Low-carbon concrete stays strong with polymer lattice reinforcements | Hacker News Reader

Low-carbon concrete stays strong with polymer lattice reinforcements

newatlas.com

67 pointspanabee34 comments

Even better: carbon-cured concrete.

The process binds carbon dioxide, and it is even possible to make the final product carbon negative if ordinary cement is replaced with alternative binders with a low carbon footprint.

Carbon neutrality is achieved using blast-furnace slag and carbon negativity using a mix of slag, green liquor dregs and bark ashes.

https://www.vttresearch.com/en/news-and-ideas/turning-cons-c...

Instead of polymers you can also use elephant grass: https://marketplace.chemsec.org/Alternative/High-performing-...

That seems even more environmentally friendly. It's all being tested though. You don't want to rush things when it comes to concrete.

ABS and other plastics inside concrete doesn't sound great for the environment...

Concrete is already pretty bad for the environment - a chunk of it lasts thousands of years, with a pretty alkaline surface meaning many plants don't want to be nearby, but otherwise at least is mostly inert like rock.

By adding polymers, we're probably going to have plasticisers oozing out of these things for thousands of years, turning all the fish into all three genders at once, together with lots of as-yet-unidentified effects of polymer breakdown products.

Really what we want is concrete to absorb co2 over time. I know that's not how the chemistry works but it'd be a great way to solve the diffuse carbon problem.

Yeah that doesn’t sound great. If it effectively encapsulates waste plastics in a steady state across thousand-year timeframes then it could be a net positive, but otherwise does sound like a big liability/disaster in slowmo.

Concrete has a high compressive strength without steel rebars. Steel rebars are added to concrete to increase its tensile and sheer strength. The article alludes that these polymer reinforcements can replace steel but then only talks about increasing the concretes compressive strength, which exactly not why they're used.

The article did kind of circle around the objective of the work without digging into it. The picture and some of the text (strain test) indicates they are evaluating tensile loads, but it didn't really say if this was intended to increase mechanical performance, reduce weight, reduce concrete used, etc.

I think the point, given the title, is to reduce the volume of concrete that is cured for a given pour by replacing some of it with polymers.

Using even less material seems likely to lead to most buildings trying to do only that and failing to include any other mechanism for acoustic isolation and privacy.

I am almost equally worried about other previously assumed goals that traditional construction methods happen to fulfill but which could be overlooked due to under-specification. What things? I don't know, and my worry is that experts in those fields might not either until that data is gleaned the hard way.

Great points. Any major change in 'concrete' is likely to yield a few surprises when folks try to drop it in as a replacement for the standard.

Fibre reinforced concrete is not really "news", we were using the one or the other forms more than 30 years ago, exactly to prevent cracks, the issue in real life applications is to distribute the fibres (be them metallic or plastic).

But this, see the actual picture of the lattice on the article:

https://www.sciencedirect.com/science/article/pii/S026412752...

look more like traditional reinforced or mesh reinforced concrete.

ABS is not such a great material for construction due to its sensibility to UV rays, surely there are "better" plastics for this use even if maybe not suited to 3D printing.

Why is UV sensitivity a problem for something that's going to be embedded inside the concrete?

>Why is UV sensitivity a problem for something that's going to be embedded inside the concrete?

IF it will ever become an actual mass product, the lattice will be manufactured in "bulk" (not 3D printed on spot) and it will become a "building material" like rebar or steel mesh, etc.

Normally building materials are stored in the open for months either at the factory, at the store or on site before being actually put in the concrete formwork.

You simply don't want something that needs to be stored in a dark, cool place.

Very early versions of polyethilene pipes (think of 30+ years ago) were not UV resistant/stabilized and of course they were put in digged trenches and covered, but it came out that after a few years they started leaking, you don't want to have something structural that may loose its properties in a few years.

> The team found success using acrylonitrile butadiene styrene (ABS) polymers to produce the lattice

So, don't spill acetone on it or your building will collapse?

