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Just because the brick is able to withstand throwing it on the rocks doesn't mean it is not going to deform under load. Brick strength is measured in ability t

Just because the brick is able to withstand throwing it on the rocks doesn't mean it is not going to deform under load. Brick strength is measured in ability to withstand deformation under load and as far as I know there isn't any popular "plastic" that can do comparably. For a single story house this probably doesn't make any difference, but for a larger structure the load could cause bricks to loose shape, creep and cause the structure to fail. Also, plastics tend to get soft rapidly at temperatures. I don't think plastic bricks exposed to sun (Kenya?) would fare for long. Another issue is that plastics tend to deteriorate in UV. That could be fixed with a good paint but it also costs. (Edit: for the pavement this is horrible idea as the plastic is going to be broken down and dispersed in environment in large amounts)

jay_kyburz 6y ago
I only skimmed the article, but I thought they were just pavers. (For making a path). Buy yes, I came to say something similar, if you just compress the plastic into a block and lay it down to make a path then as it deteriorates surly you are just contaminating your environment with mico-plastic particles.
- londons_explore 6y ago
  Ssssh... People prefer to distribute their problem into invisible pieces put into the environment slowly over 1000 years than to just bite the bullet and incinerate plastics that have reached their usable lifespan...
  - smeyer 6y ago
    There are real reasons to not want microplastics in your local environment, but I think your dismissiveness of spreading a problem out over 1,000 years is unwarranted. There is a huge difference between a problem that has to be solved in a year and a problem that has to be solved in 100 or 1,000 years, because time is an incredibly valuable asset. Delaying some of the carbon we put in the atmosphere for hundreds of years is massively useful, because it buys us time to try stave off and ameliorate some of the effects of climate change.
    - arcticbull 6y ago
      Fair but you can also simply bury the compressed bricks yeah? Recycling plastic has always been a ploy by the oil industry to increase consumption and make people feel good about the product. Burying the compressed bricks is actually a great way to handle sequestration. [1] https://www.npr.org/2020/09/11/897692090/how-big-oil-misled-the-public-into-believing-plastic-would-be-recycled https://www.npr.org/2020/09/11/897692090/how-big-oil-misled-...
      - unloco 6y ago
        well, that pretty much describes a landfill. I've always wondered if they couldn't compress it, like those bricks but cubes, then use those cubes mixed with base fill dirt for building bridges and such. Like the massive earthworks they build around highways and such.
      - cptskippy 6y ago
        This isn't a ploy, it's a feel good puff piece about someone finding a use for the wasted they're swimming in. A plastic paver walk way is nicer than a muddy path littered with plastic refuse.
        arcticbull 6y ago
        I didn't suggest this was a ploy, I'm confident that the person in question has only the best intentions. I don't think it's unfair to step back and ask what the right approach is, intentions aren't always enough. For instance, the issue with flammability/melting and also microplastics contamination is real and worth asking. I wonder if using these bricks as building foundations or something might not be a good way of solving both problems at once. However, that's an idea that would only arise if we ask pressing questions in the first place.
        cptskippy 6y ago
        It's not the ideal building material and it's a plentiful resource that would otherwise end up ideally in a landfill but likely along the side of the road. From their perspective it is a good use of something that might otherwise be litter.
  - notjtrig 6y ago
    'The best solution to pollution is dilution'
  - imtringued 6y ago
    Why do you advocate for CO2 pollution? Capturing that CO2 suffers from the exact same problem. You either pump it into sealed caverns and hope they don't leak or somehow extract the carbon and turn it into a solid. In the end you are "landfilling" the CO2 instead. Why not skip the middle man and just bury it directly?
- robotnikman 6y ago
  The microplastics which we don't see always comes to my mind when I see plastic reused in ways such as this. Though it probably does depend on the type of plastic, but I'm no chemist.
  - lmilcin 6y ago
    This is plastic that would go to landfill. Expect it to contain just about everything. I don't expect this to be heavily processed. More like melted together with some additions.
  - Puts 6y ago
    Microplastics is a huge problem, BUT I can't imagine this being worse than things like tiers and shoe soles.
- kaycebasques 6y ago
  > if you just compress the plastic into a block and lay it down to make a path then as it deteriorates surly you are just contaminating your environment with mico-plastic particles The article says that the plastic is mixed with sand, heated, and then compressed into bricks. Given this, is your comment still valid? Honest question, I'm not a material science person.
  - dogma1138 6y ago
    Yes, the plastic in this case acts as a binder, in fact it would potentially be worse since the heating likely evaporated or decomposed most of the plasticizer which would make the plastic more brittle and more likely to wear off into micro plastics.
  - cptskippy 6y ago
