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Comment by woleium | Hacker News Reader

"The 5bn tonnes of cement produced each year thus account for some 8% of the world’s anthropogenic CO2, and generate abnormally high emissions per dollar of revenue earned compared even with other polluting industries (see chart). Yet if less than 0.1% by weight of graphene is added to the mixture, concrete ends up 30% stronger. And stronger concrete means less of it is needed, with a consequent reduction in CO2. "

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Hoping for the best, but hopefully this doesn't turn out to be such a hassle like asbestos :)

The question is does it shed nanographite or other nano-carbon particles and if so, at what level. Of course, open fires and photocopiers produce these particles as well so there is some level of background exposure that appears to be somewhat "safe". I expect the "no such thing as safe" crowd will be out if they sniff the opportunity for a witch hunt or 10 [1]

[1] https://particleandfibretoxicology.biomedcentral.com/article...

Comparing my concrete wall to a photocopier seems a little bit strange.

Why?

Because if I do not use my photocopier it does not emit anything, it just emit things during usage. In contrast I do not "use" my wall. It maybe emits things when it is newly made, but otherwise it does not emit things.

The same arguments was true for asbestos as well. Asbestos building materials are totally harmless if left undisturbed. But eventually that wall will have to be be repainted/sanded/drilled into/knocked down.

I did some IT work at a business that also was a training company for a long time and during renovations I had a desk between a server closet (like small room packed with servers hosting web sites) with no door on it and a massive "bizhub" style copier that was running constantly making training binders for the training business (yes, this was a while ago). My hearing was just shot at the end of each day and I was inhaling so much gunk from the printer that it was like living in a major city with a smog problem (as in stuff was coating the inside of my nose, my skin, etc). It took me a while to realize what was going on and I moved a few doors down to some older office space we had in the back of another business in the same strip of office spaces (this place had an ant infestation and no AC but at least I could breath again). It was a real eye opener in terms of noise/crud.

Are nanocarbon particles harmful? After all it's just carbon. Oragnisms should have a ton of mechanisms for dealing with it safely.

Even non-reactive particles like asbestos can cause a persistent inflammatory response eventually leading to cancer, chronic fatigue, malaise, etc. The ones that get the most attention these days are PM-2.5: tiny particles or droplets in the air that are two and one half microns or less in width, penetrate alveoli, and go straight into your blood stream.

More info: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4740125/

In about a decade or two brake dust pollution will be more recognized as a severe public health problem. It's not on the hype cycle yet. https://pubmed.ncbi.nlm.nih.gov/32593898/

Not just brake dust (which is probably solvable), but also rubber from tires.

But pure carbon is somewhat reactive, so maybe it could be cleaned by the body. Is it not?

Not sure, but there is definite collateral damage because it is biologically active.

From Fig 2. of https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7789336/

Mechanism of DNA methylation and histone modification alterations induced by nanomaterials and nanoparticles:

Exposure to NMs and NPs alters the functioning of chromatin-modifying proteins, e.g., DNA methylation and demethylation machinery, and histone-modifying enzymes, causing changes in the pattern of DNA methylation and histone modifications.

One of the most common effects of NMs and NPs is the induction of cellular stress, e.g., oxidative and endoplasmic reticulum stress, and metabolic disturbances, e.g., one-carbon metabolism and the citric acid cycle.

These events are causing DNA damage and repair response and metabolic alterations affecting the functioning of chromatin-modifying enzymes.

Any or all of these events may result in hypomethylation of DNA and altered histone modification patterns.

Additionally, exposure to NMs and NPs causes activation of the inflammatory response that, in turn, may cause DNA hypermethylation and histone modification changes

Benzene and similar flat aromatic carbon-based compounds are mutagenetic (cancer- and birth defect- causing) because they can slip between base pairs in DNA and disrupt replication.

I wonder whether graphene, itself a flat carbon compound, has the same affinity for DNA?

Molecular bond in benzene is little special. Maybe that's the source of mutagenic properties?

You'd think, but in fact biochemistry is quite bad at disposing of pure carbon compounds. You can test this: stick a pencil lead into some compost for a week and pull it out.

I still have a piece of pencil lead stuck in my finger from 24 years ago, though it has gotten smaller. And I know someone with a piece more than twice that old.

Doesn't it contain a lot of clay?

Carbon nanotubes are known to cause lung tumors.

Pure carbon really isn't something that a lot of organisms ever encounter.

Study on rats confirming this https://particleandfibretoxicology.biomedcentral.com/article...

