The cities are already perpetually under construction/maintenance and still, there's decade-old potholes in some places. Electrified cement: how much more maintenance effort will that take? Are the economic and environmental benefits worth it? It could be

Also, if it's a smart city and big tech is involved, think of the scale of the planned obsolescence issues

This has to be a racket to extract as much public money as possible. At least in the US and in most cities I have been, projects take years and they usually only send a few guys to work on it about once per week. A few years later they suddenly finish everything in a few months.

Are those workers at home or are they at other job sites with closer deadlines? In other words, is the squeaky wheel getting all the grease?

In software, projects take years and they usually send a few guys to work on it for eight hours every day. A few years later they suddenly decide to rewrite everything and never finish it.

Really it comes down to allocation of (affordle) resourcing and the bidding process construction companies have to do for the cities.

Typically the teams you see are being split between several projects and one construction project mnanager is managing several projects.

Then throw in city permitting and inspections which take an awful amount of time and expense.

Is there a reason it's slow? Yes, they're trying to keep budgets low. However there isn't a reason it needs to be slow.

When there's a political will and cultural to do it fast and safely, it gets done. That bridge collapse in Philly on i95 took like 10 days to repair. It also probably cost a lot to repair as well but there was a political will to do it because of how critical that infrastructure is.

Same goes for bridges and highways on California destroyed by earthquakes or landslides. Those get rebuilt quickly but the cost to do so is very high.

That’s generally optimizing for cost over speed, empty sites are cheap and going slow tends to save money. It also lets the company constantly move people through a backlog of projects at different locations rather than adding a few people then having breaks in work where you have to let people go.

There is also real physical limitations when moving dirt around. If you quickly make a big pile it settle quite a bit. So instead you add a few inches at a time and bring out heavy equipment then let it settle, do some tests, and repeat.

https://youtu.be/22W5tRWbUVI

> The cities are already perpetually under construction/maintenance and still, there's decade-old potholes in some places.

Talk about endless construction, see London. Improvements come gradually with new construction, then the old are propped up/covered up/stripped-and-refaced as long as they are useful and upgraded when convenient.

The UK is astronomical with how it does their permitting, planning, and PM.

Oxford's wolvercote roundabout took like 3 or 4 years to complete for what could have amounted to a year of work for any American crew.

Want to hear a joke? Skanska workers working.

I think it is reasonable to expect a city to be perpetually under construction and maintenance.

Your average architect is barely managing the coordination of their structural, electrical, mechanical, civil, and plumbing engineers. As green adaptive technology accelerates, it deeply concerns me that our notoriously slow moving construction and design industry will fail to incorporate these technologies and deliver the built environment we need to succeed against climate change.

This technology is great, but the real breakthrough will be getting someone like Lennar homebuilders to incorporate this into their constructions by default.

> This technology is great.

Not yet it's not. There's a world of difference between using samples of concrete "about the size of a button" and scaling up to something the size of the foundation of a house.

And that just gets it to "buildable". To get to "ubiquitous" it also has to be cheap.

Use law.

See also:

"MIT engineers create an energy-storing supercapacitor from ancient materials", 85 comments, https://news.ycombinator.com/item?id=36951089

Ah yes, ancient materials, like graphene.

animals and other living things are sensitive to electrical charge in a way that we are not -- sounds more like a useful industrial application, not something to add to a home.

What about flood like situations?

I am curious, how does this material react to lightning? Does it overcharge and burn up or just stop storing power? One can test this with a long enamel coated wire and a model rocket on a stormy day to induce a lightning strike.

Why does the lightning hit the rocket instead of an antenna that's a lower height than the rocket?

Where does energy want to flow, to a higher concentration of energy or a lower concentration?

The lightning hits the enamel wire attached to the rocket and flows from positively charged earth to the negatively charged cloud. One can find videos of people doing this on youtube but I do not have any links handy.

I am more curious what this does to the concrete as it is not uncommon for lightning rods to be grounded to a grounding rod that is in the building's concrete foundation. I think this should be tested prior to mass adoption.

The grounding wire would just bypass the concrete into the earth.

This is not quite true. All ground rods have resistance and are supposed to be tested with a megger and documented to be below a specific ohm rating. With time they gain resistance and some of that energy will be induced into nearby objects, notably anything with electrical properties. In this case we are talking about a concrete that stores and conducts electricity. A lightning strike can be over 1,000,000,000 joules of energy. Some of that will be induced into that special concrete. Regular concrete can heat up and fracture which is mostly harmless but I would like to know what happens with this special concrete.

