First steel thinning, now corrosive concrete...
Back in September 2011 we reported on the concerning increase in steel thinning across China. Zhengzhou and Shaanxi Province were two of the regions highlighted in the piece but the rumours that manufacturers of steel reinforcement rods were stretching their materials to greater lengths to maximise profits regardless of the ramifications to the structural stability of the buildings they would be used in reached much wider.
It has now emerged that another scandal has been bubbling under the surface of the Chinese construction industry where deadlines get shorter and buildings stretch further skyward. On 19 March, Shenzhen’s Housing and Construction Bureau released an official statement which warned of the consequences of using substandard concrete and thin steel bars, suggesting that the latter is still an issue in this competitive market.
Last week media reports began to emerge that ‘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’ [Wired]; however a notice on Shenzhen’s Housing and Construction Bureau's website on 18 March stated that a document posted that day had been false in its claims that a number of residential buildings under construction in the city had been found to be using concrete made with sea sand.
The use of sea sand in the production of concrete is considered dangerous as the material contains chlorine and salt which can corrode the steel reinforcement rods within a construction project, rendering it unstable. Sand from freshwater rivers should therefore be used instead.
There are scores of case studies where construction projects which utilise this budget material have either collapsed or been rendered unsafe. These include the Fulin Homes Community in Taiwan where over 400 residents were forced to move out of their houses in 1994 due to dangerous conditions and had to have their homes rebuilt over a six-year period.
The aforementioned media reports stated that a number of construction projects in Shenzhen have been stalled after concrete containing sea sand was discovered, including the Kohn Pederson Fox-designed Ping’an Finance Center [see image] which was due to be China’s tallest tower at 660m when completed in 2018. Requests for comment by KPF were unanswered at the time of going to press.
A statement from Shenzhen’s Housing and Construction Bureau reads: “Substandard sea sand is strictly prohibited. Ready-mixed concrete producers should purchase sea sand that has gone through the desalination process and have passed quality inspection, and to implement dynamic monitoring of chlorine ion content of sands for concrete. Construction units shall give on-site tests of chlorine ion content for ready-mixed concrete when entering the construction sites and increase the detection of chlorine ion content indicators of ready-mixed concrete test sample submission.”
The Bureau has henceforth revoked the certification of the East Ocean Building Material Co. Ltd, ordered eight companies to suspend business for rectification and withdrawn the certificates for sixteen ready-mix concrete producers. Six firms have also had their business suspended for more than six months as a result of providing substandard concrete.