    Someone mentioned that the pavers are made from plastic bottles that already deteriorate and shed microplastics into the environment. At least in dense brick form the surface area is dramatically reduced and the deterioration rate slowed.
- djrogers 6y ago
  The alternative is to throw all of this plastic into a landfill where it will… leach into the soil and contaminate the environment with plastic particles. At least this option stabilizes the plastic for a period of time.
  - jay_kyburz 6y ago
    I would have thought dumping the plastic in a deep pit, perhaps with some kind of solid lining would slow/prevent the plastics breaking down into "micro particles" (whatever they are) and ending up in our food.
  - Nasrudith 6y ago
    Ironically most proper landfills (at least in the first world) use plastic liners along with clay as part of their barriers to prevent water contamination from other trash. I am no expert - so I cannot say if the barriers put plastic in the groundwater but that method prevents more acute toxins like dioxins and oil from getting in.
kaycebasques 6y ago
> Just because the brick is able to withstand throwing it on the rocks doesn't mean it is not going to deform under load. The end of the article says they founded in 2017 and have recycled 20 tons of waste. Maybe structural issues will emerge after 5+ years of use but it sounds like this approach has already had a fair amount of real-world usage.
- dmurray 6y ago
  20 tons - enough to build what, 1-10 houses over 3 years? - doesn't sound like it's been tested at scale to me.
  - hn_throwaway_99 6y ago
    I'm still confused why there is so much discussion in the comments around using these bricks in buildings. The video is pretty clear about them being used as pavers.
- LegitShady 6y ago
  Most likely not - stuff will just fall down and nobody will talk about it. I'm sure the bricks they made in 2017 that actually see any load are already seriously deformed from creep/cold flow.
robocat 6y ago
You wouldn’t use plastic bricks for building without either serious fire risks. A non-flammable coating on the brick could potentially be developed, but not easily and perhaps not cost effectively. This is what happens when you use polyethylene as part of your building: https://www.bbc.com/news/uk-40301289 https://www.bbc.com/news/uk-40301289
- labawi 6y ago
  The bricks contain polyethylene, but a large part, probably most of it, is sand. Also, it is not foam in enclosed spaces, but a full hard material. A non-flammable coating would perhaps be a layer of plaster or paint? I think you are seriously overestimating the flammability of the product. Have you seen rooms with vinyl floors, PVC windows, foam / fake leather couches? Each of those will burn more easily a viciously than the bricks. My concern would be with possible structural failure at high temperatures and some fires may be able to pass through walls of these bricks. However, I don't think they are building apartment buildings from these bricks.
  - robocat 6y ago
    From article: “In his report to the public inquiry, Professor Luke Bisby said evidence ‘strongly supports’ the theory that the polyethylene material in the cladding was the primary cause of the fire's spread.” and “The ACM (aluminium composite material) product on Grenfell Tower incorporates a highly combustible polyethylene polymer filler which melts, drips, and flows at elevated temperature.”. I am not a materials engineer, but it looks to me that bricks with more than 10% of polyethylene are likely to be flammable in the case of a house fire. I don’t know whether the Grenfell tower cladding had filler, but it is common for the polyethylene core to be mixed with filler within the cladding to help protect against fire, for example the ALPOLIC A2 product mentioned in [1] has an image showing a table with: ALPOLIC fr: Combustible ingredients < 30%. < 13 MJ/kg ALPOLIC A2: Combustible ingredients < 10%. < 3 MJ/kg And [1] says “Its calorific value is given as something less than 13 MJ/kg, more than four times the value considered to be of ‘limited combustibility’ in the UK”. Above facts are why I think even a large percentage of sand might still leave flammable bricks (polyethylene is like solid petroleum, until it melts and behaves more like a liquid or wax with a viscosity depending on multiple factors). [1] http://theriveroflife.com/2018/02/08/grenfell-tower-is-the-core-of-acm-panels-a-filler-material/ http://theriveroflife.com/2018/02/08/grenfell-tower-is-the-c...
lhorie 6y ago
Not a structural engineer, but I thought that the beams are the load bearers, while the bricks are more of less just filling vertical space. I think another interesting point to consider is cost. I watched a video a while back about a premise of using plastics for building roads, and in addition to the deformation/UV deterioration issues being brought up, another issue that was brought up was that concrete is cheaper than even the lowest quality recycled plastic.
- londons_explore 6y ago
  > the load bearers, while the bricks are more of less just filling vertical space Bricks are decorative in a few buildings, but this is by far the minority. Where bricks are used in < 8 floor high buildings, they normally are supporting the weight of the entire structure.
  - dylan604 6y ago
    Where do you live that a building of modern construction is supported by bricks? In the US, multi-story residences are built on wood with a brick facade. Multi-story commercial buildings are built using wood up to 4 stories (depending on locale), and steel after that.
    - lmilcin 6y ago
      I live in Poland. Almost all buildings outside cities are bricks with bricks being load-bearing. In cities, almost all buildings older than 1950 are also made from bricks.
