Instant stone (just add water) (2018)
rootsofprogress.org
rootsofprogress.org
Concrete made from portland cement is waterproof but it isn't moisture proof, nor airtight. It breathes just enough that the oxidation of steel isn't completely stopped. And when the rebar rusts it expands, which causes the concrete to crack, letting more moisture and air in, causting the rebar to rust faster.
There are solutions to this problem, such as using rebars made from materials less susceptible to rust (stainless steel or even carbon fiber), but for the most part they are either a lot more expensive or nowhere nearly as strong. And there is susprisingly little research into this considering how important it seems... our civilization isn't very good at committing resources to things that have payoffs longer than 50 years, so everyone continues to use plain old steel as rebar in their constructions. Meanwhile, the Roman pantheon remains standing, perhaps another couple of thousand years?
I get the impression that the continued use of steel rebar is less because there aren't superior technical solutions, but because there are significant regulatory, training and qualification hurdles. Use of non-steel rebars seems to complicate projects, and is only justifiable in special situations. Steel is usually adequate when appropriate anti-corrosion measures are taken (such as coating the rebar in epoxy).
Actually epoxy coated rebar has pretty major debonding issues in practice. If the epoxy coating was continuous then sure, but realistically during bending, cutting, tying, etc you're basically guaranteed to introduce scratches through that thin epoxy layer and once that steel starts rusting it'll tend to spread under the surface causing more cracks in the epoxy and allowing more corrosion.
The abstract of this report shows that epoxy coated rebar performs rather poorly. http://www.virginiadot.org/vtrc/main/online_reports/pdf/00-r...
>Adhesion loss of the epoxy coating to the steel surface was detected in all but one deck that was 4 years old and older. The epoxy coatings were debonding from the reinforcing bars. Whereas a bonded coating can be expected to protect the steel, a debonded coating allows chlorides, moisture, and oxygen to reach the steel and initiate a rapid corrosion mechanism. Reinforcing bars in various stages of adhesion loss showed visible signs of a corrosion process underneath the coating, suggesting that ECR will provide little or no additional service life for concrete bridge decks in comparison to bare steel. Other systems that will provide longer protection against chloride-induced corrosion of the reinforcing steel with a higher degree of reliability should be considered.
(I don't 100% buy this myself, just challenging the premise)
pro-lasting: there are plenty of places with buildings that are hundreds of years old that are perfectly fine and useful buildings and there's no really compelling reason to tear them down and rebuild them.
Another argument is that the longer stuff lasts the less you may need to maintain it. Given that maintenance costs are hard to figure out and it's hard to get dedicated budget to keep things going (the present problem in the U.S. w/r to infrastructure for example), it's unlikely that things will be well maintained throughout their potentially useful life. If the stuff just lasts better, it's more likely to have a longer useful life...which is simply cheaper.
pro-replacing: An awful lot of national GDP in many countries comes from construction projects. Keeping a constant turnover in infrastructure and housing keeps huge populations employed with decent paying jobs.
Cities don't always have an infinite utility. The U.S. Rust Belt is an example of many cities that may have outlived their intended utility. This means that populations will migrate to cities with more current utility and the need to rearrange those areas to suit the change in population is important. A fixed or stagnate inner core, that could be replaced with higher density housing, is preferable than simply sprawling out elsewhere.
If we can figure that one out we could make concrete hulls for ocean going ships that would last many lifetimes.
https://www.nature.com/news/seawater-is-the-secret-to-long-l...
The specific chemistry of how the specific silicates interact with seawater and how that forms new compounds is a new discovery.
"There does seem to be one particular application in which the Romans had a formula we would like to rediscover: maritime concrete, exposed to seawater. Normally, concrete in a pier or harbor erodes over time, both due to the salts and other minerals in the seawater, and due to the abrasion of sand and silt. However, some Roman marine structures have survived for 2,000 years. Geologists studying Roman concrete have recently discovered (2017) that the particular concrete formula used in those structures has a beneficial interaction with seawater, creating new crystals within the cementing matrix that actually increase strength. DARPA just announced that “Unlocking the Secrets of Roman Concrete” is one of many topics for exploration under a research awards program."
(A major cause of failure of concrete near or in the sea is that the rebar corrodes and expands, cause the concrete to break.)
It is also why a concrete hulled boat using this stuff would not suffer hull erosion like the existing cement fleet did during world war II and afterwards.
