It’s just a wall. A big one. But a wall on which even Donald Trump would have been proud to have his name emblazoned.

The Great Wall of China is not one of the wonders of the world for nothing. It’s sheer scale and the effectiveness of its snaking design made it the perfect military defence bastion against the invading Mongols.

Although we still today marvel at the sheer audacity and brilliance of such a feat of engineering, more so considering the comparatively primitive tools and technology available at the time, there is one key ingredient in the basic construction material that is key to the secret of its longevity.

Rice. That’s right. Plain old simple rice. The same rice we eat today which happened to be plentiful (and therefore cheap and accessible) in China at the time.

Workers mixed lime and sticky rice to create a glutinous paste that they used as a mortar between the bricks. Researchers have recently discovered that mortar with sticky rice had smaller calcium carbonate crystals than mortar without it, creating a more compact structure and causing the crystals to stick together. Mortar with sticky rice is also less permeable to water and more resistant to the stresses of changing weather than standard mortar.

Indeed, renovations of historic masonry structures in China today still use the sticky-rice recipe.

Source: sciencedaily.com

For journal reference, see here.