What’s holding up China’s oldest buildings?

Scientists, reporting in an issue of *Accounts of Chemical Research*, have discovered the secret organic ingredient added to building mortar in China to create super strong walls that withstood even earthquakes: sticky rice.

In creating what amounts to the first organic-inorganic composite material, construction workers circa 1500 years ago utilized a unique feature of a polysaccharide chain from the sticky rice. This substance, amylopectin, is a complex carbohydrate which reduces the size of calcium carbonate crystals – CaCO3 from the lime – which in turn leads to smaller, more compact internal microstructures and therefore stronger mortar.

Besides discovering the secret compound responsible for these old buildings’ supreme strength, the researchers also tested newly manufactured sticky rice mortar against modern lime mortar, and found it had greater stability, mechanical strength, and was more compatible with the older buildings. Looks like the next restoration will have to proceed after the next pot of rice is done.

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  1. Valerie Niederhoffer - June 18, 2010

    This is great news. I am going to tell all of my construction savy friends about this. I live in Buffalo-a very blue collar town.

  2. Steven V. - June 18, 2010

    I wonder…how about brown rice? Would the mortar be even stronger by being healthier?

  3. Meagen - June 19, 2010

    Extremely interesting prospect, both scientifically & socially.
    Would using rice as building material on a large scale pose any of the same problems as using corn for biofuels, i.e. an increase in the price of food due to smaller supply for human consumption? Or would large scale production involve synthetic production of amylopectin with non-rice raw material?

  4. gatcheson - June 20, 2010

    I doubt that is an issue – the rice sounds like a catalyzing agent that modifies the mortar rather than replacing it. So a little rice makes the mortar stronger but a lot of rice would just be too much.