It isn't clear to me (but I've not found a good paper on Roman "maritime" concrete either :-)) how it interacts with barnacles and other marine life.
https://en.wikipedia.org/wiki/SS_Atlantus
(and horseshoe crabs and Cape May diamonds and ...)
I don't know how well the Roman formula would hold up, but traditional concrete tends to spall badly in constant exposure to salt water. Reinforced concrete suffers from rusting of the steel rebar segments.
Under dynamic stress, I doubt you'd get lifetimes of wear. Though several decades should be reasonably viable.
Rammed earth.
It won’t crack like cement. It doesn’t require any special chemicals like cement. Doesn’t need to be shipped anywhere...
At least not... as much of it. If you built a rammed earth structure you will use a little cement actually. So everything that’s in cement, there will be a little of it in your rammed earth home.
But mostly you’ll just use readily available local-ish materials. Now for the benefits:
- Will last 1000 years
- Perfectly finished on the inside and outside with no fussy carpentry, mudding, or painting
- Thermal mass for free
- Load bearing
- Sheds water
- Breathable
- Insects won’t bother
- Basically as strong as stone
- Stunningly beautiful
- Largely free of odd vapors and perfumes
I am a fan.
There are downsides. It’s not right for every application. It is labor intensive. And it’s skilled labor bordering on artistry. But from my research, it’s the ultimate wall there is.
> Interest in rammed earth declined after World War II when the cost of modern construction materials decreased.[citation needed] Rammed earth was considered substandard, and still is opposed by many contractors, engineers, and tradesmen who are unfamiliar with earthen construction techniques.[7] The prevailing perception that such materials and techniques perform poorly in regions prone to earthquakes has prevented their use in much of the world.[citation needed] In Chile, for example, rammed earth edifices normally cannot be conventionally insured against damage or even be approved by the government.[citation needed]
Lots of missing citations, but seems reasonable. I for one had never heard of this construction technique until today.
Rammed earth will crack in a flat application just like concrete, which also will not crack as bad in a wall formation as it will in a flat foundation type application. This is due to rammed earth and concrete having excellent resistance to compression, as gravity does to a wall, but they are both weak in tension.
Sometimes rammed earth does require binders like I said before depending on locally available materials. There is fussy carpentry involved because you need to make forms for the walls within which you ram the earth.
It's not as strong as stone, unless you use the appropriate binders and you should get your finished product tested for strength before using it in a load bearing capacity.
It's still a good building material, I do agree with that, but it is not just as good as concrete and it only approaches the strength of concrete when cement is used as a binder. No readily available natural materials come close to the strength of cement bound aggregates.
Primarily, I agree that concrete is easier if you are looking for a “no brainer”, just pay someone and forget about it type project.
But if you are willing to do some more leg work to find good people and can afford to pay them, rammed earth will be a better result for most small (<10,000 sqft) “sub-urban” applications.
(Everything thinks I am joking about this but I am 100% serious)
It's interesting because I now see the same pattern is used in old italian (mercury is "mercurio" but also "argento vivo", living silver, and calcium oxide is "ossido di calcio" but also "calce viva", living lime).
As far as I understand, in hungarian ("fürge ezüst" -> "lively silver") and german ("quecksilber" -> quicksilver) the same pattern exists for mercury, though I didn't find the calcium carbonate equivalent.
I imagine there is some shared (alchemic?) tradition there, and I wonder what other "alive" things exist.
Quicklime is different—"negesintos kalkes" which means "unextinguished lime".
In German, there's also quicklebendig – meaning "lively", "very active" – compared to lebendig, which means "alive", "living". It's slowly becoming outdated, though.
https://www.etymonline.com/word/quick
Similarly: quicklime, quicksilver, and quicksand.
Vodka being "little water" being a fave.
In my hometown we also have "aguaviva" (living water) for jellyfish.
I live in an area where trees are like weeds, but the logging industry is nearly dead because "we can't cut down the trees!!!".
So, environmentalists, which will it be? Concrete or trees? We have to build with something...
Frankly you don't have as many trees around you as you think you do (and you're probably a lot more dependent on them then you realize since local forests are usually performing an important ground support function in preventing hillsides washing away in the rain).
No environmentalist is opposing sustainable plantation timber operations, and there's plenty of those going on everywhere.
For instance, nearly all of Michigan was logged. Someone driving through the state might not think so, but most of the trees here grew back after that.
Plantation grown and old growth are very different. Just because it is a forest doesn't mean it is old growth.
I have a lot of trees and the State land next to me has even more that need thinned. I've thinned out my land for better forest health, better wildlife habitat and to reduce fire danger. The State would do well to do the same, but I is very hard to log anything but private land around here.