    - londons_explore 6y ago
      The US is the odd one out... I completely see why you'd make a temporary building out of wood so that you can build it in just a few days. But if this is a house, expected to last 150 years plus, and you're already bringing lots of bricks to the site, you really ought to be using the bricks to hold the building up and reserving the wood for the internal floors and other things that will be replaced every 75 years.
dylan604 6y ago
There are plenty of uses of bricks that do not need to support the weight of a multi-story buildings. Just because an item doesn't fit for a particular use does not mean it is not a viable solution for other things. Paving stones, mailboxes, retaining walls, etc are all examples. I for one can appreciate that someone is taking effort to resuse/recycle plastic trash into something useful like this. Maybe rather than shitting all over something for a use it's not necessarily intended for, maybe try to think of other uses this kind of innovative processing can be improved would be much more productive.
- lmilcin 6y ago
  Of course there are uses. I am even very happy people try to re-use what would normally be put to waste (unless it causes more plastic to disperse in environment). Just don't claim it is "stronger" than regular brick if that is not true.
- silicon2401 6y ago
  > Maybe rather than shitting all over something for a use it's not necessarily intended for, maybe try to think of other uses this kind of innovative processing can be improved would be much more productive. Not a very constructive response. Do you have any counterpoints to the other user's points, or do you just not allow people to point out potential issues with materials that may be used for human housing? Progress requires a balance between some people focusing on achievements and some pointing out the things that can still be improved. If I were going to rely on a new material, I'd definitely want its issues to be pointed out and addressed first, rather than just jump to using it.
  - deleted 6y ago
    [deleted]
  - kristo 6y ago
    There is a little thing called tone. And criticizing someone’s over negativity is constructive. You’d want that negativity problem to point pointed out and addressed, wouldn’t you?
gumby 6y ago
> Brick strength is measured in ability to withstand deformation under load and as far as I know there isn't any popular "plastic" that can do comparably. By definition something plastic will deform, else it wouldn't be plastic! A "rigid plastic" would be like a "miniature giant"
- dogma1138 6y ago
  The plasticity in their name refers to the plasticity during manufacturing which means they can be easily shaped or molded. In their usable form plastics have varying modes of failure depending on their material properties, many of them do not deform at all under stress but rather shatter just like glass.
- lmilcin 6y ago
  In this case the world "plastic" is used in its popular sense. Vast majority of "plastics" are plastic in physical sense. But some are not. Some undergo physical or chemical change after they are cooled and are on longer plastic in the physical sense. So maybe not "by definition".
- deleted 6y ago
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ineptech 6y ago
> ...this is horrible idea as the plastic is going to be broken down and dispersed in environment in large amounts This take seems trivially and obviously wrong. Recycling plastic produces a lot of nasty chemicals and is awful for the environment, but we still do it, because the alternative (chucking it in a landfill) is worse. The question is not whether these plastic bricks are bad in absolute terms, it is whether they're worse than whatever was being done with Kenya's plastic waste before this woman came along. However, it is curiously common. From elsewhere in this thread: > What about leaching [sic] chemicals into the soil and groundwater? > I do wonder about microplastics flaking off of them, though.... > ...making me concerned about plastic particulate being released... > What happens when these erode - wouldn’t plastic particles contaminate water? > ...how does this product not heavily pollute the environment? Isn't that interesting? Not to sound preachy, but did anyone have the "wait isn't this bad for the environment" reaction to any of the other stories on HN today? Starlink? That new Samsung fab plant? Shit, there's an ad on the front page right now for a gourmet dinner delivery startup. What is it about this one that brings out HN's inner environmentalist?
- LockAndLol 6y ago
  > What is it about this one that brings out HN's inner environmentalist? This is obvious and very easy to see, while the other examples you brought up aren't. Your examples might even be doing more damage, but because the end result is shiny, people are distracted. Plus, I'm sure there's a part of first world vs third world prejudice: "she's probably uneducated and doesn't know what she's doing, plus her accent sounds that way".
- Bakary 6y ago
  >Not to sound preachy, but did anyone have the "wait isn't this bad for the environment" reaction to any of the other stories on HN today? Starlink? That new Samsung fab plant? Shit, there's an ad on the front page right now for a gourmet dinner delivery startup. What is it about this one that brings out HN's inner environmentalist? This is one aspect of the tech world (and more broadly the "comfortable knowledge worker" class) that irritates me. There are so many aspects of sustainable development that are only considered from a perspective of NIMBYism mixed with orientalism. The one that bothers me the most is the portrayal of overpopulation as something caused only by people in developing countries, as if the first world wasn't part of the total count.
