Evaluation of various treatment methods for enhancing the physical and morphological properties of coarse recycled concrete aggregate

The main objective of this research is to enhance the physical and morphological properties of coarse recycled concrete aggregate (CRCA) by combining different types of treatment methods. Heat treatments included various temperatures (250°C, 350°C, 500°C and 750°C). Presoaking method involved the use of strong acid HCl and weak acid C2H4O2, whereas short mechanical treatment included the utilization of a Micro-Deval device. In order to investigate the surface morphology and chemical composition for both treated and untreated CRCA, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analyzer (EDAX) analyses were also conducted. The obtained results indicated that the combination of heat treatment at 350°C and short mechanical treatment led the best performance for enhancing physical properties, with more than 27% lowering of water absorption. The use of weak acid treatment is an effective, safe and more preferable may than strong acid. Heat treatment appears to have negative effects when used at higher temperatures (500°C and 750°C). A large microstructure enhancement was obtained that particularly includes increased density, increased surface homogeneity and a reduced Ca/Si ratio. Physical properties of CRCA including porosity and water absorption are strongly related to the durability characteristics in terms of resistance to freezing and thawing and resistance to abrasion loss under impact of heat treatment. Mineralogical characteristics in terms of Ca/Si ratio are strongly correlated with durable and mechanical properties including abrasion loss and adhered mortar loss under influence of heat treatment.