Well the article says it's made of material that wouldn't catch fire if that's what you're specifically Wondering.

Presumably smart people would be insulating the battery from an external surge like a lightning strike.

However in practical senses the lightning would go into the rest of the ground as the grounding wire would be bypassing the concrete.

My wife's coworker saw a cow go flying into the air last year when lightning struck nearby. Does lightning dissipate perfectly harmlessly when something taller is struck nearby? Actually curious

Generally yes because the taller person has lower resistance relative to the shorter person. So unless they're connected, lightning would pass through the person with the least resistance to the ground (easiest way to dissipate a voltage difference).

(Aside: https://practical.engineering just released a video on "Where Does Grounded Electricity Actually Go?" )

Proof he is a time traveler that reads HN. I enjoy his videos. Maybe he can play around with this concrete.

Electrified cement? LK-99? Where are the aliens. Who talked.

Is the idea here that there are actually two layers of cement separated by membrane? Or maybe more? Anything that breaks up the monolithic cement blob makes it worse at its primary job.

I guess, this would fail fail on any material properties we use cement for in various flavors of concrete in the first place. Also, the building material is concrete, not cement. Cement is just one ingredient.

(It's kind of sad that a publication like Science would mix these up. A road made from cement exclusively would be blown away in a minute. Cement is [just] a binding agent for the aggregate.)

FYI had you read the article, you'd see that they use cement/concrete accurately throughout, and are accurate in their usage of cement in the title.

One such quote, although it's throughout the article

> The problem is that cement, a primary ingredient in concrete, is normally a poor electrical conductor. So, in recent years, several groups have made structural supercapacitors by spiking cement with highly conductive forms of carbon, such as graphene or carbon nanotubes. Although these perform well, the ingredients are expensive and hard to produce in the massive volumes used in the cement industry, notes Franz-Josef Ulm, a civil engineer at the Massachusetts Institute of Technology (MIT).

But, how and why do you jump from what is to all assumptions an interesting surface material to building structures? Also, most capacitors are phono-sensitive, meaning they react to contraction and tension and all kind of vibrations, which wouldn't suggest load bearing masses as a prime candidate for this, even if the doping added to the cement didn't have any effect on the material properties. Let alone the practical problems of having significant charges in any structure, like a road or a building.

So here's some more article quotes lol

> Ulm and his team mixed a small percent of carbon black with cement powder and added water. The water readily combines with the cement. But because the particles of carbon black repel water, they tend to clump together, forming long interconnected tendrils within the hardening cement that act like a network of wires.

> Ulm and his colleagues cut this wired cement into small plates, creating supercapacitors 1 millimeter thick and 1 centimeter wide, about the size of a button. After adding a membrane, an electrolyte made from potassium chloride—a simple salt—and water, the researchers sealed the sandwich structure. When they then connected a wire to the plates and flipped a switch, cement supercapacitors lit up a series of LED lights.

> To succeed, researchers will need to scale up the button-size plates. Doing that isn’t trivial, Nguyen notes. As supercapacitors get larger their electrical conductivity typically declines, making it harder to inject and extract energy from them. One solution, Ulm notes, is to simply add more carbon black to the mix—but not so much that it weakens the structural integrity of the cement. For structural concrete, the researchers found they could add up to 10% carbon black without compromising too much of its strength. Ulm says the group has patented its technology and is now working to scale it up to match the output of a 12-volt car battery.

They are well aware of the concept of structural integrity and of course the big challenge is scaling up their idea in a way that does not compromise it.

It's somewhat hard to believe that this (forming lumps and adding membranes) does not affect the material properties as building material, especially, where various flavors of concrete are all about the grade of the cement. (Concrete isn't just concrete.) How is this, as a capacitor, immune to pressure? How do you jump from a 12V car battery to entire buildings and roads?

Retaining the structural strength of the cement itself does nothing about the fact that you've introduced a big lubricated slipface into the structure, namely the membrane.

Here's my best idea: You pour regular reinforced concrete in sort of a waffle pattern, make a bunch of capacitor cells in the holes, then put another layer of concrete on top. The individual membranes have limited shear stress. Leaks are isolated. Presumably cells of mostly concrete and water still have pretty good compressive strength, so maybe it will hold together like that. I'm guessing you at least have to increase the total slab thickness, though.