darth_avocado 6y ago
Fun fact: most unrecycled plastic waste (majority of plastic) from ends up in one of the two places: landfills or the oceans. It is already breaking down and leaching into the environment. I see this as an absolute win unless we stop using plastics altogether.
Clewza313 6y ago
Based on the shape and the pricing per square metre, it looks like the primary use case is for pavement. As for being a "horrible idea", this is what happens to plastic today in the slums of Nairobi: https://media.gettyimages.com/photos/kibera-slum-nairobi-picture-id184229060 https://media.gettyimages.com/photos/kibera-slum-nairobi-pic... Even if the bricks leach a bit, it's still much better than the status quo of soaking individual plastic bags in sewage for years.
tyingq 6y ago
Their website mentions "Ideally most suitable for parking areas not commonly frequented by heavy trucks" on their heaviest duty brick. So they seem to be aware. They only reference use as pavers. https://gjenge.co.ke/our-products/ https://gjenge.co.ke/our-products/
napier 6y ago
I like these kind of stories. Recycling or waste management infrastructure in many countries doesn’t cope well with plastic waste. And many countries that do a good job of collection send bales back to Asia in return trip shipping containers where much of it ultimately ends up fueling coal power stations or the fate described below. Bricks with plastic binder aren’t perfect; leachate and durability under load and abrasion are issues to be aware of. But the alternative and predominant plastic disposal method in this and similar contexts is dumping in a ditch, in a field or in an unsealed ad hoc landfill at best, or more probably burning in a heap with whatever fallen leaves and other garbage there is that’s remotely flammable. Which results in a toxic chemical smog that persistently contaminates the air, soil and water.
IanSanders 6y ago
These bricks could fill a portion of space within another substance - concrete? to reduce the amount of the latter required.
mnw21cam 6y ago
> Also, plastics tend to get soft rapidly at temperatures. I don't think plastic bricks exposed to sun (Kenya?) would fare for long. Yeah, it can get hot in parts of Kenya. But this is in Nairobi, which is somewhat elevated, and doesn't get too hot at all.
throwaway316943 6y ago
My father actually ran a plastic waste recycling business similar to this about 20 years ago. He didn’t add any filler to the plastic so it was just ground up and run through an extruded and then injected into moulds. He mostly made beams and boards. The business didn’t survive but we still have a number of the plastic boards and beams. They’ve been in continuous use on his property for the past two decades in various incarnations as fencing, shed walls, sleepers used for keeping material off the ground, etc. They haven’t degraded as far as I can tell although they might be slightly lighter in colour. Only some of the 2x6 boards deformed and broke when they were used as a fence but I think that has more to due with livestock pushing up against them. These bricks will probably work fine as foot paths, the sand and dye in them will slow UV degradation and foot traffic is unlikely to wear them much. I wouldn’t build a house out of them, offgassing would be a bigger concern for me than sagging, at least on a 1 story structure. A brick is a widely useful thing so I hope her business does well. She’s essentially just making plastic composite which is something you’re seeing in North America now used for decking.
okal 6y ago
She's a materials scientist. I'd wager that she's considered all of these factors. She's also been doing this for a while, and produced tonnes (literally) of these for, if I read correctly, a year and a half. Maybe consider that she's thought through this?
- darksaints 6y ago
  Of course she has. In fact she indirectly confirms that the common misconceptions regurgitated about plastic do not apply here. She takes the plastic that cannot be recycled using typical methods. The reason why some types of plastic cannot be recycled is because they cannot be melted. This is true of all thermoset plastics, and it is practically true of some thermoplastics as well (at least after they have been repurposed a couple times). The only way they could be softened enough to bind with sand is by softening them in an environment with high enough pressure and temperature, but devoid of oxygen (otherwise they'd just burn). And even if they were using melty thermoplastics, the properties will still change drastically the moment you introduce a substrate like sand or gravel and turn it into a composite. Just like how there is a massive difference between pure Portland cement (extremely brittle, with almost no load-bearing capability) and concrete, which is a composite. Nobody seems to regurgitate these rubbish misconceptions about plastic when talking about carbon fiber composites (which are held together by plastic!). I don't think I'll ever understand the techie's tendency to think they know more about certain fields than specialists that work in those fields.
tgtweak 6y ago
The plastic acts like a rebar, allowing the brick to absorb and mitigate fractures that would ordinarily crack the brick and compromise it's integrity. They would not have the same compressive strength as a cement brick, but would likely fare far better for use cases like pavers and retaining walls. I would imagine they perform better in earthquake situations and may have longer longevity than steel rebar enforced concrete.

