There are many abandoned lignite mines in the Tokai region of Japan. They are now being filled with materials because of the possibility of caving and collapsing or subsidence in urbanized areas above these abandoned mines. The filling material is initially in a slurry state and it solidifies with time after filling the cavities. The main material of slurry is by-products produced at a neighboring macadam factory. The utilization of by-products as filling materials could not be done until now due to the restrictions of some regulations. There are two purposes of this research. The first purpose is to examine the suitability of various recycling materials as filling materials all over Japan. The second purpose is to develop new cavity filling materials from recycling materials. It is experimentally confirmed that some of by-products can be successfully utilized as cavity filling materials.