Due to the relative differences in concrete stiffness and ground compressibility, it has been
found that the sub-face slab backing is expected to create a certain amount of space, but the case
has so far been limited. Research suggests that IE (impact echo) exploration is most appropriate
as an efficient way to investigate the cavity of the facade of the concrete structures, but further
reinforcement investigation is required as the result of a single exploration is difficult to reduce
that uncertainty. Therefore, reinforcing non-destructive investigation without high frequency wave
is necessary, and IR (impulse response) exploration and concrete non-resistance exploration are
considered appropriate.
