Ameliorating mechanical properties of treated mixed recycled aggregate concrete using a central composite design

The rapid expansion of global infrastructure growth has caused a substantial rise in construction and demolition waste. This study introduces an innovative approach for investigating mixed recycled aggregate in concrete generated from construction and demolition waste by treating it with cement and nano-silica slurry wrapping techniques. A central composite design experimental methodology was used to optimise the slurry for treatment, considering cement content, nano-silica content, and water-to-aggregate ratio as independent variables. At the same time, water absorption and Los Angeles abrasion with visual inspection were response-targeted values. Multi-objective response optimisation and desirability analysis determined optimal levels. Scanning electron microscopy, x-ray diffraction, and x-ray fluorescence were used to analyse mixed recycled aggregate facade changes after treatment. In addition, concrete with untreated and optimised treated mixed recycled aggregate at 0 %, 25 %, 50 %, 75 %, and 100 % as a replacement for natural aggregate was tested for workability and mechanical properties. The findings showed that 50 % replacement improved concrete characteristics at the optimal percentage due to the coating process-filled fracture holes and densified mixed recycled material, improving concrete matrix bonding.