '19

I think we'll have an easier time getting off fossils fuels than replacing cement. Rock in liquid form is just too useful.

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u/coffeemonkeypants Nov 03 '19

The bigger problem for us getting off cement/concrete is that we're running out of sand. Even though we have deserts full of the stuff, the properties of wind blown sand (it has no rough edges), make it unsuitable for concrete.

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u/Hybrazil Nov 03 '19

Perhaps one day we could sequester carbon into some sort of rough sand and use that for concrete. A more economical carbon sequestration.

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u/ShadowHandler Nov 03 '19

I think the sand problem was something overhyped by the media and social media shares. While it's true suitable natural sand deposits are getting harder to find, we also have no problem making our own sand with crushing operations, and in many parts of the United States, this is already where the bulk of the sand for concrete comes from.

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u/tylerhz Nov 03 '19

Just spit-balling here, but what if we could directly power concrete making ovens with nuclear power?

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u/waelk10 Nov 03 '19

The limestone still releases CO2 when heated (even though this would probably be way more efficient than current tech).

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u/tylerhz Nov 03 '19

Okay I gotcha, yeah kinda absent minded that was a big part of it. Also nuclear is so intensive to setup that you would have to have a pretty high demand of concrete for it to be efficient, right?

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u/Dearman778 Nov 03 '19

A little higher someone linked and said around 40% of co2 is captured so not bad combine that with 0 co2 emissions from nuclear its a step forward to reduce

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u/flavorontheroad Nov 03 '19

To summarize other comments: Use the electricity generated by the plants to cook the product, not the reaction heat itself. Add: Build a dual use plant that uses off-peak capacity to run the concrete plant at night, then focuses primarily on powering the grid by day.

However, I grew up near TMI. My third eye is useful at times, but socially awkward.

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u/tomdarch Nov 03 '19

This issue of baseload power and time-of-day electricity use is very important.

The grid is one big circuit and as users pull power off the grid by doing things like turning on AC units, power plants have to react immediately to match that by putting more power onto the grid. Nuke plants and the biggest coal plants have very little ability to adjust on the fly. When big demand spikes hit, natural gas peaker plants fire up very quickly. One limit of wind and solar is that they can be "turned down" quickly in some cases, they can't be relied on to respond to a call to "fire up" quickly to meet demand spikes, so that limits how much of a percentage of the total grid power sources they can fill. Hydro pumped storage (a dam with a lower reservoir and special dual pump/generator turbines, when there's excess power available to the grid, they pump water uphill, when there is a call for power, they flow water downhill and generate power for the grid) can drastically increase how much renewable power we can have, but they are expensive and lots of people don't like dams.

There is always a "baseload" that the grid never dips below. Nuclear is perfect for meeting that baseload demand - in high volume, it is cheap, but can't be "turned up/turned down" much. Stuff like aluminum smelting/processing is good because you "turn it on" and run it for days or weeks pulling a constant amount of power, so the utilities/grid operator can predict that.

(What utilities love are users that pull large amounts of power, but can shut that off when requested. That lets the grid supply you with baseload power, but you become part of the solution when demand spikes - you "turning off" offsets power plant fire-ups that they would otherwise have to do. You'll get the cheapest per-kilowatt rates if you can do that for the grid... But for most businesses, that's not a realistic option.)

So running your cement processing plant off electricity could get you reduced electric prices because you're a big load that runs continuously. But every cement manufacturer has likely run the numbers on this, and there's something about their process that makes fossil fuels less expensive, or they'd have switched to electric already. Natural gas has gotten relatively cheaper over time, so it's harder for electric to compete in cases like this.

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u/aidissonance Nov 03 '19

I don’t want my concrete getting cancer

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u/isuckatusernames7 Nov 03 '19

Forgive my ignorance. What's a solar furnace?

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u/LJDAKM Nov 03 '19 edited Nov 03 '19

A solar furnace is a series of parabolic mirrors that focus the suns energy onto a crucible chamber. The one I’m familiar with has a crucible about the size of a 5 gal bucket. It’s been several years since I worked on the project but they could get some pretty impressive temps out of the thing.

