Shenzhen has long been plagued by the issue of "dangerous sea sand buildings," a problem that has drawn increasing public attention due to the risks posed by excessive chloride ions in sea sand. These ions can corrode steel reinforcements in concrete, leading to structural weaknesses and even building collapses. Reports suggest that such substandard materials are still widely used in construction projects across the city, despite regulations in place since 2004.
According to Han Ningxu, an academic consultant at Guangdong Province’s Key Laboratory for Coastal Civil Engineering Durability, the presence of high levels of chloride in sea sand accelerates steel corrosion, significantly reducing the lifespan of buildings. While regulations require desalinated sea sand for construction, enforcement remains inconsistent.
Instances of illegal use of sea sand have occurred multiple times. In 2007, Jintan Garden in Fujian used sea sand illegally; in 2011, Shenzhen's Blue Sea Resort became a dangerous structure after just two decades of use. More recently, in 2012, several real estate projects in Foshan were found to be using sea sand in violation of standards.
The Ministry of Construction issued guidelines as early as 2004, emphasizing that sea sand must be desalinated before use and warning against its application in critical structures like high-rise buildings. For reinforced concrete, the chloride content must not exceed 0.06%, while prestressed concrete should avoid sea sand altogether or only use it after thorough rinsing.
Despite these rules, the use of sea sand is becoming more common due to the depletion of river sand resources. Shenzhen officials admit that sea sand is now an unavoidable reality in construction. However, the market still sees a significant portion of unqualified sand entering construction sites.
Industry insiders reveal that while some mixing stations blend unsalted sea sand with low-chloride materials to cut costs, the testing process often overlooks chloride ion levels. Routine inspections typically focus on compressive strength rather than chloride content, leaving a gap in oversight.
Surprise inspections have shown a 9.7% failure rate, while routine checks report only 3.9%. According to Liu Nanyuan from the Shenzhen Engineering Quality Inspection Center, this discrepancy occurs because surprise tests are more rigorous. Currently, chloride ion testing is not mandatory, meaning many inspections skip this crucial step.
With such loopholes, the risk of unsafe buildings continues to rise. Industry experts urge stricter monitoring of the desalination and distribution processes of sea sand to prevent further incidents and ensure the safety of future structures.
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