An interesting secret of the Great Wall of China

I'm surprised (and amused) to find that a novel construction technique, used to build at least some parts of the Great Wall of China, has been rediscovered. The Daily Mail reports:

The delicious 'sticky rice' that is a modern mainstay in Asian dishes was the secret behind an ancient Chinese super-strong mortar.

Researchers also concluded that the mortar - a paste used to bind and fill gaps between bricks, stone blocks and other construction materials - remains the best available material for restoring ancient buildings.

Doctor Bingjian Zhang and colleagues found that construction workers in ancient China developed sticky rice mortar about 1,500 years ago by mixing sticky rice soup with the standard mortar ingredient.

That ingredient is slaked lime, limestone that has been calcined, or heated to a high temperature, and then exposed to water.

Sticky rice mortar probably was the world's first composite mortar, made with both organic and inorganic materials. The mortar was stronger and more resistant to water than pure lime mortar, and what Dr Zhang termed one of the greatest technological innovations of the time.

Part of the Great Wall of China (image courtesy of Wikipedia)

Builders used the material to construct important buildings like tombs, pagodas, and city walls, some of which still exist today. Some of the structures were even strong enough to shrug off the effects of modern bulldozers and powerful earthquakes.

. . .

To determine whether sticky rice can aid in building repair, the scientists prepared lime mortars with varying amounts of sticky rice and tested their performance compared to traditional lime mortar.

Dr Zhang said: 'The test results of the modelling mortars shows that sticky rice-lime mortar has more stable physical properties, has greater mechanical strength, and is more compatible, which make it a suitable restoration mortar for ancient masonry.'

There's more at the link.

It may be whimsical of me, but I find it refreshing that in an age where chemists, physicists and other scientists can whomp up the most complex and amazing chemical compounds in their laboratories, plain old-fashioned 'sticky rice' can still outdo them all when it comes to building and restoring something like fortifications. Now, if we can just figure out how to make eating 'sticky rice' repair old human bodies, that'll come in really useful for me in a few years time!



Peter