r/science • u/mvea Professor | Medicine • Nov 03 '19

Chemistry Scientists replaced 40 percent of cement with rice husk cinder, limestone crushing waste, and silica sand, giving concrete a rubber-like quality, six to nine times more crack-resistant than regular concrete. It self-seals, replaces cement with plentiful waste products, and should be cheaper to use.

https://newatlas.com/materials/rubbery-crack-resistant-cement/
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u/Vanderdecken Nov 03 '19 edited Nov 03 '19

Worth noting that the process of burning the limestone and shale to make clinker is a bigger contributor to carbon dioxide emissions than any single country in the world except China or the US (source). The construction industry, via the creation of cement, is killing the planet. more

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u/hankhillforcongress Nov 03 '19 edited Nov 03 '19

I'd read somewhere that the making of cement creates massive amounts of CO2, but as it cures it acts as a carbon sink.

https://www.sciencedaily.com/releases/2016/11/161121130957.htm

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u/JoHeWe Nov 03 '19

Yes, but that rate is very slow. So for a building designed for 50 years, the concrete will still be co2-positive.

As a side note, buildings are a necessity, just like food and clothing. It also takes up volumes, as it should be bigger than us. Thus it is no wonder that the construction industry is a big contributor. Whatever our economic standard, buildings will always be a big contributor.

Concrete has some very qualities that make it an efficient material, like insulation, production and installation. I don't have the numbers now, but due to its efficiency it could still be a better alternative than using steel or timber for all our construction works.

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u/pbfarmr Nov 03 '19

Concrete strength vs time is basically logarithmic though - it’s generally accepted that concrete is at ~90% compressive strength after 30 days. If CO2 recapture is a function of cure time, it stands to reason that you’d have 90% recapture after 30 days, no?