Pozzolanic potential of recycled aggregates for 3D printed concrete

Abstract

The emerging technology of 3D concrete printing enables faster construction, complex geometries, and reduced on-site injury risks. Despite its benefits, it still relies heavily on cement. Incorporating recycled aggregate powder offers a promising strategy to lower environmental impact, though it poses challenges. Assessing the pozzolanic reactivity of these materials is essential, as they may contribute to mechanical and durability properties or act as inert fillers that enhance rheology and setting. This study investigates the pozzolanic activity and hydration behavior of recycled aggregate powder used to replace 50% of the binder and cement by mass in 3D-printed concrete. The experimental program included X-ray diffraction (XRD), thermogravimetric analysis (TGA), Frattini and Chapelle tests, setting time measurements, and the Strength Activity Index (SAI). Results show that the recycled material lacks significant pozzolanic activity. However, its influence on hydration and setting provides insights into its role as a filler in sustainable printable cementitious formulations. These findings underscore the importance of evaluating recycled materials before their application in additive manufacturing.