Exploratory study on the rheological behaviour of 3D printable mortars incorporating fine recycled concrete aggregates (FRCA)

This study investigates the rheological behaviour of 3D-printable mortars incorporating fine recycled concrete aggregates (FRCA), focusing on the influence of 25% and 50% FRCA substitution on key rheological parameters, such as flow spread, penetration resistance, shear stress, and yield stress over time. Rheological tests were conducted at 20, 40, and 60 minutes to capture the time-dependent behaviour of the mixtures. The flow spread test evaluated the mortar’s consistency and ability to maintain workability over time, essential for continuous extrusion during the printing process. The penetration resistance test assessed the stiffening rate of the mortar, providing insights into setting time and early strength development. The vane and slug tests measured yield stress, a critical parameter for ensuring buildability and layer stability, indicating the mixture’s capacity to support subsequent layers without deformation or collapse. The results from the reference mixture were used to compare the performance of mortars with 25% and 50% FRCA content, highlighting the impact of recycled aggregates on time-dependent rheological properties. Mortars containing FRCA exhibited differences in flow retention and yield stress evolution, which are key factors influencing extrudability and printability in additive manufacturing processes.