Michael Goodman/ENR Concrete pumps must reach 550 m. Speculation among supertall-building pundits once had the $1.1-billion Burj Dubai rising 800 meters or more. Currently, the developer admits to only 700-plus. The tower’s architect-engineer is sworn to say only 600-m-plus. And the main contractor claims not to know the final height. The secret gets harder to keep as the tower, now at about 80 stories, rises toward its pinnacle, at an average of one floor every three days. Whatever its final stopping point, Burj Dubai is on course to supersede the world record holder, the 509-m-tall Taipei 101, by summer, says