Activity quantification and assessment of recycled concrete powder based on the contributions of the dilution effect, physical effect and chemical effect

Improving the utilization of recycled concrete powder (RCP) is crucial for optimizing the resource utilization of construction and demolition waste (CDW). The assessment of RCP activity is essential for its extended applications. However, regarding RCP with complex compositions and high content of inert materials, the current standard activity index method fails to provide a comprehensive and efficient assessment. This study aimed to elucidate the activity of RCP, correlate the particle characteristics of RCP with its activity, and propose activity quantification and characterization methods applicable to RCP from different sources. Specifically, the type, particle size distribution, and replacement of supplementary cementitious materials were investigated to categorize their influence as dilution, physical and chemical effects on mortar strength. The relationship between the particle size distribution, replacement, and rehydration properties of RCP and these effects was explored. The results showed that the contributions of dilution, physical and chemical effects of the RCP to the activity could be effectively predicted by their fundamental properties, which were also verified by the Random Forest model and the empirical model for accuracy and rationality. Finally, the activity evaluation method based on the fundamental properties of RCP is proposed. The study findings present an efficient means for accessing the activity of RCP from different sources, thereby facilitating their better applications and enhancing the utilization of CDW. •The activity of RCP is categorized into dilution effect, physical effect and chemical effect by the compressive strength.•The contributions of the dilution effect, physical effect and chemical effect of RCP to the strength are quantified.•The relationship between the fundamental properties of RCP and its effects is established.•The activity evaluation method for RCP is proposed, allowing for the rapid assessment of RCP from various origins.