The Great Wall of China was built with porridge in the mortar
Traversing thousands of miles across eastern Asia, the Great Wall of China has stood as a symbol of the country's military and technological know-how for more than 2,000 years. And thanks to a team of scientists at Zhejiang University, we now know that the secret to its legendary endurance is … sticky rice soup?
As explained in Accounts of Chemical Research in 2010, the scientists stumbled upon this discovery while examining mortar samples from the Great Wall and other long-standing Chinese buildings. They realized the mortar was an unusual composite created from slaked lime and congee, the former a heated type of limestone exposed to water, and the latter a pudding-like rice porridge commonly eaten throughout Asia. When combined with the lime’s calcium carbonate, a complex carbohydrate in the congee known as amylopectin helped stymie the development of calcium carbonate crystals in the mortar, resulting in a compressed structure that gave the ancient barrier the strength to withstand earthquakes and bulldozers.
While not invented until around the fifth century CE, well after the initial parts of the Great Wall were raised, the sticky rice-lime mortar was used for the well-preserved sections that remain from the Ming dynasty (the 14th through 17th centuries). Which all goes to show that along with fueling the diet of a country of 1.4 billion people, this simple porridge packs enough power to keep historic structures upright through all sorts of human- and nature-instigated onslaughts.
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