With Fungi in the Mix, Concrete Can Fill Its Own Cracks | Hacker News Reader

With Fungi in the Mix, Concrete Can Fill Its Own Cracks

smithsonianmag.com

139 pointsbryanrasmussen44 comments

Or perhaps we could go back to using lime[0], which has long been known to be naturally self-healing[1], and has been used throughout history to build structures that (literally) stand the test of time[3]. And let's not forget: considerably less CO2 emissions during its lifetime[4].

[1] https://en.wikipedia.org/wiki/Lime_mortar

[2] Self-healing of lime based mortars: microscopy observations on case studies https://repository.tudelft.nl/islandora/object/uuid:ff226ad0...

[3] https://en.wikipedia.org/wiki/Lime_(material)#Roman_concrete

[4] http://ecolime.co.uk/c02-quick-facts/

I thought the secret of Roman concrete was the Tufa, a pyroclastic sand, which was used, for instance, in the construction of the Port of Ostia. This civic work has 2000 year old concrete that's intact and in direct content with the sea water.

I thought it was the use of pozzolana--glassy aluminosilicate volcanic ash--along with lime. The Roman marine concrete may also have an advantage from being mixed with seawater. It gets stronger in saltwater. Portland cement concrete with iron rebar gets weaker in seawater, because the rebar swells and makes the concrete spall off.

Although it is true that sand from different geologic deposits can show vastly different results when used in the same building product. Superior binder plus superior aggregate could make superior concrete.

I think there is a fair amount of interest in pozzolana type cements because it's becoming apparent that portland cement + rebar has a finite life.

> sand from different geologic deposits can show vastly different results

That's the other bugaboo about portland cement, Aggregate expansion/alkali-silica reaction/concrete cancer. They used the wrong type of aggregate and dune sand in the old foundation of my house (rental not my problem unless I'm in it during the next earthquake). So now it's crumbling.

Granted if you keep reinforced portland cement dry, it's fine. Otherwise eventually it'll fail.

All three of you above are right, I believe.

And I don't see why we couldn't add fungi to this mix. Along with Titanium Dioxide:

https://www.sciencedirect.com/science/article/pii/S095006181... [check the citing papers: https://scholar.google.com/scholar?cites=1362107164675591553...]

And also, we have polymer based cement nowadays:

https://www.sciencedirect.com/science/article/pii/S016943321...

The "Journal of Materials in Civil Engineering" back in 2013 had a special issue on "Materials Innovations for Sustainable Infrastructure":

https://ascelibrary.org/toc/jmcee7/25/7

And here's a 2017 "Review on Characterization and Mechanical Performance of Self-cleaning Concrete":

https://www.matec-conferences.org/articles/matecconf/abs/201...

In addition to this, here's a 2008 article from MIT Technology Review on concrete specifically designed to capture somewhat absurd amounts of CO2:

https://www.technologyreview.com/s/410499/a-concrete-fix-to-...

And then there's this whole glow in the dark concrete business:

https://edition.cnn.com/style/article/glow-in-the-dark-cemen...

The highly inovative thing about this glow in the dark cement isn't that it glows in the dark - it's the fact that it's UV condusive, similar to translucent concrete:

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

And this distinguishes it from the much older glow stone concrete tech, marketed by companies like Ambient Glow Tech:

https://ambientglowtechnology.com

...Core Glow:

https://www.coregravel.ca/core-decor/core-glow/

And many other companies. Although that kind of stuff also seems really really nice.

There's also LiTraCon, which adds optical fibers to the mix:

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

Like many fields of science, material science seems to have become absolutely crazy in the last two decades with a huge swath of research, so much of it that nobody actually manages/bothers to combine all the disparat and different discoveries into one huge gigantic leap. Instead you get special materials A to Z, each with their own special flavor. It seems highly likely that ~7±2 years from now, someone will come along and do so, synthesizing the majority of these discoveries into one bigass leap in material science. If it hasn't happened already in someone's head and we'll find their paper on arxiv later this year. I'd speculate this will likely come out of either India or China, as western patent laws would make any such leaps-and-bounds innovations absurdly expensive with gigantic patent wars happening. Whereas if China or India suddendly start using concrete of this kind inside their own countries only, what you gonna do about it to stop them? Sue them? Watch either of them give negative shits. (I could see this becoming problematic with China and their massive road construction in Africa tho.)