I worry about structural safety ratios and the inevitable knock off products that end up failing after completion

You mean like what commonly happens in developed countries with standardised construction materials? /s

Or that it will cause another issue like aluminosis in the future. https://www.kaitekarquitectura.com/en/aluminosis/

Also caused by an additive (alumina) that made concrete stronger, but turned out later that it started to rot like crazy when it gets wet

It's would be golden if we could remove a great deal of the CO2 produced regardless of whether graphene was present in the mix. Or, hear me out, devise a concrete that reacted with atmospheric co2 to produce something more benign. That way it changes from an emitter to being a passive remover.

Poured concrete actually is a passive remover! The issue is the process of baking carbonate rocks at high temperatures to form the cement. This not only takes a lot of energy, but it inherently drives off CO2 from the rock. Over the decades as concrete slowly gets stronger and stronger it absorbs back a small but substantial fraction of the CO2 it emitted.

The way to make this better is to be able to have mixes with lower fractions of cement for a similar level of strength - hence using graphene in this case.

A passive remover but still a net emitter?

Yes, the concrete manufacturing process emits more CO2 than aging concrete absorbs.

Maybe the solution is dense, high rise concrete buildings surrounded by woodland. The size of the woodland being determined by the net emissions from the concrete.

The emissions occur during production. Concrete itself doesn't emit CO2, it's the cement being made from limestone that generates emissions.

I might even prefer that to living in suburbia if you also added room for commercial zoning.

I think the way we designed cities around cars could really stand a serious second look. Cars are really a necessary evil for me. I just bought one after 6 years of not having a car. I wish I didn't need it.

I hear that. We can put bike lanes and a tram track beside the building, shops and amenities at the bottom, and room for food trucks to come and go. It'll be perfect.

More seriously, sorry to hear about the car. It sucks to be that way. I've always been lucky enough to arrange my life around access to public transport (I don't drive) but I've been tempted many, many times.

Couldn't this be addressed best by driving the heat on green energy and directly siphoning off the produced CO2 into either underground capture or even green fuels?

I'm still a bit at loss why Climeworks or Prometheus Fuels would pump ginormous amounts of normal air through their respective setups to extract the 0,0004% of CO2 instead of feeding from pure CO2 by industrial processes like this one.

It seems like an easy win on the low hanging fruit to me, and I think there's work on making that practical from Noya Labs: https://techcrunch.com/2021/02/24/noya-labs-turns-cooling-to...

good point, but CO2 is ~415ppm = 0.4 per thousand = 0.04%

It could in theory, but as you say, nobody has created a practical way doing either of those things yet.

CO2 was actually too expensive for enhanced oil recovery for which it is often used since in many cases capturing it in an effective way from industry is just not possible or nowhere near economically viable even at high prices. Hence trump signed a subsidy for co2 sequestration to fight the climate change he didn't believe in.

Since pumping CO2 into the ground is technically just that (even if they don't really care much whether it actually stays there and oil comes out in the process).

Generally the solution to these problems whether it's co2 capture or power to gas at scale is not some future way to defy physics or edge our way up in efficiency towards a distant future where it might be viable but to just emit less. I suspect we'll look at this in the future the same way many look at the plastics industry's takes and propaganda about recycling.

I found out the hard way that the older concrete gets, the stronger it gets.

Was trying to make a 30cm x 60cm hole in a DIY concrete wall that the last owner of my house had placed over the mains pipe that was leaking from two joints underneath it (I suspect he also DIYed the piping, given its rather unorthodox setup). I had to make room for a plumber to access it.

It was poured in the early 70s, looked pretty, well, homemade, so I figured, easy! Borrowed a concrete breaker, got to it.

3 weeks, very painful wrists from the vibration, and a hired concrete saw, later, I finished my hole.

But holy crap, I had vastly underestimated concrete.

It takes about 40 years for concrete to reach about max strength. I've also experienced the fun of it having lived in a concrete building from the 70s :)

If the CO2 from cement production is mostly sequestered, it ends up being a net negative CO2 emitter. But that's not cheap.

This is a dream scenario, but something a bit more achievable...I would like to see more buildings designed with a longer design life, so we don't have to pour concrete on the same block multiple times a century. I wonder if current emissions calcs for "Green" buildings include demolition and reconstruction when they are past their use-by date.

> Or, hear me out, devise a concrete that reacted with atmospheric co2 to produce something more benign. That way it changes from an emitter to being a passive remover

Good propertyy. It would be even better if the material acted as a good insulator. And be re- or upcyclabe when we need to tear down the building. And while we're at it: it would be nice if the product would just grow...