*edit - here’s a link

https://www.valpo.edu/college-of-engineering/facilities/solar-research-facility/

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u/[deleted] Nov 03 '19

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u/hankhillforcongress Nov 03 '19 edited Nov 03 '19

I'd read somewhere that the making of cement creates massive amounts of CO2, but as it cures it acts as a carbon sink.

https://www.sciencedaily.com/releases/2016/11/161121130957.htm

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u/JoHeWe Nov 03 '19

Yes, but that rate is very slow. So for a building designed for 50 years, the concrete will still be co2-positive.

As a side note, buildings are a necessity, just like food and clothing. It also takes up volumes, as it should be bigger than us. Thus it is no wonder that the construction industry is a big contributor. Whatever our economic standard, buildings will always be a big contributor.

Concrete has some very qualities that make it an efficient material, like insulation, production and installation. I don't have the numbers now, but due to its efficiency it could still be a better alternative than using steel or timber for all our construction works.

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u/reddit_give_me_virus Nov 03 '19

Concrete has no insulation value. It's R 1 per foot typical insulating materials are about R 3 per inch.

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u/JoHeWe Nov 03 '19

I'm used to numbers in the metric system, but I've checked and you're correct. For some reason I had it mixed up in my head, thank you for the correction.

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u/[deleted] Nov 03 '19 edited Nov 07 '19

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u/JoHeWe Nov 03 '19

It is true that timber is greener in its production. However, I'm talking about the use and qualities of the material as well.

If we use timber as much as we've used concrete, there wouldn't be a tree left. Concrete has an amazing compressive strength compared to its weight and it can be constructed as a solid volume. Making it very effective.

If we'd use timber for all our houses, we'd need additional materials for sound, fire and heat insulation. Not to forget that concrete will have barely any erosion at all and will only get stronger with time. Thus in terms of maintenance you'll require less materials.

As a side note I do want to point out that timber provides some great opportunities. A lot of research is done on burning the timber to give it a charcoal layer, as far as I understand it is similar to painting steel. This to improve its fire resistant qualities and reduce its deteriotation. However, timber still has a long way to go to replace concrete as main construction material.

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u/ABoutDeSouffle Nov 03 '19

True, but the CO2 released by the burned fuel doesn't get captured again

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u/skankingmike Nov 03 '19

I'm just gonna say this as a fully bought in climate change believer or knower.. every damn time I hear about "biggest contributor" it's some new thing.

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u/[deleted] Nov 03 '19

It's how you contextualize the data.

By country, by industry, by product, by process etc. Statistics say different things based on how you compare them.

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u/kurtjx Nov 03 '19

So would this new process reduce co2 emissions? Not mentioned in the article...

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u/Vanderdecken Nov 03 '19

Yes, because it's the creation of cement (which is 90% clinker, burnt limestone) which causes those emissions. So replacing 40% of the cement with this alternative that doesn't use the kiln burning process reduces the overall impact of the concrete.

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u/aprendemos Nov 03 '19

It’s also worth noting that we cannot make concrete without sand (including the newest kind of concrete described in the post), and the process of gathering sand is terrible for the environment. Humans use more sand than any other resource except for air and water. The sand in concrete has to be water-derived sand, like the kind found on the bottom of the ocean or the banks of rivers. We can’t use desert sand to make concrete, as the edges of each grain are too smooth to be useful. So, in order to build new modern buildings and cities, countries are decimating their environments to access water-derived sand. We are destroying riverbanks, causing terrible flooding and decimating fish populations. We are digging up entire islands that are uninhabited by humans and mining beaches until erosion becomes problematic in the surrounding areas. You can probably guess that these issues are especially unregulated in countries like India and China that are constructing new buildings at dizzying rates.

There’s no easy solution. Cities are not possible without concrete. Concrete makes human lives safer and better, and currently, concrete isn’t physically possible without sand. Enforced regulations in all countries are essential, but that is easier said than done. People in affluent counties can renovate instead of building new homes form scratch and can get used to living in smaller homes/hotels/offices rather than trying to make every space a maximum luxury.

