Converting Sand into "Concrete"

..."According to recent research, a mild electric current can transform beach sand into a solid substance by triggering a process called "mineralization," where dissolved minerals in seawater precipitate between sand grains, essentially acting like a natural cement, effectively hardening the sand into a rock-like material that can resist erosion; this method is being explored as a potential solution to combat coastal erosion. "...

..."Calculations estimate that the cost of electrically cementing one cubic meter of ground ranges from $3 to $6."

Updated: Aug 22, 2024 04:02 AM EST

..."Seawater is naturally rich in a variety of ions and dissolved minerals. Therefore, a moderate electrical current (2 to 3 volts) can cause chemical reactions in seawater. The electricity has the capacity to transform some of its ingredients into solid calcium carbonate, the same material used to make mollusk shells.

With a higher voltage of 4 volts, these constituents can be turned into magnesium hydroxide and hydromagnesite — a common mineral found in various stones."...

https://interestingengineering.com/energy/electric-current-turns-sand-into-rock

Concrete is at least twice the hardness of any of these minerals formed...the formula could be tweaked maybe to produce a harder substance, maybe some additives...possibly portland cement...

..."CO2 emissions: Replacing 2% of cement with calcium carbonate can reduce CO2 emissions from cement plants by 69%."....

Maybe add in some natural fibers for toughness....

..."The Abacá banana plant – also referred to as Musa Textilis – is native to the Philippines and considered to be the strongest natural fiber on the planet. Over centuries it’s been used for shipping ropes due to its robustness and resistance to salt water, but Hannes and his team at Bananatex are the first people to make a yarn using it. Alongside its incredible strength, the Abacá plant grows in the wild without any need for additional fertilizers or chemicals and its cultivation can have tremendous benefits for biodiversity. Since its launch in 2018, Bananatex has collaborated with major fashion players such as Stella McCartney, H&M and Cos, and scooped numerous design and sustainability awards. At this year’s Biofabricate in Paris, we displayed a one off Dior jacket made from the material in our Parley booth.

For the first interview in our Material Revolution series, we spoke to the Bananatex founder about his company’s work, what fashion’s role in averting the climate crisis is, and the magic of the Abacá banana plant."...

https://parley.tv/journal/material-revolution-bananatex

...or maybe bamboo fibers....or possibly hemp fibers...but these are biodegradable...so

https://www.researchgate.net/figure/Macroscopic-photograph-of-alkali-treated-bamboo-fibers_fig1_323119360

Fiberglass might be the best bet ...

https://concretecountertopinstitute.com/free-training/complete-guide-to-gfrc-glass-fiber-reinforced-concrete/#:~:text=Use%20alkali%2Dresistant%20glass%20fibers,the%20structural%20integrity%20of%20GFRC.

So CaCO3 is heated to give CaO which is mixed with water to form CaOH which then absorbs CO2 to return to CaCO3, isn't this a closed cycle?

We have CaCO3 to begin with so what you are suggesting that all the CaCO3 not be converted to CaO or do we add it as ground up as an addition with the fly ash, which by the way will cease to be available when all the coal fired power stations are phased out..

My eyes just glaze over when a current of 2-3V is mentioned, that it is pop-science or pop-engineering. Interesting topic though.

I'm sure there needs to be some type of binding agent.

It may be similar to what the romans used.

But to get back to your question, UW-Madison had did a lot of research on the longevity on concrete, Started out as a 50 year study, but so many test coupons were made that it was extended to a 100 year study which ended in 2023. They may have something on their web site. You may have to 'poke around' on the website.

Yeah maybe some lime....

Roman concrete, also known as opus caementicium, was a hydraulic-setting cement used in ancient Rome to build structures like the Pantheon Dome and Mediterranean harbors:

• Ingredients Roman concrete was made by mixing a hydraulic-setting cement with an aggregate, typically chunks of rock. The cement was made by:
• Heating limestone to produce quicklime, or calcium oxide
• Adding water to create calcium hydroxide, or slaked lime
• Combining the slaked lime with a bulky material, often volcanic ash, to provide aluminum and silicon

• Chemical reaction When seawater came into contact with Roman concrete, a chemical reaction occurred between the lime, volcanic ash, and saltwater. This reaction created a rare crystal called Tobermorite, which made the concrete exceptionally strong.

• Durability Roman concrete's durability is due to its unique mixture of ingredients. For example, Portland cement, the most common modern concrete blend, doesn't bind as well as Roman concrete and wears quickly in seawater.

• Self-healing properties Roman concrete also has unique self-healing properties due to a calcium-rich lime clast.

I heard that Roman concrete also sets up in water…

Speaking of cooling, the Hoover Dam cooling is a pretty good read.

Read recently that whereas today we may use slaked lime for cement mortar, the roman technique for their concrete was to use the quicklime, as is , in the mixture and then add the (sea) water.

In case you hadn't heard, a worldwide shortage of sand has been developing, at least for some kinds of sand.

Sounds like the method is related to "electrocrete" - the use of small currents at low voltages to accumulate insoluble salts on a suitable support like steel mesh. See Lampe, David "Why not Grow a Building Underwater?" Next, March-April 1980