To provide some additional future speculation:

It seems likely to me that this will then lead a pseudo-revival of Brutalist architecture, but modified by knowledge we have today, with structures appearing, paradoxically, as both more organically rounded (hence the pseudo-, since that won't match the Brutalist style) AND more synthetically jagged.

I say this because:

1. It seems almost certain to me that any such 'new concrete' would end up a lot less grey than Portland cement, if you look at Roman concrete as an example, both normal Roman concrete and Roman marine concrete have a color significantly less grey than normal Portland concrete. Adding Titanium dioxide and other materials innovations to that would likely shift this further into a more white-ish hue.

2. It seems highly likely to me that they'll modify the Trichoderma reesei from the parent article to include bioluminescence. Likely for the purpose of making it easily tracable in the concrete as part of research. And then someone in the lab will go "wow that looks pretty". Combine this with what I've already pointed out and you'll get very crazy looking buildings.

3. We know a lot more about the geometry of architecture than we did in the last century. For examples, see here:

* https://en.wikipedia.org/wiki/Plastic_number

* https://link.springer.com/article/10.1007/s00004-015-0285-1

* https://www.researchgate.net/profile/Francisco_Javier_Roldan...

* Everything ever done by Christopher Alexander (https://en.wikipedia.org/wiki/Christopher_Alexander)

And many more reason I don't have the capacity to go into right now, consider this only the tip of a very large iceberg.

Also survivorship bias? The only remaining Roman concrete is the stuff that for whatever reason has lasted until today.

A lot of Roman concrete has lasted to this day. The aqueducts are still impressive, the colosseum is only 2/3 standing because of an earthquake hundreds of years ago (and is otherwise a fine museum), and the pantheon is as shockingly gorgeous today as when it was built 2000 years ago.

Totally agree, but just wanted to expand on the colosseum for a moment. While traveling there, I spent a full day at the Roman Colosseum. Its outer travertine stones were all without mortar and originally held together with numerous iron clamps. Since the fall of Rome, the clamps were slowly harvested, leaving the surface of nearly every outer stone with huge holes. In the opinion of those I spoke with, had the structure been left intact with it's clamps, it would have endured in much better shape.

Pantheon is one of the world's greatest buildings, but not because of concrete. And it has been repaired.....a lot.

It's not survivorship bias because no one claimed that all Roman concrete was better than all modern concrete.

The point is that the vast majority of modern concrete, especially using rebar, will last decades compared to some Roman concrete, which has lasted millenia.

I thought the secret to the life of Roman concrete was the fact that it does have rebar.

You mean doesn't.

The wikipedia article above indicates that the durability of aquatic roman concrete is the result of a reaction between the lime and tufa

>The seawater instantly triggered an exothermic chemical reaction. The lime was hydrated – incorporating water molecules into its structure – and reacted with the ash to cement the whole mixture together.

Quick lime is also known as burnt lime. It is not found, it is produced. The production of burned lime produces CO2. Lots of it.

CACO3 -> CAO + CO2

Plus the CO2 released by fuel used in the burning process.

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

Lime mortar/plaster cures by absorption of CO2, from air: http://www.britishlime.org/education/lime_cycle.php

Set up farms around the plant.

As explained in the reference given, nearly all of the CO₂ is reabsorbed when the lime sets, while portland cement reabsorbs a smaller proportion of the CO₂ generated.

Isn't cement mostly lime?

I for one would love to see something like this happen, but I think ultimately this will always be limited to niche applications.

A developer recently built a 20 story apartment building next to my office window using entirely a reinforced concrete frame. I was incensed to find out that because of "concrete cancer" [1], the lifespan of that building may be less than 70 years. But the more I thought about it, the more I began to believe that maybe the additional lifespan is not an asset. The building is attractive today, but might not (probably won't) appeal to people 40 years from now. Furthermore, buyers are going to want different things from their homes (look at the popularity of open kitchens 40 years ago vs now). And I began to realize that it would be quite difficult to design and build a building that would be useful beyond 70 years from now.

