Optimization of Slurry Impregnation Technique for Upcycling Carbonated Recycled Concrete Aggregates for Paving Concrete Applications

Extraction of recycled concrete aggregates (RCA) from construction and demolition waste is an effective way to induce sustainability in the highway sector. However, inclusions of these inferior materials could significantly deteriorate the performance of paving quality concrete (PQC) due to the presence of old adhered mortar (AM) around the RCA. Numerous techniques are available in the literature that primarily address the issues with AM for increasing the potential of RCA for concrete applications. However, the energy demand and associated emissions are higher in most of these techniques, whereas carbonation and slurry impregnation (SM) techniques are regarded as the best ways to economically enhance the characteristic of RCA for large-scale applications. The present study is the first of its kind to optimize the SM process for carbonated RCA for PQC roads; RCA was stockpiled in the natural environment in loose condition for around 12-14 months for fully carbonating the Portlandite phase. The parameters optimized are slurry material type (silica fume, fly ash, and cement), their concentrations (20% - 60%), exposure duration (4-12 h), and RCA sizes (20 mm and 10 mm), whereas the porosity, toughness, absorption, and dry density were considered for process optimization. Finally, for process validation, various PQC performance parameters (fresh, mechanical, and durability) were determined. The findings suggest soaking the RCA sizes in any of the considered cementitious/waste material slurry at 40% concentration for 6 h for enhanced performance of both RCA and PQC made with treated RCA. (c) 2023 American Society of Civil Engineers.