I've said it before that I'm not much of a DIY-er, so I'm not likely to make my own cement blocks to build anything, but I like the idea of trying this as a project with my students to balance strength/weight/cost in a building material.
The short version of the above video is that a version of aircrete can be made with xanthan gum, rubbing alcohol, water, dish soap, and cement with some vigorous mixing (a kitchen blender, a drill with a drywall mud attachment, or a smallish cement mixer).
I'm not a 'build my own home' kind of guy, but after watching this video, I would absolutely explore the use of rammed earth as a building material if I were in the business of building my own home.
The environmental benefits seem like a slam dunk, and the striations in the finished walls are gorgeous.
I love that this is a week-long research project/workshop for high school seniors. I know that we don't do anything nearly that intensive in our material science course at Princeton - partially because of time constraints and partially because we don't have anything that would test concrete's compression strength with any accuracy.
Does anybody know of similar experiences that near you that we could recommend for our high school students?
Those are absolutely gorgeous tiles. When my wife and I were redoing our shower, I went with a raku tile for the small accent shelf that we added, but if I'd known about these cement tiles before hand, I might've been tempted by them.
Remember, of course, that these are cement tiles, not concrete tiles...ceramic not composite...though the layering might make them a laminar composite anyway...hmmm...
I ranted last week about the lack of 5-10 minute YouTube videos, so I won't rehash that grumble pile this week.
Instead I'll mention that there's an urban myth (frequently disproven) that construction workers on the Hoover Dam either fell into an couldn't get out of or were purposefully dumped into the un-set concrete used to create the dam itself.
"No, they weren't," is the short answer. The long answer has to do with the inhumanity of such a practice, the long set time of concrete, and - as this video above shows - the high density of wet concrete.
Today's video sees Dr Derek in a wetsuit trying to fill a sphere with himself and a batch of wet concrete while cutting back and forth to various explanations as to the science of concrete, the most widely used material we have and the underlying backbone of our modern world.
And at about 9:30 we get the clear explanation as to why bodies were never sunken in concrete: bodies float in concrete.
Yes, the rest of the video is well done, explaining the history of concrete - primarily around the Roman discovery, the science of concrete setting, slump testing, ingredients in different concrete batches, clunkers, the environmental effects of concrete production, cement v concrete, and much more.
It's a great, great video.
Coincidentally, I'm going to be in Helensburgh, Scotland in about a month and a week (from when this posts on 4/25/22, anyway). My wife and I are hiking the John Muir Way, a 134-mile path from west to east across the narrow 'waist' of Scotland. Maybe I'll check out the house from the video.
I find myself in an odd little focus on conservation videos of late. In the above video, Tom Scott looks at the efforts to 'dry' out a cement house from from 1902 designed by Charles Rennie Mackintosh. Mackintosh's design used Portland cement for the outside, and while it's a fascinating house, it's made from a material that is absolutely not appropriate for the damp Scottish environment.
In trying to dry out the house, they have to dry it slowly. So they have built a giant, roofed box over the house and made the walls from chainmail which keeps raindrops off the house but allows the water vapor to leave and the air and bees to come through for the 'fifteen years it'll take to dry out and repair" the house. Plus they've put in walkways and gantries that turn the house into a tourist attraction. Brilliant plan there, National Trust.
Maybe I'll extend my walk a little bit.
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| Source - https://www.news.uct.ac.za/article/-2018-10-24-world-first-bio-bricks-from-urine |
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| Source - https://www.sciencedirect.com/science/article/pii/S2213343718306043 |
The bio-bricks are created through a natural process called microbial carbonate precipitation. It’s not unlike the way seashells are formed, said Lambert’s supervisor Dr Dyllon Randall, a senior lecturer in water quality engineering.And the strength of the material is simply dependent on time and concentration of urea.
In this case, loose sand is colonised with bacteria that produce urease. An enzyme, the urease breaks down the urea in urine while producing calcium carbonate through a complex chemical reaction. This cements the sand into any shape, whether it’s a solid column, or now, for the first time, a rectangular building brick.
The strength of the bio-bricks would depend on client needs.
“If a client wanted a brick stronger than a 40% limestone brick, you would allow the bacteria to make the solid stronger by ‘growing’ it for longer,” said Randall. “The longer you allow the little bacteria to make the cement, the stronger the product is going to be. We can optimise that process.”The liquid waste from the bio-brick production, then, is further processed into a second fertilizer.
CarbonCure works with existing concrete factories to simply add CO2 without changing the concrete recipe or machines. CO2 is collected from smokestacks of large polluters like coal power or cement plants and brought to the concrete factory for recycling. Our proprietary technology injects the CO2 gas into the concrete where it is converted into more stone within the concrete......I find myself skeptical as to just how we get benefits without any downsides at all.
The best part is that it costs about the same and it keeps the same good looks and durability that you're used to with regular concrete.
It's green concrete without the trade-offs.
CarbonCure's system takes captured CO2 and injects it into concrete as it's being mixed. Once the concrete hardens, that carbon is sequestered forever. Even if the building is torn down, the carbon stays put. That's because it reacts with the concrete and becomes a mineral.Again with the extraordinary claims. I'm going to need a little more detail.
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"The best thing about it is the mineral itself improves the compressive strength of the concrete," Christie Gamble, the director of sustainability at CarbonCure, told CNNMoney."
The technology may be used to increase the compressive strength performance of a concrete mix. The strength improvement can then be leveraged in the optimization of the mix design for a specific end goal[.] (source)I hope that this technology is as perfect as is suggested, but I'm not holding my breath.
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Once injected into the wet concrete mix, the CO2 reacts with calcium ions from cement to form a nano-sized calcium carbonate mineral that becomes permanently embedded in the concrete. (source)
Previous work had revealed lime particles within the cores that surprisingly contained the mineral aluminous tobermorite – a rare substance that is hard to make.And it looks like the Romans knew what they were doing.
The mineral, said Jackson, formed early in the history of the concrete, as the lime, seawater and volcanic ash of the mortar reacted together in a way that generated heat.
But now Jackson and the team have made another discovery. “I went back to the concrete and found abundant tobermorite growing through the fabric of the concrete, often in association with phillipsite [another mineral],” she said.
She said this revealed another process that was also at play. Over time, seawater that seeped through the concrete dissolved the volcanic crystals and glasses, with aluminous tobermorite and phillipsite crystallising in their place.
These minerals, say the authors, helped to reinforce the concrete, preventing cracks from growing, with structures becoming stronger over time as the minerals grew.
As the authors note, the Romans were aware of the virtues of their concrete, with Pliny the Elder waxing lyrical in his Natural History that it is “impregnable to the waves and every day stronger”.If you want to read more, check out the original research article...or the Guardian article that's way more readable and that I quoted up above.
Our civilization is literally built on sand. People have used it for construction since at least the time of the ancient Egyptians. In the 15th century, an Italian artisan figured out how to turn sand into transparent glass, which made possible the microscopes, telescopes, and other technologies that helped drive the Renaissance’s scientific revolution (also, affordable windows). Sand of various kinds is an essential ingredient in detergents, cosmetics, toothpaste, solar panels, silicon chips, and especially buildings; every concrete structure is basically tons of sand and gravel glued together with cement.Our appetite for expansion, for building, for creation is nigh on bottomless.
