Materials

Fracture-resistant cement inspired by the spines of sea urchins

A close examination of the structure of sea urchin spines inspired researchers to find a way to create a new, more flexible type of cement
A close examination of the structure of sea urchin spines inspired researchers to find a way to create a new, more flexible type of cement
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This is a micro-manipulator bending a cement microbar
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This is a micro-manipulator bending a cement microbar
Bending experiment on elastic cement in a scanning electron microscope, enlarged 2,000 times
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Bending experiment on elastic cement in a scanning electron microscope, enlarged 2,000 times
A close examination of the structure of sea urchin spines inspired researchers to find a way to create a new, more flexible type of cement
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A close examination of the structure of sea urchin spines inspired researchers to find a way to create a new, more flexible type of cement

The natural world is a constant source of inspiration for scientists and engineers. The latest biologically influenced innovation comes from a team of German researchers who developed a new type of stronger cement inspired by nanostructures found in sea urchin spines.

The team was inspired by the structural resilience of sea urchin spines, which are primarily made up of a brittle material called calcite. Yet despite the nature of calcite, the spines are incredibly durable because of a nano-level, brick-and-mortar style architecture.

It was discovered that sea urchin spines are so tough because the crystalline blocks of calcite are surrounded by softer areas of a material called calcium carbonate. This means that when the calcite cracks, the energy moves to the softer layer preventing any further cracking.

This is a micro-manipulator bending a cement microbar
This is a micro-manipulator bending a cement microbar

The challenge when translating this principle to cement was that cement is a much more disordered structure. Helmut Cölfen, head of the research team, says the team had to find a way to generate "fracture-resistance at the nano-level."

The key was discovering a material that only adhered to the cement particles allowing for this brick-and-mortar effect to be replicated within the cement on a nano-scale. Ten negatively charged peptide combinations were identified as perfect molecules to create the nanostructured cement.

Bending experiment on elastic cement in a scanning electron microscope, enlarged 2,000 times
Bending experiment on elastic cement in a scanning electron microscope, enlarged 2,000 times

Using an electron microscope to analyze and test the resulting optimized cement the team calculated it to have a fracture resistance value of 200 megapascals, which is approaching the value of steel.

The study concludes that this new cement could create concrete that is between 40 and 100 times stronger than current mixes.

"Our cement, which is significantly more fracture-resistant than anything that has been developed thus far, provides us with completely new construction possibilities", says Cölfen.

The results were published in the journal Materials Science.

Source: University of Konstanz via Eurekalert

8 comments
MartinVoelker
More durable concrete will help on many levels but what is the anticipated energy use in its production? Cement currently accounts for around 5-7% of global CO2 emissions, a big part of which is the 1,450 degrees Celsius to which limestone and clay mix is transformed into today's Portland cement. There is also ongoing research into replicating the types of cement used in antiquity which endure to this day, even submerged. This Roman cement is calcinated from volcanic ash, fresh water, and lime at much lower temperature, requiring less energy.
DavidA
I think that you mean that it will make for stronger (or fracture proof) CONCRETE. Cement is the powder from which you make concrete
Jose Gros
This type of improved structure concrete may be suitable for 'Space Shuttle building', see 'Space Stack Exchange' discussion.
Don Duncan
40-100 is a broad range. Why the difference? Does this make a space elevator possible? Is it stable at -100F?
Edward Vix
MartinV, Roman hydraulic concrete was a marvel for sure, but even today no one is entirely certain of the various formulas for its composition other than the general ingredients you mention. Quicklime as you note is made by burning limestone in a kiln, but it seems to me that the amount of energy required to accomplish that hasn't changed from Roman times.
Saigvre
Wotta gift NewAtlas, it turns out to be OpenAccess with a couple of stress-test movies and a supplement full of Gfx. http://advances.sciencemag.org/content/3/11/e1701216.full (and see the Supplementary Material link.) Everyone else who hasn't been surfing and therefore is saying [glasses nudge] "they don't have spines" is reminded that the spiky calcerous things that it grows spiky with (and can come off inches into your feet) are called that. Environmentalists can cheer that the idea is to not need steel in the concrete, as it bends as much as 'nacre' which is to say a 'fingernail grown rather thick.' How can they not have included tube feet though? https://askabiologist.asu.edu/tube-feet Ask for them in your as-built!
aki009
@MartinVoelker, I hope that in 20 years when the tenuous causal connection between "climate change" and CO2 has been thoroughly debunked, you will look back at your comments and consider how myopic they were. Unfortunately it will then be too late to stop the regressive taxation that hits hardest those who can afford it the least. But I will agree that it's an ingenious way to fatten the coffers of governments that are near bankrupt from decades of funky policy making. As to your concern about cement, am I to assume you would like us to start investigating mud housing instead? On a more serious note, massively stronger concrete would enable a reduction (or elimination) of rebar, and significantly thinner structural elements. In the former case valuable steel would be saved, and in the latter less concrete would be used. Both of these would be net positive no matter how you like to peel your onion.
Nik
{MartinVoelker- 5-7% of 0.04% of CO2 is totally insignificant.} However, anything that improves the efficient use of materials cant be bad, and if it allows more scope for design innovation, thats better still.