This study investigated the utilization of waste refractory bricks (RB) as coarse aggregate in concrete production, investigating their effect on compressive strength, CO2 emissions, and ultrasonic pulse velocity (UPV). Two types of RB, alumina and magnesia, were tested at replacement levels of 0%, 15%, 30%, and 50%. The results showed that increasing the proportion of RB caused a decrease in the compressive strength of concrete, especially for magnesia-type RB. This decrease was due to several factors, including the non-uniform shape of RB particles and higher porosity. However, at lower replacement levels (15%), the incorporation of alumina-type RB still met the minimum acceptance criteria for construction applications. In addition, the use of RB significantly reduced CO2 emissions, indicating the potential for sustainability in concrete production. In addition, this study also found a strong positive correlation between UPV and concrete compressive strength. This suggests that UPV can serve as a reliable predictive tool to estimate the compressive strength of concrete. These findings provide valuable insights into the mechanical behavior of concrete containing RB and contribute to the development of acceptance criteria for the use of RB in concrete, encouraging more environmentally friendly construction practices.