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The world's tallest structure ? the 828 m high Burj Khalifa building in Dubai ? has set a new benchmark for engineering super-tall buildings. In particular, it significantly raised the bar for high-performance-concrete construction, with its massive reinforced-concrete core and wings extending nearly 600 m above ground level. This paper describes the how the extreme concreting challenges were overcome on the project, including successfully pumping and placing high-performance concrete to unprecedented heights as well as preventing excessive cracking and shrinkage in the hot and arid conditions. Practical advice is provided for future projects.
Keywords
concrete structures; concrete technology & manufacture; quality control
The 828 m high Burj Khalifa (formerly known as the Burj Dubai) in Dubai, United Arab Emirates opened in January 2010 as the world's tallest structure. Its Y-shaped, 586 m high reinforcedconcrete core also represented a stepchange for high-performance concrete construction (Figure 1).
The project is the latest and largest manifestation of the world's increasing appetite for super-tall buildings. According to the Council on Tall Buildings and the Urban Habitat (CTBUH, 2010), there were 82 buildings of 300 m or greater under construction in January 2010, the vast majority of which were being constructed primarily with reinforced concrete. At least four buildings of around 1000 m are currently at the detailed proposal stage and others with heights of 1400?1600 m are on drawing boards.
High-performance concrete is a crucial part of the viability of super-tall buildings, both structurally and economically. The stiffness provided by high-modulus concrete has significant benefits in terms of limiting movement, and high strength is necessary to reduce the cross-section of vertical elements. Furthermore, the pumpability and high early strength of high-performance concrete coupled with prefabrication of reinforcing cages and advances in slip- and climb-form technology mean that large, complex reinforced-concrete structures can be constructed at rates of two to three levels per week. Properly designed reinforced concrete is thus becoming far more competitive with structural steel in terms of construction speed.
For the many super-tall structures and other major infrastructure projects under construction in the Middle East, the durability of high-performance concrete also helps to ensure the required service life will be achieved in a hot, chemically aggressive environment. However, such concrete can be more sensitive than conventional...