Utilization of recycled concrete powder in sustainable cement production: A critical review

Ordinary Portland cement (OPC) production is a major contributor to global CO₂ emissions, accounting for 5-8% of anthropogenic releases. The clinker phase of cement production is responsible for a significant portion of CO₂ emissions. As the demand for cement continues to rise, the construction industry urgently needs sustainable alternatives that reduce clinker dependency while maintaining performance. Recycled concrete powder (RCP), fine particles less than 150 μm generated during recycled aggregate processing. It shows the potential to be utilized as a supplementary cementitious material (SCM), primarily due to its physical properties such as particle size and filler effects rather than its hydraulic reactivity. This paper critically reviews the engineering aspects and benefits of utilizing RCP in sustainable cement production by synthesizing fragmented evidence from existing literature. It integrates current knowledge on the physical, chemical, and mineralogical characteristics of RCP and examines their effects on workability, hydration behavior, and mechanical performance, thereby addressing a critical gap in previous studies. This review highlights that while RCP can improve mechanical performance at lower replacement levels (5-20%), it tends to reduce the compressive strength at higher replacement levels (>30%) due to clinker dilution and limited pozzolanic reactivity. Furthermore, its performance is highly condition-dependent, influenced by factors such as fineness, water demand, admixtures, curing conditions, and activation methods. In addition, the paper also critically evaluates the environmental benefits of incorporating up to 20% RCP replacement, which can lead to CO₂ reduction of up to 17.5%, alongside lower energy demand and landfill disposal. However, challenges regarding standardization, variability of source materials, and large-scale implementation hinder the widespread adoption of RCP. Future research should prioritize developing performance-based standards, conduct life cycle assessments, and optimize mix designs to enhance the industrial scalability of RCP in low-carbon construction.