Articles - August, 2007

Human Bones + Nanoengineering = Green Concrete?

Greenconcrete_2 The following post may seem a little esoteric, if not absolutely dry, but don’t be intimidated.  Bear with me a second as the idea opens up towards the end of this article.  Every year, roughly 1.89 billion tons of cement (the main component of concrete) are manufactured.  Cement accounts for about 7-8% of all human-generated CO2 emissions (a main ingredient in the recipe for climate change).  Here’s what happens: cement is made by burning fossil fuels to heat a limestone and clay powder to 1500 °C.  Then, the resulting cement powder is mixed with water and gravel and the invested energy in the powder is released into chemical bonds that form calcium silicate hydrates.  Those calcium silicate hydrates bind the gravel to create concrete. 

So, the idea goes, human bone could show us how to manufacture concrete with less CO2 emissions.  Human bone achieves a similar packing density to concrete at the nanoscale, but with human bone, this packing density is achieved at body temperature with no extra release of CO2.  Stated otherwise, bone strength is achieved naturally without having to heat powder at a high temperature, and thus, without the CO2 release.  The problem is, however, the hardening of apatite minerals in the bone takes a long time.  Say, a month or more. 

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