After crushing building waste into pieces, the pieces can be treated and turned into an aggregate component for casting concrete. In this way, L-shaped concrete units can be prefabricated, and this works as a sustainable method of making public seats. Due to the 60-millimetre difference of its two sides, the structure is well proportioned. Also, the proper connection of both sides displays a sense of rhythm. Moreover, by positioning holes at equidistance (180 millimetres) on the structure, it can be joined as a whole by using long screw bolts. The L-shape structure allows the seat arrangement to be modified and reformed to produce various combinations that can adapt to different spatial specifications and satisfy different usage demands. Finally, based on the series of modification and reformation, such concrete public seats become much easier to integrate into modern styles of construction.