Another way to look at it is that the marginal value of 10 years of longevity is not that large out 80-90 years. I think you'd have a difficult time finding a developer who would pay 10% extra to get a building that lasts 100 years instead of 90.

This line of reasoning leads to an icky "planned obsolescence" approach, but I think these are the economic realities.

[1] http://www.remedial.com.au/structural-repairs/concrete-cance...

You might want to Google Images for Brasília (Brazil's capital), built in the 50's with godzilions of reinforced concrete. It's still spectacular but it's high maintenance and you can see concrete cancer everywhere. I'm not sure if it was a good idea to use it there but surely it is gorgeous due to the architectural possibilities of reinforced concrete.

A properly designed concrete structure will include enough clear cover (that is the distance between the surface and the reinforcement) to avoid water reaching the reinforcement. It should also take precautions such as roofing to avoid water interacting with the concrete in the first place.

LEED certification includes a credit called "good bones" which recognizes that although exterior trends change, the concrete bulk of a building can be reused if kept in good condition. A new facade can completely rejuvinate an otherwise dated structure. Most concrete building construction focuses on creating large open floors with columns to provide the largest flexibility in floor plan.

An additional interesting trend I've been seeing in Chinese construction is the construction of structures with double the standard height between floors. These buildings can be finished with units with features such as high ceilings and loft spaces that most high-rise units cannot accommodate.

That's good context, thanks. We're quite near a salt water estuary here, I imagine the humidity and salt in the air also makes a difference...

Another thing you can do relatively cheaply (I think) is powered cathodic protection. I don't know if they bothered to do that on this building.

It's not always the reinforcement. It can also be the accumulated result of decades of very slow reactions happening in the cement binder, or between the binder and the aggregate, generally also driven by moisture and gases penetrating the pores in the concrete, so cracks and spalling accelerate the process.

If it was just the rebar, we could replace the iron rebar with drawn basalt fiber rebar.

Perhaps in the future, structural concrete will be covered in an outer layer of ceramic that is subsequently vitrified at a certain stage in curing. You keep your building from collapsing by burning it in a towering inferno first.

As someone who lives in a building that is 70 years old, I can tell you pipes (brass?) only last about 70 years.. redoing piping in place is a major pain. If the location wasn't so good I'd be gone long ago..

I believe copper piping is most-common, it's always the first thing building-site thieves go for!

Pipes can last centuries or only years, depending on the material, the temperature, and the solutes in the water — even without getting into cases where the pipes actually break. Both lead and copper (which is more common than brass!) can last centuries in cold water that isn't chemically aggressive. Heck, in Boston a few years back, they dug up some wood pipes that were installed in the 1700s.

We tore our house apart somewhat about eight years ago and had all the pipe work replaced, amongst other things. We also (I did this bit because builder/plumbers generally take the path of least resistance) removed the last two lots of re-plumbing. The house was built in the '20s which is pretty modern hereabouts.

Brass is unlikely, copper is the material. The oldest pipe work I found was steel in our place - it was hard and weighed a fair bit. Copper is maleable, easy to bend and braze joints on to. It does corrode eventually but I think the thin layer of copper oxide that forms then seals in the pure copper, protecting it. The longevity of copper can be seen in the green roofs of some churches which must have looked absolutely stunning before oxidizing.

AFAIK pipes are usually replaced every 50 years. That's the common timespan around here at least. And yeah it's expensive.

As an example, here's a strange eyesore on an otherwise nice landscape that probably looked futuristic or something back when it was made, the concrete square tower to the right of the turquoise pyramid thing. http://www.newpaltz.edu/media/stock-images/slides/12308197_9...

That may just be a dormant Vogon spaceship.

Stranger Things

It seems that the term "Concrete Cancer" has been somewhat watered down since I studied Civ Eng at Plymouth Polytechnic (Devon, UK) in '89-91. I think you are referring to spalling.

