When in Rome, build something concrete

When in Rome, build something concrete

Researchers at UC Berkeley are studying ancient Roman concrete in an effort to come up with a durable, yet green concrete. Shipping was instrumental to the expansion and sustainability of the Roman Empire. Using volcanic ash and seawater, the Romans developed concrete that has withstood the harsh marine environment for over 2,000 years. Scientist used the Advanced Light Source at Lawrence Berkeley National Laboratory (Berkeley Lab) to look at fine structures in the Roman concrete for the first time.

Roman concrete has a smaller carbon footprint because the modern cement (Portland cement) burns calcium carbonate (limestone) and clays at 1,450 deg C while lime used in Roman concrete requires only two thirds of that.

If Roman concrete is so good, why is it not still used? As the Roman Empire declined, the need for shipping and therefore the need marine concrete diminished. Also, modern concrete takes a fraction of the time to cure, compared to Roman concrete.

Edit

I should have defined what concrete is. Concrete is a composite material, made of “filler” (e.g. pebbles) and a binder (cement). So what is cement? More importantly, what is Portland cement, which is mentioned in the article and is the most common type of cement used. Portland cement is calcium silicates mixed with aluminum and iron containing clinker phases. (http://en.wikipedia.org/wiki/Portland_cement). So what are clinker phases? Clinkers are balls of sintered (baked) material made by taking a mixture of materials and heating them with very high heat. So the big difference between Roman concrete and modern concrete is really the clinker, not so much the filler. Also note that Roman concrete does not use steel reinforcing bars (rebar), so modern concrete has much higher tensile strength.

Cement Clinker on the Belt

More here:

http://newscenter.lbl.gov/news-releases/2013/06/04/roman-concrete/

Image source and reference: http://newscenter.berkeley.edu/2013/06/04/roman-concrete/

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