Influence of Polyethylenimine (PEI) in enhancement of microstructure and surface morphology of recycled construction and demolition waste aggregate in concrete by carbonation

This investigation explores the influence of Polyethylenimine (PEI) on the improvement of carbon dioxide (CO2) uptake, surface texture, and pore structure of construction and demolition waste (CDW) through carbonation. The study focuses on the coarser fraction of CDW (10 mm), which is pre-treated with varying concentrations of PEI before being carbonated. The resulting changes in pore structure, mineralogical composition, physical properties, and surface morphologies of the CDW are characterized using various techniques. The study also evaluates the impact of carbonated CDW on compressive strength. The results indicate that PEI modification of CDW enhances carbonation efficiency by reducing pores more effectively than non-treated CDW. This microstructural refinement is possible due to the formation of calcite and its products, facilitated by PEI adsorption into CDW, enhanced CO2 uptake, and formation of calcite products through carbonation. Additionally, PEI modification results in the formation of undulated plate-like structures that enhance surface morphology and compressive strength when used in concrete. The carbonation behavior of PEI-modified CDW in concrete was also investigated by analyzing carbonation depth and pH value. The results reveal that the optimal PEI concentration for enhancing the performance of CDW is 0.2. Overall, the study highlights the potential of PEI modification as an effective approach to improve the properties of CDW and its potential as a sustainable construction material.