It was a while back but I recall that the characteristic map cracking and eventual failure need salty water as well as the correct chemical composition of the cement used. I think there are something like three conditions needed. Stop one and you fix the problem. I seem to also recall that PP's Civ Eng dept did a lot of work on this in the '80s. Plymouth is a sea side city and has a lot of concrete structures that suffered eg Charles Cross multistory car park.

To be honest I would find it hard to believe that a structure that size would be designed to that short time scale. I'm not familiar with Aussie building regs (I'm not familiar with anyone's outside the UK and saw a.com.au link!) but it would be very hard to design for so short a lifespan. There will be a minimum conc. depth to the reinforcing bars, just for fire regs, let alone spalling. If the weather is a bit fierce then the other design criteria like being able to withstand a 1 in 100 or 200 or whatever year event will also play a part in the lifespan. Obviously there will also be a factor of safety applied which could be as high as 1.4. Take a close look at the final finish, it may have been sealed in some way. Keep the water and freeze/thaw and the like away and conc. can last a bloody long time.

70... 80-90... 100...

I think you're both right and wrong :)

You're right in that certain buyers are going to be looking for certain elements that might not make much sense from a long-standing building point of view. Architectural shapes and trends change over time.

On the other hand, its also true that a lot of these trends are just bad architectural design. Period.

Sunken lounges of the 70's. Media-rooms and conspicuous consumpition-esque cavernous entrances and questionable elements in macmansions. These are designs that are incredibly difficult to repurpose into anything but their original purpose.

In my country (Aus), there is a now a common suburban design that almost entirely ignores long term elements and lessons of the environment that have been known for at least 100 years: see https://en.wikipedia.org/wiki/Queenslander_(architecture). Now we have a poor relation of the generic american style: dark roofs and colours, no overhangs/shelter/verandahs, directly western facing living areas and frontages, all designed to maximize internal sq meters/price.

Now, i appreciate that my queenslander example is a style built of wood traditionally. But there is another style example of highly valued real-estate with long term potential in the urban centres: victorian terraces and townhouses. Aside from the regrettable wealth signaling effect of owning one, its an architectural form that has lasted the test of time and is arguably constructible via concrete. And one of the reasons it has done so is because that form is the complete opposite of the media room/sunken lounge/mcmansion: almost universally flexible and readjustable. A proper Victorian townhouse in its context can be reclaimed and used as a bar, as a restaurant, as a residence, as an office or a place of business. Though like all succesful architecture, this is only because it works in the context of its environment.

Which means my investment in the property will only last what? 50 Years?

I find it funny that one of the sub-plots of Wolfenstein: The New Order is sabotaging Nazi super concrete using fungi implanted in the mix at the factory.

The article glosses over how the spores could expect to respond during the highly saturated setting phase. It is reasonable to assume they could cause deformations or web-like weak points in new concrete by being too active well before they are intended to be active. I think getting a predictable outcome during setting is probably the challenge.

I never understood why our isn't aerated concrete more popular in the US.its lighter and insulates heat and noise so much better.

Probably more expensive and less strong

Insulation is not as easy to achieve once you consider structure framing in poured concrete, and humidity load (AAC is very permeable to moisture).

http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/...

There is a waterproofing product called xypex that coats concrete. When you get it wet its crystalline structure grows to fill cracks. It sounds similar to what the article talks about. It looks good as well so if youre building a house consider using it instead of the black tar typically coating a foundation.

Article from 2017 on same subject https://www.technologyreview.com/s/608717/how-mushrooms-coul...

Similar process with bacteria rather than fungus from 3 years ago http://www.cnn.com/2015/05/14/tech/bioconcrete-delft-jonkers...

As they grow, they’ll work as a catalyst within the calcium-rich conditions of the concrete to promote precipitation of calcium carbonate crystals. These mineral deposits can fill in the cracks.

Pure calcium carbonate is not as strong as concrete. It sounds like this will just fill in cracks with weaker material, hiding them from inspection, which would be even worse --- the strength of the material is degrading but not visibly.

Still just an idea; not ever been tried apparently.

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