Abstract: A concrete receptacle assembly includes a frame that supports a series of cells that are used to receive waste concrete and mold the waste concrete into synthetic riprap blocks. The cells are defined by a series of angled partitions that are mounted within the frame, with the angled partitions defining the shape of the synthetic riprap blocks produced. In operation, the waste concrete is distributed into the cells, where it is allowed to cure for a predetermined period of time. Once cured, the concrete receptacle assembly is upended such that the synthetic riprap blocks will be dislodged from the cell. Once the synthetic riprap blocks have been extracted, the concrete receptacle assembly is prepped for the next cycle of production.