Evaluating the performance of recycled aggregate concrete incorporating 3D-Printed concrete waste as aggregate using the rebound hammer test

This study investigates the strength of recycled aggregate concrete (RAC) incorporating 3D-printed concrete (3DPC) waste as recycled aggregates over a year. With the growing adoption of 3DPC, recycling its waste presents a sustainable solution to mitigate environmental impact and conserve resources. The 3DPC waste was processed into recycled aggregates through a single stage crushing method using a jaw crusher, producing a mix of fine and coarse aggregates. These recycled aggregates were blended with the river sand at 50 %, and 67 % of the total aggregate content to produce C30/37 and C40/50 strength classes. The experimental program involved performing a rebound hammer test, a nondestructive testing (NDT) method, to estimate compressive strength while considering the effects of replacement ratio, aggregate type, specimen age, and surface temperature. The results were then validated with a standard compression test, a destructive testing (DT) method, to evaluate the reliability of the NDT approach. Findings reveal that density significantly influences RAC compressive strength, with strength increasing progressively over time. Surface temperatures above 30 °C moderately reduced estimated compressive strength, causing deviations of up to 11.5 %. RAC mixes with 50 % and 67 % recycled aggregates exhibited higher compressive strength, except for the C30-RA50 mix, which deviated from this trend. An empirical formula was developed using rebound hammer and standard compression results to predict RAC strength and was compared with existing curve equations. These findings provide a robust basis for improving NDT-based strength assessments of RAC and highlight the potential of utilizing 3DPC waste in sustainable construction practices.