This paper presents the outcomes of an experimental study that examines the impact of substituting ordinary Portland cement (OPC) with construction and demolition waste (CDW) as an additional cementitious material. The effect of CDW on the strength of cement paste was examined with varying replacement percentages of 0, 5, 10, 15, and 20%. The study’s findings suggest that substituting 20% of OPC with construction and CDW led to a maximum reduction of 11% in the 28-day compressive strength of the cement paste. However, the compressive strength after 3 days showed a significant rise of 25.3%. The findings show that concrete with CDW exhibited greater stability in the initial stages when compared to conventional concrete. This study offers valuable insights into the potential of using CDW in concrete production. It demonstrates the capacity to maintain sufficient compressive strengths at an early stage. These results further support the use of waste in concrete applications and provide additional knowledge on sustainable construction methods.