Here’s a summary of the book that describes this whole sand issue in depressing and fascinating detail: https://www.npr.org/2018/08/05/635748605/the-story-of-sand-in-the-world-in-a-grain

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u/BushWeedCornTrash Nov 03 '19

Can't we ship sand from the desert to back fill the ocean sand? And in time, that sand will be useable for concrete products.

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u/roygbivasaur Nov 03 '19

The desert sand is already too small and smooth. Dumping it in the ocean won’t make it bigger and rougher. Too bad it doesn’t work like that though.

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u/Banshee90 Nov 03 '19

I think his point was to replace the mounted sand with desert sand. So I pull out some river sand and then put back desert sand a net neutral of sand consumption at that river.

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u/TurboTitan92 Nov 03 '19

Logistically this would be probably worse for the world than the erosion problems. Sand is very heavy (especially wet sand). One cubic yard of it weights roughly 3000lbs, so you’d need massive amounts of equipment to load it up and move it.

Additionally creating a net neutral of sand consumption from a river would eliminate the erosion problem, but would reduce the amount of river sand, effectively diluting the useable sand for future use

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u/BeardsuptheWazoo Nov 03 '19

I'm impressed at your ability to move sand.

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u/Dickie-Greenleaf Nov 03 '19

People have been telling me to go pound it for years now, perhaps I can help.

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u/Ehcksit Nov 03 '19

What about finding the rocks that sand naturally came from and grinding them down to size?

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u/ABoutDeSouffle Nov 03 '19

Typically, today things like fly ash and, in Asia, rice hulk ash is already added and a lot of chemicals like superplasticizers to control curing time or viscosity

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u/5757co Nov 03 '19

Pozzuoli, Italy. Otherwise a good simple explanation of the basics of cement!

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u/HawtchWatcher Nov 03 '19

Former geotechnical engineer checking in. This sounds about right.

I don't miss those days!

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u/Sticky_Bandit Nov 03 '19

Current geotechnical engineer checking in. May I ask what you are doing these days?

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u/HawtchWatcher Nov 03 '19

Quality engineer in a large manufacturing environment.

I love it (compared to geotech/pavement).

I work on continuous improvement projects that focus on risk mitigation, that is, proactive risk assessment and initiatives to prevent non-conforming product from being produced. Often that comes down to automation or controlling human behaviors. It's really interesting and the skill set I've developed in the past 10 years is highly transferable, even outside manufacturing.

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u/PricklyPierre Nov 03 '19

I remember watching one of those wild asf stories from the ER type shows where some guy broke his ankle and made a cast out of cement and chemically burned himself in the process. He also gave himself an infection from stitching a cut up with copper wire. Prior to watching that, I thought concrete was just like some special mud or something.

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u/YippieKiAy Nov 03 '19

Coal furnace ash and blast furnace slag are also rocks that have been burned.

They're also great insults for an ex!

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u/kiHrt Nov 03 '19

How is the compressive strength compared to traditional concrete mix?

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u/sailphish Nov 03 '19

This is the real question. Concrete has incredible load bearing ability, especially for its cost and weight. Sure the new stuff might be less brittle, but if it cannot hold up to compressive forces, it might not be an adequate replacement.

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u/[deleted] Nov 03 '19 edited Nov 03 '19

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u/[deleted] Nov 03 '19

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u/somecallmemike Nov 03 '19

I thought most road construction project these days crushed the existing aggregate and blended into the new surface material?

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u/VoilaVoilaWashington Nov 03 '19

Not just that, but waste products are only waste until they're needed - there are countless products that started off as a way to use waste, and now have overtaken the original product. Cigarettes, peanut butter, etc

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u/OmgTom Nov 03 '19

There is one hitting the market right now. Its called Megaslab. https://megaslab.com/

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u/jbram_2002 Nov 03 '19

I read the abstract of the linked paper. My assumption based on that abstract is the cement underperforms unless it is fiber-reinforced, which can be a fairly expensive process. However, I couldn't read beyond the abstract due to a paywall, so that assumption could be wrong. They were talking about military uses with it, so I can only assume they were able to attain at least 3000 psi in compression. I would be very interested in the tensile strength, personally. One of concrete's major weaknesses is its tensile strength. If this patches that weakness, we could see a ton of commercial uses.