jay_kyburz 6y ago

I only skimmed the article, but I thought they were just pavers. (For making a path). Buy yes, I came to say something similar, if you just compress the plastic into a block and lay it down to make a path then as it deteriorates surly you are just contaminating your environment with mico-plastic particles.

londons_explore 6y ago
Ssssh... People prefer to distribute their problem into invisible pieces put into the environment slowly over 1000 years than to just bite the bullet and incinerate plastics that have reached their usable lifespan...
- smeyer 6y ago
  There are real reasons to not want microplastics in your local environment, but I think your dismissiveness of spreading a problem out over 1,000 years is unwarranted. There is a huge difference between a problem that has to be solved in a year and a problem that has to be solved in 100 or 1,000 years, because time is an incredibly valuable asset. Delaying some of the carbon we put in the atmosphere for hundreds of years is massively useful, because it buys us time to try stave off and ameliorate some of the effects of climate change.
  - arcticbull 6y ago
    Fair but you can also simply bury the compressed bricks yeah? Recycling plastic has always been a ploy by the oil industry to increase consumption and make people feel good about the product. Burying the compressed bricks is actually a great way to handle sequestration. [1] https://www.npr.org/2020/09/11/897692090/how-big-oil-misled-the-public-into-believing-plastic-would-be-recycled https://www.npr.org/2020/09/11/897692090/how-big-oil-misled-...
    - unloco 6y ago
      well, that pretty much describes a landfill. I've always wondered if they couldn't compress it, like those bricks but cubes, then use those cubes mixed with base fill dirt for building bridges and such. Like the massive earthworks they build around highways and such.
    - cptskippy 6y ago
      This isn't a ploy, it's a feel good puff piece about someone finding a use for the wasted they're swimming in. A plastic paver walk way is nicer than a muddy path littered with plastic refuse.
      - arcticbull 6y ago
        I didn't suggest this was a ploy, I'm confident that the person in question has only the best intentions. I don't think it's unfair to step back and ask what the right approach is, intentions aren't always enough. For instance, the issue with flammability/melting and also microplastics contamination is real and worth asking. I wonder if using these bricks as building foundations or something might not be a good way of solving both problems at once. However, that's an idea that would only arise if we ask pressing questions in the first place.
        cptskippy 6y ago
        It's not the ideal building material and it's a plentiful resource that would otherwise end up ideally in a landfill but likely along the side of the road. From their perspective it is a good use of something that might otherwise be litter.
- notjtrig 6y ago
  'The best solution to pollution is dilution'
- imtringued 6y ago
  Why do you advocate for CO2 pollution? Capturing that CO2 suffers from the exact same problem. You either pump it into sealed caverns and hope they don't leak or somehow extract the carbon and turn it into a solid. In the end you are "landfilling" the CO2 instead. Why not skip the middle man and just bury it directly?
robotnikman 6y ago
The microplastics which we don't see always comes to my mind when I see plastic reused in ways such as this. Though it probably does depend on the type of plastic, but I'm no chemist.
- lmilcin 6y ago
  This is plastic that would go to landfill. Expect it to contain just about everything. I don't expect this to be heavily processed. More like melted together with some additions.
- Puts 6y ago
  Microplastics is a huge problem, BUT I can't imagine this being worse than things like tiers and shoe soles.
kaycebasques 6y ago
> if you just compress the plastic into a block and lay it down to make a path then as it deteriorates surly you are just contaminating your environment with mico-plastic particles The article says that the plastic is mixed with sand, heated, and then compressed into bricks. Given this, is your comment still valid? Honest question, I'm not a material science person.
- dogma1138 6y ago
  Yes, the plastic in this case acts as a binder, in fact it would potentially be worse since the heating likely evaporated or decomposed most of the plasticizer which would make the plastic more brittle and more likely to wear off into micro plastics.
- cptskippy 6y ago
  Someone mentioned that the pavers are made from plastic bottles that already deteriorate and shed microplastics into the environment. At least in dense brick form the surface area is dramatically reduced and the deterioration rate slowed.
djrogers 6y ago
The alternative is to throw all of this plastic into a landfill where it will… leach into the soil and contaminate the environment with plastic particles. At least this option stabilizes the plastic for a period of time.
- jay_kyburz 6y ago
  I would have thought dumping the plastic in a deep pit, perhaps with some kind of solid lining would slow/prevent the plastics breaking down into "micro particles" (whatever they are) and ending up in our food.
- Nasrudith 6y ago
  Ironically most proper landfills (at least in the first world) use plastic liners along with clay as part of their barriers to prevent water contamination from other trash. I am no expert - so I cannot say if the barriers put plastic in the groundwater but that method prevents more acute toxins like dioxins and oil from getting in.

