Impact of recycled aggregate and waste glass on microstructure properties of concrete

This research paper investigates the effects of recycled aggregate (RAC) and waste glass (WG) on the microstructure of concrete, where RCA replaces natural coarse aggregate and WG replaces natural fine aggregate. The experimental program evaluated six replacement percentages (0%, 10%, 20%, 30%, 40%, and 50%) for RCA and WG in concrete mixtures. In the present work the characteristics of the Interfacial Transition Zone (ITZ) and the formation of the hydration products were investigated by the Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD), respectively. Based on the microstructural analyses, concrete mixtures incorporating RCA and WG up to 30% as coarse aggregate and fine aggregate replacement exhibited improved ITZ characteristics and enhanced hydration product development. This optimal combination resulted in a micro-hardness increase of 22% compared to normal concrete. However, replacement levels exceeding 30% adversely affected ITZ quality and reduced the volume of desired hydrate formation. The findings provide valuable insights into the economical use of recycled materials in concrete, emphasizing their potential to achieve specific microstructural properties.