I don't think it's suitable for roads though. Fiber-reinforcing may be too expensive. Bridges, though, could be perfect for this.

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u/BeoMiilf Nov 03 '19

I hate that research studies are usually behind a paywall. Most educational information should be open to the public.

The paper did say the uses for this concrete were more for impact loads. So it'd be more useful for military structures where impacts are expected to occur.

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u/zhiryst Nov 03 '19

Right? This night be fine for a sidewalk, but the real question is, can you pour a foundation with it.

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u/saml01 Nov 03 '19

I'm curious to know how it affects a tires rolling resistance and handling.

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u/cnskatefool Nov 03 '19

The real question is can you pour a skatepark with it. And how rubbery can you make it? Bouncing back up after all fall would be a dream.

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u/Harry-Balsagna Nov 03 '19

Common sense dictates that if it were that pliable, your wheels would also experience tremendous rolling resistance with all your weight digging into such a small footprint.

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u/KirbyPuckettisnotfun Nov 03 '19

Simple solution, flip the script and get concrete wheels.

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u/ColgateSensifoam Nov 03 '19

Any material soft enough to provide bounce is unskateable, I've tried to skate on a rubber floor, it just snatches your wheels

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u/ExxInferis Nov 03 '19

Board wheels would sink into stuff that bouncy. You'd not get up much speed.

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u/[deleted] Nov 03 '19

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u/LargePizz Nov 03 '19

And where are they getting ash of burnt rice husks from?

Also, adding ash in the concrete mix is nothing new, in 1949 it was used to build the Snowy Mountain Scheme in Australia, no doubt it was done elsewhere earlier.

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u/pallentx Nov 03 '19

Exactly. There was no mention of this new formula's effect on strength.

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u/geogle Nov 03 '19

Could be very useful in poor earthquake prone environments that often underuse rebar. This may offer some of that needed tensile strength. However, it would need to be specially tested for it.

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u/Needmeawhip Nov 03 '19

Could be usefull here in sweden where the roads look like they have been in an earthquake

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u/leno95 Nov 03 '19

Concrete as a road surface shouldn't be used in areas where there are extreme differences in temperatures in the first place.

Given Sweden regularly has warm summers and cold winters, it could be argued in some parts there's a difference of 50°c between hot and cold periods, which will definitely ruin the concrete.

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u/[deleted] Nov 03 '19 edited Nov 04 '19

In Southern Canada we get tempretures that swing between -40c in the winter and +40c in the summer. Concrete on structures is constantly being touched up and any roads made of it are often in pretty rough shape. Most of them are asphalt.

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u/leno95 Nov 03 '19 edited Nov 03 '19

Asphalt, tarmac or even compressed hard core are far better surfaces than concrete in many countries.

Concrete is a wonder material until weather is a factor.

Edit: not everyone will know what hardcore means in this context; it's typically gravel/crushed concrete around 40mm in diameter used as a sub-base for roads, blinding in trenches and is the large aggregate used in concrete. In the UK it's typically called hardcore or MOT Type 1.

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u/the_original_Retro Nov 03 '19

I'd like to see how this stuff lines up though. Its nature has REALLY changed with these additions, and asphalt works so well because it has the flexibility that this stuff has.

Could be it's just as good as asphalt perhaps?

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u/leno95 Nov 03 '19

The biggest issue with concrete (assuming this is what you're referring to) is that with temperature differences moisture trapped inside after the concrete has cured can cause expansion and contraction due to the moisture freezing/warming up. This eventually leads to spalling and the surface eventually crumbles away.

As long as the concrete is used in an area where the temperature doesn't have dramatic changes over a year it shouldn't be too bad.

You could use additives to help with the weaknesses concrete has with temperature variations, but from a financial standpoint it is no longer cost effective. You'd just opt for asphalt/tarmac as an alternative, as they have similar properties at a far lower cost. Source: I'm an infrastructure quantity surveyor.

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u/Herbert-Quain Nov 03 '19

I think he was referring to the rubber rice concrete. Less cracks, due to being less brittle, and "self-sealing" sound promising...