I realize this is just research and the final product will likely be more robust. As someone who just had a bottle of acetone leak in the freezer(home chemistry gone wrong I guess), I am acutely aware of the destructive power of simple acetone. Did I mention freezers are apparently made of ABS?

Yeah, don't use acetone or instant glue on Styrofoam (unless you want a gooey mess)

Isn't the goo also highly flammable?

As kids, my friends and I used to refer to a mix of polystyrene and gasoline as "DIY napalm".

> As kids, my friends and I used to refer to a mix of polystyrene and gasoline as "DIY napalm".

Yeah, I experimented with this once as a teenager. It's sort of fascinating how much polystyrene you can dissolve into gasoline (makes sense, as EPS is mostly air). Burns with thick black smoke and an acrid smell..

I didn't have any WP to blend into it, though. In retrospect, that was good.

It's not too different from the real thing. It's one of those "don't try this at home" things. :D

Longevity is turning out to be a major issue with steel reinforced concrete. This might solve some of that by using reinforcements that do not react chemically with the concrete. Lifetime usage issues including durability and recycling loom large in this context.

If carbon emissions become really expensive, other materials than concrete become more viable.

Steel can be quite carbon intensive as well though.

Timber and mud could become great again. Also hydro cut stone.

Engineered timber is surprisingly strong and fire resistant - the problem is in what the word "engineered" means in terms of environmental impact.

What are you referring to when you mention hydro cut stone? A quick google shows gemstone cutting, small subtractive milling of gargoyles and cutting/etching of thin decorative stone.

Are you talking about a quarrying process? I've got a little bit of knowledge about quarrying as there are many active limestone quarries in my area, but always interested to learn more.

My guess would be water-jet cut stone blocks. At the quarry you often cut stuff off in big slabs; once you’ve got the slabs at the water-jet, you could cut standard dimension blocks out of the slab and have a pretty modular building material.

Yeah that's what I meant. Why would one prefer concrete over that?

Imagine the scale of the gaping maw left behind after a century of quarrying for high quality stone to support modern city construction.

Concrete materials come from somewhere as well. But yes, if the material would cost more, it would be used more sparingly.

Maybe I come from a country that has plenty of solid rock to go around.

While not my field at all, I would imagine that given the relatively generic character of the source material required for concrete it might be easier to find suitable locations for extraction. Although I seem to recall reading about potential shortages for certain types of sand, so maybe I'm wrong about that.

Generally speaking, whenever specific qualities of a raw material become linked to its intended use, the market becomes more willing to accept negative externalities in its procurement.

Timber is about as pure stored CO₂ as you can get.

It's the impermanence of standard stick construction that ruins the gains of switching materials. Cross laminated timber seems to have potential, however it is significantly more expensive for the moment.

The formaldehyde-based adhesives that are used in engineered timbers also complicated the picture a bit, from long-term health and sustainability perspectives.

Perfect world would be a much larger supply of old-growth hardwoods with characteristics that make them ideal for construction. If some synthetic means of growing such material comes around, that could be a game changer.

My understanding is that polyurethane adhesives are better suited for CLT, and don't have the same emissions problems.

Your point is well taken though: the entire supply chain needs to be accounted for, in addition to the lifetime of the structures.

There are also ways around this. You can join softwood with screws made out of hardwood. There's a German company making those. Some companies join boards with aluminum nails. You can make massive wood from cheap material without glue. There's a company that makes boards with a wavy surface. Multiple boards lock together easily. They made a prototype bridge with very little fastening.

Steel is the easiest to recycle and reuse though.

The concrete-strengthening carbon-sequestering solution I'm interested in is adding graphene to concrete to increase compressive and tensile strength[0]. A team at Rice University has developed a simple means of producing "turbostratic" graphene from just about any carbon-containing waste[1].

0: https://onlinelibrary.wiley.com/doi/epdf/10.1002/adfm.201705...

1: https://www.nature.com/articles/s41586-020-1938-0

I wonder what the environmental impact of graphene is from an end of life waste management point of view.

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