kaycebasques 6y ago

> Just because the brick is able to withstand throwing it on the rocks doesn't mean it is not going to deform under load. The end of the article says they founded in 2017 and have recycled 20 tons of waste. Maybe structural issues will emerge after 5+ years of use but it sounds like this approach has already had a fair amount of real-world usage.

dmurray 6y ago
20 tons - enough to build what, 1-10 houses over 3 years? - doesn't sound like it's been tested at scale to me.
- hn_throwaway_99 6y ago
  I'm still confused why there is so much discussion in the comments around using these bricks in buildings. The video is pretty clear about them being used as pavers.
LegitShady 6y ago
Most likely not - stuff will just fall down and nobody will talk about it. I'm sure the bricks they made in 2017 that actually see any load are already seriously deformed from creep/cold flow.

robocat 6y ago

You wouldn’t use plastic bricks for building without either serious fire risks. A non-flammable coating on the brick could potentially be developed, but not easily and perhaps not cost effectively. This is what happens when you use polyethylene as part of your building: https://www.bbc.com/news/uk-40301289 https://www.bbc.com/news/uk-40301289

labawi 6y ago
The bricks contain polyethylene, but a large part, probably most of it, is sand. Also, it is not foam in enclosed spaces, but a full hard material. A non-flammable coating would perhaps be a layer of plaster or paint? I think you are seriously overestimating the flammability of the product. Have you seen rooms with vinyl floors, PVC windows, foam / fake leather couches? Each of those will burn more easily a viciously than the bricks. My concern would be with possible structural failure at high temperatures and some fires may be able to pass through walls of these bricks. However, I don't think they are building apartment buildings from these bricks.
- robocat 6y ago
  From article: “In his report to the public inquiry, Professor Luke Bisby said evidence ‘strongly supports’ the theory that the polyethylene material in the cladding was the primary cause of the fire's spread.” and “The ACM (aluminium composite material) product on Grenfell Tower incorporates a highly combustible polyethylene polymer filler which melts, drips, and flows at elevated temperature.”. I am not a materials engineer, but it looks to me that bricks with more than 10% of polyethylene are likely to be flammable in the case of a house fire. I don’t know whether the Grenfell tower cladding had filler, but it is common for the polyethylene core to be mixed with filler within the cladding to help protect against fire, for example the ALPOLIC A2 product mentioned in [1] has an image showing a table with: ALPOLIC fr: Combustible ingredients < 30%. < 13 MJ/kg ALPOLIC A2: Combustible ingredients < 10%. < 3 MJ/kg And [1] says “Its calorific value is given as something less than 13 MJ/kg, more than four times the value considered to be of ‘limited combustibility’ in the UK”. Above facts are why I think even a large percentage of sand might still leave flammable bricks (polyethylene is like solid petroleum, until it melts and behaves more like a liquid or wax with a viscosity depending on multiple factors). [1] http://theriveroflife.com/2018/02/08/grenfell-tower-is-the-core-of-acm-panels-a-filler-material/ http://theriveroflife.com/2018/02/08/grenfell-tower-is-the-c...

lhorie 6y ago

Not a structural engineer, but I thought that the beams are the load bearers, while the bricks are more of less just filling vertical space. I think another interesting point to consider is cost. I watched a video a while back about a premise of using plastics for building roads, and in addition to the deformation/UV deterioration issues being brought up, another issue that was brought up was that concrete is cheaper than even the lowest quality recycled plastic.

londons_explore 6y ago
> the load bearers, while the bricks are more of less just filling vertical space Bricks are decorative in a few buildings, but this is by far the minority. Where bricks are used in < 8 floor high buildings, they normally are supporting the weight of the entire structure.
- dylan604 6y ago
  Where do you live that a building of modern construction is supported by bricks? In the US, multi-story residences are built on wood with a brick facade. Multi-story commercial buildings are built using wood up to 4 stories (depending on locale), and steel after that.
  - lmilcin 6y ago
    I live in Poland. Almost all buildings outside cities are bricks with bricks being load-bearing. In cities, almost all buildings older than 1950 are also made from bricks.
  - londons_explore 6y ago
    The US is the odd one out... I completely see why you'd make a temporary building out of wood so that you can build it in just a few days. But if this is a house, expected to last 150 years plus, and you're already bringing lots of bricks to the site, you really ought to be using the bricks to hold the building up and reserving the wood for the internal floors and other things that will be replaced every 75 years.