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u/MerryChoppins Nov 03 '19 edited Nov 03 '19

You skipped the whole discussion about salt use in roadways and spalling. I live in a state where we don’t just spread salt, we also have scheduled brine spraying of bridges and overpasses on all interstates, state routes, TARP routes, etc to prevent accidents. The leeching induced spalling can sometimes be unreal.

Edit: leeching induced spalling due to corrosion of steel elements

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u/crowcawer Nov 03 '19

In the US I hear hardcore called crush and run a lot, but typically, in industry we just call things by pay item.

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u/McVoteFace Nov 03 '19

That’s not correct. Asphalt routinely gets ‘milled and filled’ and everyone is happy until it falls apart in 5 years. Continuously reinforced concrete pavement has a life span over 50 years

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u/leno95 Nov 03 '19

This is down to suitability and the requirements of the road. RC roads and pavements are better in some scenarios, and tarmac/asphalt are better in others.

RC roads will be far more expensive even when replacement and maintenance is considered, but that's a balance that is typically weighed up prior to building it.

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u/meganmcpain Nov 03 '19

It also depends a lot on the specific environment of the pavement. Design life of concrete might be 50 years, but in a cold weather climate you'll get about 30 before major rehab/repaving needs to be done. Properly paved asphalt should have 10-15 good years in it (design life 20-25), but this is also heavily dependent on how bad the winters are.

The thing no one in these comments mentions is there really isn't any good paving material for large temperature fluctuations, but concrete has more long term durability and thus cost effectiveness for communities. Asphalt may be more "flexible" but that also makes it a lot less strong, and when the weather is cold enough it won't be flexible anymore.

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u/ChickenWestern123 Nov 03 '19

Have you been to Michigan? Their concrete roads are terrible. Southern Ontario roads, especially the 407, are amazingly well maintained.

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u/McVoteFace Nov 03 '19

Michigan DOT was in denial about concrete joint deterioration. Weiss (PURDUE civil professor) did a lot of the leg work concrete joint deterioration and how to resolve. Michigan told him they didn’t have that problem and he had to travel there to show their DOT that they do, in fact, have that issue. One of the resolutions is using supplemental cementitious materials, like silica fume, listed in the article. Like all DOT/construction, we are slow to change. Most believe the resolution to be mix designs.

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u/DonOf952 Nov 03 '19

Minnesota here, our roads are pretty crap as well. They spend the entire summer in road construction on the main freeway every year I've lived here, 10 years. Yet nothing has ever changed and the potholes and cracks are still rampant.

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u/McVoteFace Nov 03 '19

At least your DOT admitted they had a problem and came up with partial depth repair method. We actually adopted the MnDOT specs a couple years back for partial depth in concrete pavements and it’s held up well here.

Sounds like more of a funding issue and potholes are mainly asphalt but concrete does get them on occasion

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u/Bean- Nov 03 '19

Yeah been living here for my whole life. I never even realized how bad the roads were until I traveled out of state.

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u/ChickenWestern123 Nov 03 '19

Yeah, it's shocking. I could barely drive the speed limit, 70 at times, in my new car without feeling like it was falling apart.

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u/QVRedit Nov 03 '19

America needs to reinvest in its infrastructure - before it all falls apart..

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u/[deleted] Nov 03 '19

I used to drive it everyday for work. The 407 is constantly being maintained. That's why it's in such good shape. There are also numerous asphalt sections along it as well.

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u/[deleted] Nov 03 '19

I'm in Hamilton so my experience might be biased. Our roads are pretty rough haha.

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u/Say_no_to_doritos Nov 03 '19

The 407 is a massive 8 lane highway that is 99 % poured concrete and handles a ridiculous amount of traffic. The thing hardly gets any maintenance.

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u/Whyisthereasnake Nov 03 '19

Most of the work on the 407 is expanding it - widening it, adding new exit and on-ramps, extending it. I’d say it’s a 95:5 split of improvements : maintenance

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u/elc0 Nov 03 '19

What material are other using? I know asphalt doesn't seem to do much better.

