The recipe to make concrete is pretty simple — cement, aggregate and water — but the strength of the final batch can vary wildly depending on the kinds of aggregate and cement used and the proportions they’re mixed in. Commonly the aggregate used in many modern building projects consists of crushed gravel or other rock, including sand, and that’s the cause of so much distress in the Chinese construction industry at the moment. Inspections by state officials have found raw, unprocessed sea sand in at least 15 buildings under construction in Shenzhen, including a building which, when finished, was set to become China’s tallest.
It can take only a few decades for a building to become dangerously unsafe if untreated sea sand is used in its concrete — including the possibility of collapse. While this scandal has been confined only to Shenzhen thus far, the possibility of it spreading to other Chinese cities is cause for concern. The country currently has nine of the 20 tallest buildings in the world under construction, while there were reportedly so many skyscrapers under construction in 2011 that it worked out as a new one being topped out every five days right through into 2014.
The Ping’An Finance Center is one of several very tall skyscrapers under construction in China, but it might not have the title of the country’s tallest for too long even if construction resumes. The highly publicized plan by Broad Sustainable Building to build the world’s tallest building, Sky City One, in only 90 days in Changsha, attracted skeptical responses from engineers who felt it was completely unrealistic — the head of the company behind construction of London’s Shard even joked that he’d retire if Broad pulled off the stunt. However, he can rest easy, as the skyscraper has yet to break ground, as it continues to be delayed.