dylan604 6y ago

There are plenty of uses of bricks that do not need to support the weight of a multi-story buildings. Just because an item doesn't fit for a particular use does not mean it is not a viable solution for other things. Paving stones, mailboxes, retaining walls, etc are all examples. I for one can appreciate that someone is taking effort to resuse/recycle plastic trash into something useful like this. Maybe rather than shitting all over something for a use it's not necessarily intended for, maybe try to think of other uses this kind of innovative processing can be improved would be much more productive.

lmilcin 6y ago
Of course there are uses. I am even very happy people try to re-use what would normally be put to waste (unless it causes more plastic to disperse in environment). Just don't claim it is "stronger" than regular brick if that is not true.
silicon2401 6y ago
> Maybe rather than shitting all over something for a use it's not necessarily intended for, maybe try to think of other uses this kind of innovative processing can be improved would be much more productive. Not a very constructive response. Do you have any counterpoints to the other user's points, or do you just not allow people to point out potential issues with materials that may be used for human housing? Progress requires a balance between some people focusing on achievements and some pointing out the things that can still be improved. If I were going to rely on a new material, I'd definitely want its issues to be pointed out and addressed first, rather than just jump to using it.
- deleted 6y ago
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- kristo 6y ago
  There is a little thing called tone. And criticizing someone’s over negativity is constructive. You’d want that negativity problem to point pointed out and addressed, wouldn’t you?

gumby 6y ago

> Brick strength is measured in ability to withstand deformation under load and as far as I know there isn't any popular "plastic" that can do comparably. By definition something plastic will deform, else it wouldn't be plastic! A "rigid plastic" would be like a "miniature giant"

dogma1138 6y ago
The plasticity in their name refers to the plasticity during manufacturing which means they can be easily shaped or molded. In their usable form plastics have varying modes of failure depending on their material properties, many of them do not deform at all under stress but rather shatter just like glass.
lmilcin 6y ago
In this case the world "plastic" is used in its popular sense. Vast majority of "plastics" are plastic in physical sense. But some are not. Some undergo physical or chemical change after they are cooled and are on longer plastic in the physical sense. So maybe not "by definition".
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ineptech 6y ago

> ...this is horrible idea as the plastic is going to be broken down and dispersed in environment in large amounts This take seems trivially and obviously wrong. Recycling plastic produces a lot of nasty chemicals and is awful for the environment, but we still do it, because the alternative (chucking it in a landfill) is worse. The question is not whether these plastic bricks are bad in absolute terms, it is whether they're worse than whatever was being done with Kenya's plastic waste before this woman came along. However, it is curiously common. From elsewhere in this thread: > What about leaching [sic] chemicals into the soil and groundwater? > I do wonder about microplastics flaking off of them, though.... > ...making me concerned about plastic particulate being released... > What happens when these erode - wouldn’t plastic particles contaminate water? > ...how does this product not heavily pollute the environment? Isn't that interesting? Not to sound preachy, but did anyone have the "wait isn't this bad for the environment" reaction to any of the other stories on HN today? Starlink? That new Samsung fab plant? Shit, there's an ad on the front page right now for a gourmet dinner delivery startup. What is it about this one that brings out HN's inner environmentalist?

LockAndLol 6y ago
> What is it about this one that brings out HN's inner environmentalist? This is obvious and very easy to see, while the other examples you brought up aren't. Your examples might even be doing more damage, but because the end result is shiny, people are distracted. Plus, I'm sure there's a part of first world vs third world prejudice: "she's probably uneducated and doesn't know what she's doing, plus her accent sounds that way".
Bakary 6y ago
>Not to sound preachy, but did anyone have the "wait isn't this bad for the environment" reaction to any of the other stories on HN today? Starlink? That new Samsung fab plant? Shit, there's an ad on the front page right now for a gourmet dinner delivery startup. What is it about this one that brings out HN's inner environmentalist? This is one aspect of the tech world (and more broadly the "comfortable knowledge worker" class) that irritates me. There are so many aspects of sustainable development that are only considered from a perspective of NIMBYism mixed with orientalism. The one that bothers me the most is the portrayal of overpopulation as something caused only by people in developing countries, as if the first world wasn't part of the total count.

darth_avocado 6y ago

Fun fact: most unrecycled plastic waste (majority of plastic) from ends up in one of the two places: landfills or the oceans. It is already breaking down and leaching into the environment. I see this as an absolute win unless we stop using plastics altogether.