What happened to my logs? They went to a mill and some for pulp. They weren't old growth, that was gone long ago, but new products like CLT can make use of smaller trees.
Plantations are great, but this whole county grows trees like crazy. It isn't hard to look around and find something that can be logged in a response way, but getting approval is near impossible.
Taking a reasonably dense plantation size (which we can assume is close to optimal these days) we get 620 trees per acre (https://www.forest2market.com/blog/how-many-tons-of-wood-are...).
So a single commercial logging operation is going to be able to clear cut 2 acres of dense forest every 3 months - which will then be just gone and not coming back with any type of biodiversity or wild life for at least 10 years probably longer if ever since we're not talking plantation growth here.
You don't have as many trees as you think.
All your math doesn't change the fact that there are too many* trees in my area.
*Too many does not mean endless supply.
I can’t comment on reinforced concrete, but structural steel requires protection to meet 1+ hour fire ratings.
I just looked up some picture. Is it just plywood and OSB with 2x4s? It seems so simple.
Now this doesn't mean we should clear-cut old forests, or only have short-lived commercial forests. I think we should aim to have mostly natural forests with trees of different ages, up to hundreds of years, and use selective logging instead of clear cutting.
Timber buildings can last hundreds of years. In such buildings, using timber is a great carbon sink. Interestingly, it's the glue that will deteriorate before timber does.
Complicating matters is the fly ash component of modern concrete. Fly ash can replace 50% or more of the portland cement in concrete. Fly ash is a byproduct of burning coal. So when you replace the coal plants with solar arrays, you need to create even more portland cement than you would need to if you were burning coal (and using the subsequent fly ash in your concrete.)
Wikipedia speaks to it a bit:
> Since 1974 Joseph Davidovits, a French concrete chemist, has been proposing that the pyramids and temples of Old Kingdom Egypt were built of geopolymer “concrete” poured into molds, rather than quarried blocks of limestone. We use geological evidence and engineering principles to demonstrate the flaws in this daring hypothesis. Pyramid and temple blocks show sedimentary bedding, burrows, and optical and SEM-scale properties characteristic of normal microporous limestones, and they are cut by tectonic fractures. Block dimensions and shapes are not likely to be the product of pouring into wooden molds, and some blocks show quarrying marks. It is not easy to give a geological education to a brilliant and determined chemist.
[0]: https://www.tandfonline.com/doi/abs/10.5408/0022-1368-40.1.2...
"Since 1974 Joseph Davidovits, a French concrete chemist, has been proposing that the pyramids and temples of Old Kingdom Egypt were built of geopolymer “concrete” poured into molds, rather than quarried blocks of limestone. We use geological evidence and engineering principles to demonstrate the flaws in this daring hypothesis. Pyramid and temple blocks show sedimentary bedding, burrows, and optical and SEM-scale properties characteristic of normal microporous limestones, and they are cut by tectonic fractures. Block dimensions and shapes are not likely to be the product of pouring into wooden molds, and some blocks show quarrying marks. It is not easy to give a geological education to a brilliant and determined chemist."
That is, why would one make a kiln to heat the rock? (A mere campfire won't cut it... doesn't get hot enough.) Some speculate it could have been a lightening strike on a slab of rock, investigated by an early human who discovered the resulting crumbly powder re-solidified with water. But, this seems very unlikely. Big mystery.
In the Neolithic, the humans were firing pottery, which often requires temperatures over 850°, depending on the clay body you're using. It isn't clear whether lime kilns predate the Neolithic, but if they don't, pottery kilns would have occasionally produced quicklime by accident until you figured out that you can't temper your pots with shellfish (or calcite-containing sand) if you're going to fire them over about 800°, which is not particularly difficult. (Modern earthenware is usually fired over 1000°.) That would have made the discovery of quicklime unavoidable, if it didn't happen earlier, and of course potters must spend a great deal of time investigating the properties of their materials and how they respond to firing.
In general, he doesn't provide adequate information about safety precautions. The book is like an Anarchist's Cookbook for bootstrapping—anybody who tries its recipes without further information is likely to end up dead. It should be called The Misinformation.
The thing that got me was that when I told him that there were potentially fatal errata and where to look to see if they were already known problems, he said there was no public list; I should just take the time to write up the problems without knowing whether he already knew about them or not, and there was no way for readers to find out what errors had already been reported in the version of the book they already had. I think that says more about his attitude about accuracy than any particular error in any particular version of the book.