Reinforced concrete is a building material often used in dams, bridges and various buildings. Since 90 percent of the residential buildings in Taiwan are made with reinforced concrete, the use of poor quality materials can pose a great threat to life and property.
In view of this, the Bureau of Standards, Metrology and Inspection (BSMI) has revised CNS 560 'Steel deformed and plain bars for concrete reinforcement' and CNS 1240 'Concrete aggregates' to encourages the use of high quality building materials and to improve structural safety of buildings.
BSMI Director-General Liou Ming-Jong said that building structure safety is an important issue in Taiwan because the island is situated in an earthquake belt. In the event of an earthquake, the tensile strength of steel deformed bars can offer resistance, dissipate energy released by the earthquake and avoid building collapse. Aggregate materials, in complement to the bars, make the concrete stronger and more durable.
The Director-General noted that shock sensitive heat-tempered steel (which is not uniform in consistency: hard on the outside but soft on the inside) has been excluded from the revised CNS 560. Moreover, manufacturers cannot apply heat treatment to steel bars in production and all products must have country code labels on them.
According to CNS 1240, the maximum limit of water soluble chloride (main cause of sea-sand houses) in fine aggregate has been revised downward from 0.024% to 0.012%. An additional limit is imposed on the amount of shells (one of the components of sea sand) used in aggregates.
Furthermore, CNS 15706 'Method of test for shell content in fine aggregates' measures the amount of shells in aggregates. The use of poor quality shell or toxic substances can have a negative impact on the strength of the concrete aggregate.
The Director-General said that concrete aggregate manufacturers should pay attention to product safety and monitor all materials added to aggregates. Consumers are advised to purchase reinforced concrete steel bars that adhere to national standards. Such products have a
mark and certification code on them. Please visit the CNS website at www.cnsonline.com.tw for more information.
Agency in charge: Standards Division (1st Division)
Contact person: Mr. Kuo-Lung Wu
Telephone: (02)3343-5111