Clewza313 6y ago

Based on the shape and the pricing per square metre, it looks like the primary use case is for pavement. As for being a "horrible idea", this is what happens to plastic today in the slums of Nairobi: https://media.gettyimages.com/photos/kibera-slum-nairobi-picture-id184229060 https://media.gettyimages.com/photos/kibera-slum-nairobi-pic... Even if the bricks leach a bit, it's still much better than the status quo of soaking individual plastic bags in sewage for years.

tyingq 6y ago

Their website mentions "Ideally most suitable for parking areas not commonly frequented by heavy trucks" on their heaviest duty brick. So they seem to be aware. They only reference use as pavers. https://gjenge.co.ke/our-products/ https://gjenge.co.ke/our-products/

napier 6y ago

I like these kind of stories. Recycling or waste management infrastructure in many countries doesn’t cope well with plastic waste. And many countries that do a good job of collection send bales back to Asia in return trip shipping containers where much of it ultimately ends up fueling coal power stations or the fate described below. Bricks with plastic binder aren’t perfect; leachate and durability under load and abrasion are issues to be aware of. But the alternative and predominant plastic disposal method in this and similar contexts is dumping in a ditch, in a field or in an unsealed ad hoc landfill at best, or more probably burning in a heap with whatever fallen leaves and other garbage there is that’s remotely flammable. Which results in a toxic chemical smog that persistently contaminates the air, soil and water.

IanSanders 6y ago

These bricks could fill a portion of space within another substance - concrete? to reduce the amount of the latter required.

mnw21cam 6y ago

> Also, plastics tend to get soft rapidly at temperatures. I don't think plastic bricks exposed to sun (Kenya?) would fare for long. Yeah, it can get hot in parts of Kenya. But this is in Nairobi, which is somewhat elevated, and doesn't get too hot at all.

throwaway316943 6y ago

My father actually ran a plastic waste recycling business similar to this about 20 years ago. He didn’t add any filler to the plastic so it was just ground up and run through an extruded and then injected into moulds. He mostly made beams and boards. The business didn’t survive but we still have a number of the plastic boards and beams. They’ve been in continuous use on his property for the past two decades in various incarnations as fencing, shed walls, sleepers used for keeping material off the ground, etc. They haven’t degraded as far as I can tell although they might be slightly lighter in colour. Only some of the 2x6 boards deformed and broke when they were used as a fence but I think that has more to due with livestock pushing up against them. These bricks will probably work fine as foot paths, the sand and dye in them will slow UV degradation and foot traffic is unlikely to wear them much. I wouldn’t build a house out of them, offgassing would be a bigger concern for me than sagging, at least on a 1 story structure. A brick is a widely useful thing so I hope her business does well. She’s essentially just making plastic composite which is something you’re seeing in North America now used for decking.

okal 6y ago

She's a materials scientist. I'd wager that she's considered all of these factors. She's also been doing this for a while, and produced tonnes (literally) of these for, if I read correctly, a year and a half. Maybe consider that she's thought through this?

darksaints 6y ago
Of course she has. In fact she indirectly confirms that the common misconceptions regurgitated about plastic do not apply here. She takes the plastic that cannot be recycled using typical methods. The reason why some types of plastic cannot be recycled is because they cannot be melted. This is true of all thermoset plastics, and it is practically true of some thermoplastics as well (at least after they have been repurposed a couple times). The only way they could be softened enough to bind with sand is by softening them in an environment with high enough pressure and temperature, but devoid of oxygen (otherwise they'd just burn). And even if they were using melty thermoplastics, the properties will still change drastically the moment you introduce a substrate like sand or gravel and turn it into a composite. Just like how there is a massive difference between pure Portland cement (extremely brittle, with almost no load-bearing capability) and concrete, which is a composite. Nobody seems to regurgitate these rubbish misconceptions about plastic when talking about carbon fiber composites (which are held together by plastic!). I don't think I'll ever understand the techie's tendency to think they know more about certain fields than specialists that work in those fields.

tgtweak 6y ago

The plastic acts like a rebar, allowing the brick to absorb and mitigate fractures that would ordinarily crack the brick and compromise it's integrity. They would not have the same compressive strength as a cement brick, but would likely fare far better for use cases like pavers and retaining walls. I would imagine they perform better in earthquake situations and may have longer longevity than steel rebar enforced concrete.