Question: what are the materials used to build burj khalifa?
Answer: Burj Khalifa's construction will have used 330,000 m3 (431,600 cu yd) of concrete and 39,000 tonnes (43,000 ST; 38,000 LT) of steel rebar, and construction will have taken 22 million man-hours. The exterior cladding of Burj Khalifa began in May 2007 and was completed in September 2009.