think again
I don't think you can build concrete that high.
Try telling that to the guys who built the Patronus Towers to 1371 feet.
or the Jin Mao Tower built to 1378 feet.
or for a little closer to home but not as tall, the Two Prudential Buildings in Chicago at 920 feet
<img src=http://www.idartatravelimages.com/images/t/TCGA-0501AA.jpg">;
there is a good article here:
http://www.cement.org/buildings/
with this excerpt:
Until recently, the world's tallest buildings were in the United States, but in 1993, the tall building construction boom shifted to Asia with the erection of the 1207 ft (368 m) Central Plaza office tower in Hong Kong.
Two major high-rises in Asia are the 1371 ft (418 m) Jin Mao Tower in Shanghai, China, and the 1378 ft (420 m), twin Petronas Towers in Kuala Lumpur, Malaysia. These monumental towers use composite structural systems, combining vertical components such as cores, columns, and shear walls of concrete that have strengths of up to 11,600 psi (80 MPa) with structural steel horizontal members to resist lateral and vertical forces.
The two tallest concrete buildings in the United States were completed in Chicago in 1989. Both the 969 ft (295 m), 311 South Wacker Building and the 920 ft (276 m), Two Prudential Plaza Buildings took advantage of 12,000 psi (83 MPa) high-strength concrete in the fabrication of cast-in-place, steel-reinforced columns and walls at the buildings' lower levels to support the total dead and live loads of the structures. The middle and upper levels of the buildings, where total accumulated forces are lower, were constructed with concrete in strengths ranging from 4000 psi (27.6 MPa) to 10,000 psi (69 MPa).
-Steve G.