I'm guessing there will be some kind of creative architecture like that before it goes to prod, anyway.

I would think that the membranes would also be the reinforcement. Though I am not getting a good picture in my head from the description. It has to be practical. Mix concrete, pour concrete...the same way we do it now. There is roomm for skilled labor at the reinforcement phase which is a precision bit of construction that is inspected closely before pouring.

Yes, and the article didn’t touch upon that at all. Building a home foundation that would shake apart in a windstorm is a non-starter.

You could be hitting on something here. Instead of pouring monolithic you could use prefab blocks that are filled in. I have used that technique to repair a caved basement where cinder block replacements were filled with concrete and rebar.

There is a similar system using foam blocks that act as forms and are left in place. Menards sells them (and may own the manufacturer).

imagine your house catching random fire just like Lithium ion batteries sometimes do while you are asleep.

or some random dude (or a tree fall) punctures the wall of your house and sets it on fire

My electronics knowledge is extremely rusty; but don't capacitors discharge all at once? Every so often I see another article about using capacitors as batteries, but I've never seen one that addresses the discharge issue.

Capacitors do have a different discharge curve than batteries and this requires more sophisticated power management electronics but nothing too difficult. You basically need a power supply/regulator that can start with much less than rated input current and increase current draw as voltage drops to deliver a constant power output.

It takes time for them to discharge, and the rate they discharge can be controlled by the circuit, just like batteries. They just are much less limited in how much power they can handle, so they can discharge the same amount of energy faster. This is a feature, not a bug, as most applications need oversized batteries to handle peak power usage which is substantially higher than average.

You can just slap a resistor in series, which will induce a drop in potential over it. That, in turn, will mean the potential difference across the capacitor is lower, leading to a more shallow exponential decay of the current over the circuit - ie a slower discharge.

And that's just a passive circuit, with an active circuit you have a lot more options.

Note: I studied maths and computing so I could very well be wrong. I would appreciate being set straight by elec eng majors!

Conveniently, the energy density means that 1 cinderblock would hold approximately the same energy as 1 AA battery.

Man, that will turn my Walkman into a Lugman, no thanks, future science.

So you could plug in a LED fixture directly to a powered wall block and run overnight, charged by solar fixed to same wall during the day.

The is one of the biggest technological innovations I have ever read.

That will promptly be debunked like solar roadways, etc by thunferf00t and others ;)

chasing bugs about to enter at a totally new level in the history of computers

They mention roadways, which makes me wonder: Given that this has so much carbon black in it how much more solar energy would it absorb that would normally be reflected. Not many pictures but the samples look quite dark: https://www.pnas.org/doi/full/10.1073/pnas.2304318120

How practical this would be? Considering use cases of reinforced concrete and like? Or how sound structurally it would be compared to what we currently use? We use reinforced concrete for reasons. And if this stops it from working is it really worth the effort?

Dumb question (please don't mad)

Why don't we put springs under massive buildings like skyscrapers that anyway move a little bit with wind?

Maybe the millions of tons compressing the springs a little bit could result in some electricity?

Or under roads and airport tarmac?

For the swaying buildings, you'd almost certainly not get enough power out of it to make it worth the cost and additional complexity to install.

For roads, whatever power you generate from the traffic would be less than the additional power those cars require to drive on your road. It would be a net loss. Basically generating electricity from gasoline, with extra steps.

Shouldn't moderators remove this? This is not /r/upliftingnews or /r/futurology.

I know I'm being grumpy and highly skeptical, and that Y combinator is about innovation, but why not make a hackernews to compartmentalize those things?

I would be okay about a paper that discuss feasibility instead of the usual "maybe yes? maybe no." blogspam.

HN's only criterion is whether something is intellectually interesting. I don't see why we should remove this one - but I do think the baity title could be replaced (this is in the site guidelines: https://news.ycombinator.com/newsguidelines.html), so I've replaced it with a more representative sentence from the article.

> electrified roadways could power electric cars as they drive

Here we go again, SolarRoads…

The article is all hype.[1] The paper isn't much better. There's a bullshit "Significance" section at the top. Most of the "references" are to generic papers about energy. If there's a watt-hours/kilogram value, the number that matters, I can't find it. Here are Wh/Kg values for known ultracapacitors.[2] Numbers are in the 4 to 15 range. Where is this new thing?

[1] https://www.pnas.org/doi/10.1073/pnas.2304318120

[2] https://en.wikipedia.org/wiki/Supercapacitor