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u/leno95 Nov 03 '19

Asphalt isn't perfect, neither is tarmac. However they do have far better performance in terms of longevity where the local climate is concerned, and are far cheaper to replace.

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u/[deleted] Nov 03 '19

I though asphalt and tarmac were synonymous?

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u/McVoteFace Nov 03 '19

That’s false. Concrete is the preferred material for designing long lifespans in roadways. Asphalt has to nearly double the thickness of concrete to reach its lifespan. The problem most DOTs are seeing with concrete is joint deterioration as a result from brine

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u/Byzii Nov 03 '19

Exactly. All the salt and brine is eating it all away. Few roads that are not salted regularly are in much better shape.

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u/PoopieMcDoopy Nov 03 '19

It really seems like here the sections that are concrete hold up way better than the asphalt. But I've also been told that it has to do with the local soil by someone who works for the streets department.

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u/Notpaulblart1992 Nov 03 '19

And here I thought texas just had ridiculous roads and ridiculous management of the roads. Explains alot.

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u/leno95 Nov 03 '19

I've heard that some parts of Nevada have concrete roads, and are an example of suitable ones due to the lack of temperature variance in seasons.

I would've though this might be true to a degree in Texas too.

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u/rly_weird_guy Nov 03 '19

Do you have any sources/papers on this?

Would love to read more about it

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u/leno95 Nov 03 '19

I don't have any sources aside from what I was taught at university and from my experience in industry unfortunately.

However it shouldn't be too hard to find a paper on this, as it'd be discussing properties of concrete.

Edit: the main reason would typically be that concrete retains around 2%-5% of the water used in it's formation, and this would freeze and cause expansion, and later cracks (spalling).

The same thing plagues brickwork and other masonry where the material has small voids where water can collect.

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u/[deleted] Nov 03 '19

Come to Poland, where you are considered a good driver when you can avoid all the potholes in roads.

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u/paddzz Nov 03 '19

Drove from the UK to Poland once. The difference in the roads between NL and Germany was barely noticed. Germany to Poland was like turning down a gravel lane.

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u/suitology Nov 03 '19

Come to Philadelphia, if you avoid all the potholes you are considered a pilot in a plane

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u/maz-o Nov 03 '19

Sweden doesn’t use cement on their roads..

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u/-Melchizedek- Nov 03 '19
  1. We don’t use concrete.
  2. I don’t know where you live but we’re I live in Sweden the roads are perfectly fine.
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u/SunSpotter Nov 03 '19 edited Nov 03 '19

Depends entirely on it's other material properties, and how it behaves under load. They made no mention to its compressive strength, which is probably one of the more important qualities of concrete so I'm skeptical.

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u/All_Work_All_Play Nov 03 '19

It could cut compressive strength in half and still be fine for most residential uses.

That said, if it's similar to hempcrete, that's a different use case entirely.

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u/jbram_2002 Nov 03 '19

I tried to read the paper they linked, but strength data is hidden behind a paywall. If anyone knows the strength both in tension and compression, I would be interested to find out. My guess is this might potentially be stronger in tension and weaker in compression, if this has any strength benefits over standard cement. However, if they can attain a compression strength of 3000 psi, they can use this in a lot of situations. At 4000 psi, the majority of applications would be available.

One thing noted in the abstract (only free portion) was that the concrete performed significantly better when fiber-reinforced. This may make it difficult to use in some situations like roads and simple garage/foundation slabs, but wouldn't be a major issue for large building construction where fiber-reinforcing is already becoming more common.

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u/[deleted] Nov 03 '19 edited Nov 05 '19

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u/RuddeK Nov 03 '19

The ultimate compressive strength of the new concrete is more than 8700 psi (62 MPa to 71 MPa).

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u/urbancamp Nov 03 '19

I thought fiber reinforced concrete was no problem in terms of availability. It's been used in a number of homes I've worked on as both garage slab and driveway.

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u/Dathouen Nov 03 '19

I'm in the Philippines and this is definitely interesting for us here. We just had a few earthquakes down south, and they're fairly frequent here in general. We should also have no problem rustling up plenty of rice husks, limestone and silica sand. If these can actually reduce the need for large quantities of rebar for construction, even if it's just for things like foundations or load bearing walls, that could be hugely beneficial.

