Optimizing landfilled construction and demolition waste fractions for concrete: Recycling, design, and cost analysis

During the recycling of construction and demolition waste (CDW), a significant proportion of fine particles, representing 20–50% of the processed mass, is typically disposed of in landfills due to inadequate regulatory frameworks and limited market uptake. However, previous studies have mainly focused on coarse recycled aggregates or compositionally uniform fines, leaving the practical utilization of mixed CDW fine fractions (FFs) insufficiently understood. This knowledge gap highlights the need for efficient recycling and processing strategies supported by economic assessment to enable their reliable use in construction materials. This study investigates sustainable recycling strategies for economically viable concrete production using CDW FFs derived from mixed residential and commercial demolition waste, primarily composed of crushed concrete, mortar, and masonry residues after mechanical crushing and screening. Key factors such as particle size, organic content, moisture condition, processing methods, and mix design are analyzed for their influence on mechanical performance and economic feasibility. Results show that reducing particle size improves compressive strength, while moisture content significantly affects hydration behaviour and durability performance. The optimized mixes are proposed for use in decorative pathways, lightweight blocks and non-structural concrete applications, including paving blocks. Life Cycle Cost Analysis (LCCA) indicates that cost performance depends strongly on CDW composition and screening efficiency, with equipment ownership proving more economical than rental under variable waste compositions. The findings provide practical validation for the utilization of mixed CDW FFs and contribute to understanding the relationship between processing conditions, material characteristics, and performance in recycled concrete systems.