
Rubber concrete that self-seals and is cheaper and more environmentally friendly - atombender
https://newatlas.com/materials/rubbery-crack-resistant-cement/
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qndreoi
Rubber is a latex or elastomer, not the substance described here. The original
article used rubbery in the title, an adjective that means tough and elastic.
Better not to have been changed.

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pmoriarty
Another interesting material is Papercrete.[1]

 _" Papercrete gets its name from the fact that most formulas use a mixture of
water and cement with cellulose fiber. The fiber is usually acquired from
recycled newspaper, lottery tickets and phone books. The mixture has the
appearance and texture of oatmeal and is poured into forms and dried in the
sun, much like the process for making adobe._

 _" Dried papercrete has very low strength, but fails by slow compression (due
to the large air content and hence compressibility) rather than in a brittle
manner. Concrete and wood (though dry soft wood can be as high as R-2 per
inch, high moisture content reduces this value markedly.) are not known for
their insulating qualities; however, papercrete also provides good
insulation..._

 _" Unlike concrete or adobe, papercrete blocks are lightweight, less than a
third of the weight of a comparably-sized adobe brick. Papercrete is mold
resistant and has utility as a sound-proofing material."_

[1] -
[https://en.wikipedia.org/wiki/Papercrete](https://en.wikipedia.org/wiki/Papercrete)

~~~
atombender
Also hempcrete [1], an environmentally friendly variation on limecrete which
was successfully used in an episode of the recent series Grand Designs: The
Street [2].

[1]
[https://en.wikipedia.org/wiki/Hempcrete](https://en.wikipedia.org/wiki/Hempcrete)

[2] [https://www.granddesignsmagazine.com/grand-designs-
houses/44...](https://www.granddesignsmagazine.com/grand-designs-
houses/445-grand-designs-the-street-episode-3)

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pkaye
> rice husk cinder, limestone crushing waste, and silica sand.

Is this really a new idea? Back in the 90s when I did my civil engineering
degree (I changed major later), my professor was big into rice hull ash as an
concrete additive. He did tons of research into the properties.

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Doxin
It's probably not a new idea, but it might be newly-relevant seeing as
concrete is under the magnifying glass for its emissions as it's curing.

More expensive concrete might have become economically viable if it emits less
greenhouse gas or if you need less of it. And if it's not currently
economically viable it might still become viable in the future, prompting more
research into it by companies hoping to have first-mover advantage.

That said I'm not a concrete expert. I don't know why this sort of concrete
isn't currently being used, nor the relative pricing of it relative to
ordinary concrete.

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misterprime
If it's cheaper and more resilient, why is it only focused on civil and
military structures? What's the trade off?

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beerandt
Probably because (among other reasons) structural reinforced concrete
_depends_ on cracking, both to develop internal strength and to prevent abrupt
catastrophic failure. ACI building code (or a derivative) applies in most US
jurisdictions, and it relies on heavily on the premise of concrete showing
cracks before reaching the failure point of the internal steel. It ensures a
failure mode that illicits a warning.

(The internal strength development _probably_ wouldn't be as much of an issue
with the "rubbery" concrete, assuming the compressive strength is equivalent,
but I'm sure there are other considerations I haven't thought of. You're
changing fundamental properties of the material that is expected by most
designers. Existing brittleness is accounted for and expected.)

Civil Defense and Military applications don't necessarily have the same design
requirements, or need to be as compliant with a particular building code, as
they're typically exempt from local building regulations and/or have their own
separate building standards.

On the other hand, asphalt pavement design is based on principles that could
benefit from such a material without having to completely re-invent the design
code.

~~~
specialist
Great explanation, thank you. A cogent answer to a question I would have never
thought to ask.