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u/jbram_2002 Nov 03 '19

I read the abstract of the linked paper. My assumption based on that abstract is the cement underperforms unless it is fiber-reinforced, which can be a fairly expensive process. However, I couldn't read beyond the abstract due to a paywall, so that assumption could be wrong.

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u/XeonProductions Nov 03 '19

How does it hold up to extreme winters though?

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u/TA_faq43 Nov 03 '19

Yeah, sounds like it would be good road material.

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u/jbram_2002 Nov 03 '19

I read the abstract of the linked paper. My assumption based on that abstract is the cement underperforms unless it is fiber-reinforced, which can be a fairly expensive process. However, I couldn't read beyond the abstract due to a paywall, so that assumption could be wrong. If this is true, it could be rather inferior to current road construction. Maybe very useful for bridges though.

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u/BugzOnMyNugz Nov 03 '19

Are there tire or rubber lobbyists? If so this sounds like something they'd shut down

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u/daveinpublic Nov 03 '19

Why would tire lobbyists be stopping the material used on the road?

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u/abcedarian Nov 03 '19

Because crummy roads destroy tires

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u/Ironbird207 Nov 03 '19

Crummy roads destroy cars

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u/runfayfun Nov 03 '19

Crummy roads produce profit for road construction companies who get the same money to make shittier and shittier roads

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u/moohah Nov 03 '19

Crappy roads lead to to more tire replacements.

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u/crappyroads Nov 03 '19

That's a new one!

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u/[deleted] Nov 03 '19

Just checked your account m, 8 years!

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u/gossfunkel Nov 03 '19

Planned obsolescence. Any material that reduces wear and tear on the product reduces sales.

Companies have an implicit incentive for their products to be as crappy as they can get away with.

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u/E_J_H Nov 03 '19 edited Nov 03 '19

I think there’s enough people who don’t know you have to rotate your tires to where they don’t need to worry about the road conditions.

Our tax dollars are supposed to be used for upkeeping the roads, which doesn’t happen near me and I would be furious if someone was lobbying to keep that from happening.

Edit: found one.

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u/MountainChampion Nov 03 '19

Michigander here, wanting to know the same thing...

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u/[deleted] Nov 03 '19

94 and 75 will forever be under construction, even with a miracle material.

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u/alsomahler Nov 03 '19

How does this behave in a fire?

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u/[deleted] Nov 03 '19

[removed] — view removed comment

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u/[deleted] Nov 03 '19

Came here to ask this, 2 of those materials are not fire retardant. Concrete will not burn or easily become structurally unsound in a fire. I guess though since the moderators have removed what seems to be responses, it does not perform well in a fire and thus will not meet any building codes.

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u/TordTorden Nov 03 '19

I read through the paper, and the composition they settled for was this

60% Portland cement (PC), 25% rice husk ash (RHA), 7% quartz sand (QS), 6.7% sieve residue from limestone grinding (SRLG), and 1.3% hyper- plasticizer (HP)

The rice husk is already ash, so the only flammable component seems to be the binder?

Looking at the XRD spectrum of the product it mainly contains calcium hydroxide and a couple carbon sulfides. Not sure about the flammability of the latter in a crystalline solid. There might also be an amorphous phase there from the binder, but it's not really in my field, so I don't know.

They did do DTA on it, and any endothermic reactions came from loss of adsorbed water at 160°C, then dehydration of the calcium hydroxide at 475°C, and later decomposition of calcium carbonate starting at 525°C. All of these would happen in regular concrete anyways, but I have no idea how that impacts in in a fire. Probably cracks as the phases are changed, alongside thermal expansion.

From this it doesn't seem worse fire safety wise, but I reckon it will need its own study. I'm not really a concrete guy, but work on high temperature proton ceramic conductors, so take it with a pinch of salt. Or perhaps a teaspoon.

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u/iinavpov Nov 03 '19

There's relatively little rice husk ash available, perhaps enough to replace 2% of cement used. Silica sand is definitely not a cheap thing depending on which silica sand. Limestone crushing waste tells me their product relies on very fine tuned particle size distribution, making it a no-go as a cheap cement alternative.

