Rubbery concrete is made to take hits without cracking

Authored by newatlas.com and submitted by mvea
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Buildings that are constructed with military or civil defense applications in mind need to be tough. It was with this in mind that a new form of concrete was recently developed, that is far more resistant to cracking than regular types.

Developed by scientists from the Military Studies Center at Russia's Far Eastern Federal University, the concrete doesn't simply use pure cement as a binder. Instead, approximately 40 percent of the cement is replaced with a binder made up of rice husk cinder, limestone crushing waste, and silica sand.

This substitution gives slabs of the concrete a somewhat rubber-like quality, allowing them to contract and spring back when subjected to impacts, instead of cracking. In fact, the material is reportedly six to nine times more crack-resistant than regular concrete. Additionally, it self-seals upon being poured, meaning that it could be well-suited to the construction of underground structures such as bunkers.

And as an added bonus, because the new concrete replaces cement with plentiful waste products, it should also be cheaper to use.

"It was important for us that the concrete holds up until the first crack for as long as possible, because after a concrete structure cracks its deterioration is just a matter of time," says the university's Prof. Roman Fediuk. "Today the whole world is working on counter-terrorist security facilities that would defend other structures from a shell hit or a plane crash. We've approached this issue from our own angle and developed an impact-proof material. On the next stage of our work we want to create radiation-resistant concrete."

A paper on the material was recently published in the journal Inorganic Materials: Applied Research.

Source: Far Eastern Federal University via EurekAlert

danielravennest on November 3rd, 2019 at 12:09 UTC »

For those not familiar with concrete, it typically is made from gravel, sand, cement, and water. The water turns the cement powder into interlocking crystals that bind the other ingredients together.

There are a lot of recipes for concete, but the typical "ordinary Portland Cement" concrete is made with a cement that starts with about 5 parts limestone to 1 part shale. These are burned in a high temperature kiln, which converts them chemically to a product that reacts with water.

Lots of other materials will do this too. The ancient Romans dug up rock that had been burned by a volcano near Pozzolana, Italy. The general category is thus called "Pozzolans". Coal furnace ash and blast furnace slag are also rocks that have been burned. They have long been used as partial replacements for Portland Cement. Rich husk ash and brick dust are other, less common, alternative cements.

Note: Natural coal isn't pure carbon. It has varying amounts of rock mixed in with it. That's partly because the coal seams formed that way, and partly because the mining process sometimes gets some of the surrounding bedrock by accident.

Portland Cement got its name because the concrete it makes resembled the natural stone quarried in Portland, England at the time.

kiHrt on November 3rd, 2019 at 12:05 UTC »

How is the compressive strength compared to traditional concrete mix?

geogle on November 3rd, 2019 at 11:24 UTC »

Could be very useful in poor earthquake prone environments that often underuse rebar. This may offer some of that needed tensile strength. However, it would need to be specially tested for it.