Part of that is because they have to other wise the building would collapse on its own.
A big issue people don't talk about is that a lot of the concrete China makes is subpar and not up to spec by US or EU standards - they don't use the right (aka more expensive) grade of sand, so the concrete doesn't bind as strongly as it should. The sand used to make concrete has to have rough edges, something about the surface area, which ironically means that desert sands aren't very useful - they've been rounded by wind erosion and rubbing against other sand grains.
A big issue people don't talk about is that a lot of the concrete China makes is subpar and not up to spec by US or EU standards - they don't use the right (aka more expensive) grade of sand, so the concrete doesn't bind as strongly as it should. The sand used to make concrete has to have rough edges, something about the surface area, which ironically means that desert sands aren't very useful - they've been rounded by wind erosion and rubbing against other sand grains.