That sounds like a tree to me...

So true...

Geopolymer concrete pretty much fits the bill for this. From my layman’s understanding the main reason we don’t use geopolymers instead of Portland cement is because we already have so much infrastructure for Portland cement

That's similar to how we already had so much steel infrastructure. The existing infrastructure didn't hold back the people who owned none of it.

https://www.nytimes.com/1981/09/23/business/the-rise-of-mini...

Like wood ;)

We should use more wood.

Rot is the main issue, I think.

Not if the wood is glulam:

https://en.wikipedia.org/wiki/Glued_laminated_timber

Consider this picture:

https://en.wikipedia.org/wiki/Glued_laminated_timber#/media/...

Your picture link should be https://en.wikipedia.org/wiki/File:Mj%C3%B8st%C3%A5rnet.jpg eh?

- - - -

The "Glulam versus steel" section is really interesting!

> A 2002 case study comparing energy use, greenhouse gas emissions, and costs for roof beams found it takes two to three times more energy and six to twelve times more fossil fuels to manufacture steel beams than it does to manufacture glulam beams. It compared two options for a roof structure of a new airport in Oslo, Norway: steel beams, and glulam spruce wood beams. The life cycle greenhouse gas emission is lower for the glulam beams. If they are burned at the end of their service life, more energy can be recovered than was used to manufacture them. If they are landfilled, the glulam beams are a worse alternative than steel because of the methane emission.[9] A more recent study by Chalmers University of Technology was not so optimistic. Nevertheless, it showed that while the absolute greenhouse emissions are strongly dependent on the method used to calculate them, the environmental profile of glulam is typically as good as or better than steel in an example structural application.[10] The cost of the glulam beams is slightly lower than the steel beams.

I'm also curious about the flammability. I did some Googling and wasn't able to find a concise answer. It seems like the beams themselves can be fireproofed with a non-wood cladding, or another study said they can be over-specced to give a 1 hour fire resistance rating. Another study said that steel connectors are typically used, and cladding for the wood-steel connection is an unresolved issue.

It seems like people are using them, so I presume it's safe. I don't think I would want to live in them until we've seen a bunch of them catch on fire. I'd probably be fine with it up to 3 stores, but anything higher would make me concerned.

30% stronger doesn't mean 30% less usage though so it would be interesting to see how much less concrete can actually be used in typical applications.

30% stronger might mean considerably more savings than 30% by weight, especially if the graphene concrete has better properties under tension (where concrete is abysmal). Stronger materials can have a larger volume to surface area ratio safely, picture an X shaped pillar rather than a full cylinder.

It depends a lot on situation. 30% stronger could mean even better than 30% less usage, when most of the weight of a structure is other concrete.

Economists have never heard of Yevon's paradox. Surprising.

Increased efficiency will lead to more use, not less.

I read this as less concrete used for any one application. It's also not clear to me that this would reduce net costs, as producing bulk graphene is likely not as cheap as any other conceivable additive. From an environmental perspective, if required volume is reduced but cost is the same, then worldwide consumption could be reduced.

It's cheaper than many other additives.

Graphene flakes are all that is needed for concrete reinforcement, and it's trivial to produce, even at scale. Carbon chunks are thrown into industrial blenders with water and detergent, resulting in graphene flakes sheared and then separated in suspension. The flakes are separated, washed, and dried.

Large graphene sheets are hard. Tiny flakes are trivial, gradeschool kitchen science.

For it to come into effect, the cost of the concrete should be a major part of its usage. This may or may not be true in this case, since there's land costs and a lot of regulations

It's "Jevons", and it is pronounced with a "j" sound.

https://en.wikipedia.org/wiki/Jevons_paradox

Interestingly this is also trending right now: https://news.ycombinator.com/item?id=31440518

Stronger concrete sounds much more interesting than just that less concrete means less CO2. Should open up some design possibilities for architects.

I'm guessing it's stronger in tension, which is not super useful for concrete which is only used in compression.

I'm not an expert but is that true? Road bridges are commonly concrete. In this application they use tensioned steel inside the concrete to help with the tension and other forces.

Yeah exactly. The steel resists the tensile forces and the concrete resists the compressive forces.

Concrete is very weak in tension. That's why it's basically never used without steel reinforcement. I think increasing the tensile strength is mainly useful to prevent cracking which looks bad and can allow water to get to the steel.

Or we build skyscrapers 30% higher.

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