The current policy of EU countries promotes greater involvement in waste management and the search for alternative ways to utilize waste. One such waste, currently unsuitable for further processing, is the sludge generated from the recycling process of PET bottles. Based on the conducted literature review, the potential for using this waste in the production of clay-based aggregates was identified. As part of this work, four series of aggregates were produced based on post-coal clay with the addition of PET sludge (5%, 10%, 15%, and 20%). The resulting waste aggregate using PET sludge (WAPS) was then analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Furthermore, the reference aggregate was subjected to granulometric curve analysis to determine its particle size distribution. The results of this analysis allowed for the verification of the effectiveness of the aggregate formation method and the determination of the percentage content of aggregates with a specific diameter. The results of the conducted research indicate the potential use of waste aggregate using PET sludge (WAPS) in concrete technology. In future research, it is planned to conduct research on self-compacting concrete mixtures using WAPS.