I work in HKG
and no one can tell me why using concrete bricks for the apron. My guess is that it is for the ease of maintenance as Brenintw has pointed out, and also for the flexibility to add stuffs like pipes and cables running under the apron.
Here is a pic showing when the A380 visit HKG
last saturday, they actually had to run extra power supply to the aircraft. The temporay power supply is the little tower underneath the airbridge, conned off, then run two yellow cables to the nose gear, along with the existing orange ones from the airbridge. The temp power supply tower was put there in one night, I guess the apron being built with concrete bricks helped.