According to the UK digital magazine Dezeen, Chinese contractors tried to cut costs in Shenzen, and that cost shaving has put 15 or so buildings, including the tallest building in China, in danger of collapse.
According to the article, Contractors used sea sand, instead of river or lake sand, to make the concrete used in those buildings. The salts and chlorides found in the sea sand will corrode the rebar in the building, which could cause it to collapse. The corrosive sea sand is half the price of the less corrosive lake and river sand, which is in very short supply due to the high volume of construction in the country.
One of the 15 buildings found to have used this sand in construction is the Ping’an Finance Center designed by Kohn Patterson and Fox to be the tallest structure in China when it is completed in 2015. The building has been under construction since 2009, but work has been suspended pending the outcome of the investigations. Read more » about First Chinese Drywall, Now Concrete