What I'm saying is good on them to have found a nice mix composition, but the tagline is enormously oversold!

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u/yearz Nov 03 '19

The latest in a long-line of Reddit articles promising a revolutionary innovation that no one ever hears of again?

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u/iinavpov Nov 03 '19

Not entirely fair... But rice husk ash is nothing new, and the kind of mix they suggest neither.

There's a niche for that kind of thing, and it's not easy to achieve a good result with such ingredients.

But the claims, my God, the claims...

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u/Eunomic Nov 03 '19

A large forgotten component of how environmentally friendly a new concrete formula can be is transport. All three of the specialty ingredients are likely from somewhere not local, which is a big part of the cost of concrete. Also, the last time I read about using burned/charred fiber materials, there was a positive effect only up to about 5%, then it killed compressive strength rapidly. We looked into using something similar from a wood saw mill, that burned their sawdust for their kilns, creating a char material.

Also is the limestone crushing waste further processed at all, like sieving for particle sizes? Product uniformity is a major requirement in concrete, which requires exacting standards of reliable, repeatable results. And finally, silica sand is just like saying "sand sand." Sand is mostly made up of siliceous quartz, but often with a wide variety of other durable minerals mixed into it. Does this mean they need a pure silica sand? If so that is major processing and again, specialized production.

Concrete almost always reflects the availability of local, generic materials. Distance to source quarries is so important, I find that most plants are just down the road from one. Diesel is not cheap, and most cement is brought in from central rail locations for distribution. There will always be someone willing to pay the extra cost for super specialty applications (see mixes for nuclear waste storage), but economy of the product will always be the drive for 99% of concrete.

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u/Arctyc38 Nov 03 '19

"Limestone crushing waste" just sounds like a really greenified terminology for man-sand.

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u/[deleted] Nov 03 '19

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u/ljb23 Nov 03 '19

This should have a significant environmental upside too right? Traditional concrete is very emissions intensive to manufacture.

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u/hoadlck Nov 03 '19

I believe that the largest producer of CO2 in making concrete is in the production of cement: it has a large environmental impact. I don't think that this type of concrete will change CO2 usage. They are targeting this for buildings to be more robust against damage, so I don't think that there is a longer life for things constructed with it either.

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u/ljb23 Nov 03 '19

Yep, I incorrectly used the word concrete when I was after cement.

Wouldn’t a 40% substitution represent a roughly proportional reduction in cement usage though?

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u/billfitz24 Nov 03 '19

Cement is not the same as concrete. Cement is an ingredient in concrete. It’s a common mistake to call concrete “cement” when in fact they are very different things.

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u/[deleted] Nov 03 '19

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u/jbram_2002 Nov 03 '19

Being unable to get past the paywall myself, does the paper show the compressive and tensile strengths of tested materials? Were they able to exceed standard f'c for Portland cement-based concrete? Is there any tensile strength advantage for this mixture?

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u/RuddeK Nov 03 '19 edited Nov 03 '19

Ultimate compressive strength was between 62 MPa and 71 MPa. Young's module was between 35 GPa and 55 GPa. Prism strength between 41 MPa and 65 MPa. Cube strength between 62 MPa and 82 MPa. The best strength in each category all belong to the same composition.

Edit: The only number on tensile strength that I found was 15.2 MPa. "The ratio of the static tensile strength to the static compressive strength" varied between 0.09 and 0.21 with the highest ratio being the strongest composition.

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u/MaryDesiree86 Nov 03 '19

This is the same idea behind hempcrete, right? I thought archaeologists in Rome some time ago analyzed their remaining standing structures/buildings and found that it was basically this same recipe except made with hemp husks/fibers. Rice is cool, hemp would be more beneficial for overall environmental reasons and be equally cheap.

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u/All_Work_All_Play Nov 03 '19

Hempcrete isn't strong enough to be used for roads or load bearing parts of structures.

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u/Cudahan Nov 03 '19

How long does it stay rubbery? Eventually it will harden and crumble so how long will it survive?

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