Maybe that visual inspection requirement will change as we develop non-
destructive testing options.

~~~
beerandt
Non destructive testing exists and is fairly mature for reinforced concrete.
It's just more expensive. But it's not so much about testing, since once a
structure is built, you're not going to get the owner to pay for any more
testing, until signs of potential failure arise. You need an obvious reason to
test in the first place.

Testing also somewhat implies that the design or material is defective; but
that's only two paths to failure out of many. More likely, the structure is
overloaded, or supplemental supports are removed prematurely, as is what seems
to be the case for the recent hard-rock hotel collapse in New Orleans.

This isn't too say that new materials don't have a beneficial use. We would
probably need to develop a new and separate sub-discipline, the same way pre-
stressed and post-stressed concrete structures are designed, which have since
been included into ACI code.

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Zenst
How does this bond with existing concrete? Could it be used for
repairs/renovations of existing structures.

Also - reinforced concrete works as the steel rods that give the concrete
strength, expand and contract at exactly the same rate as concrete. Is that
still the same with this version?

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misterprime
>steel rods that give the concrete strength, expand and contract at exactly
the same rate as concrete.

How cool, didn't know that. Makes so much sense.

~~~
beerandt
They're close, but not exact. I think concrete on usually given as 13.5
(0.0000135 in/inR), and steel as 11 (0.0000110).

It's this difference that reduces RC life expectancy from 100's of years (as
advertised by the concrete industry in the early 1900's) to the neighborhood
of 10-50 years that we typically see.

Whereas glass and platinum, for instance, are generally considered to be
exact, and are used for precision measuring and calibration.

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jitendrac
I doubt about the mainstream sustainability of it, if considered with mega
structures.

Currently, more high-rise building are built then past. The base of building
requires high-rigidness and compressible strength which is fulfilled by
traditional concrete. But if we replace it with some flexible
substance[ideally only at higher loads], It will start bending when
traditional concrete would perform easily. moreover it will also affect all
the application which are based on rigidness of concrete, eg, Floor tile/stone
will crack open, furniture will break, your plumbing will bend etc.

so, much more research is needed. and possible whole other way of construction
process has to be created to sustain new challenges.

~~~
pas
I don't know the numbers but it doesn't sound like it makes concrete wobbly-
wiggly.

And ther are always shearing forces, especially with high-rises (wind), and
probably this added plastic helps with that. (Less creeping cracks, better
handling of repetitive stress / cyclic elastic deformation - eg bridges,
roads, floors.)

~~~
jitendrac
> it makes concrete wobbly-wiggly.

That is why i wrote "some flexible substance[ideally only at higher loads],"

yes, it can make positive impact on many use-cases. But I think we should
focus more on the production of cement with negative or neutral CO2 yield.
Cement is one of the least blamed cause of CO2 emission, but It really should
be blamed.

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notelonmusk
Interesting how we use "more environmentally friendly" now instead of "less
environmentally hostile". Language skewed towards marketability.

~~~
Nasrudith
When has "less environmentally hostile" ever been used in the first place?
Hostile itself would be the wrong term anyway - it is usually apathy not some
deranged hatred of nature that drives pollution in building materials.

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galaxyLogic
How about this idea: Mix ping-pong balls with concrete. It becomes much
lighter then. Because it is lighter it can much more easily support the weight
of the (similar) concrete structures above it. Just a thought has anyone tried
such a thing?

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marcusverus
Two issues: 1) unequal dispersion of the balls could create super weak spots
that are mostly empty space. I'm not sure how engineers could use a material
where the structural integrity isn't consistent. 2) If water ever penetrated
the swiss-cheesyness of the concrete in freezing weather, you'd be in big
trouble.

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disillusioned
Yeah, this is already a nightmare with rebar in reinforced concrete. Just
imagine actual ping pong ball sized voids filling with moisture. Swiss cheese,
indeed.

~~~
galaxyLogic
But it wouldn't be holes, it would be water-tight ping-pong balls.

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TaylorGood
What’s the dry time? And can it be expedited with an industrial “blow dryer” ?

~~~
baq
concrete doesn't dry, it cures. it's beneficial to spray curing concrete with
water.

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m3kw9
Would it flex too much where it shouldn’t?

