Sustainable use of 3D-printed plastic waste as aggregate in self-compacting mortar: A study on rheological, mechanical and thermal performance.

Plastic waste poses environmental and health risks, highlighting the need for sustainable reuse in construction. This study introduces a novel solution to plastic waste utilization by: (1) developing rheological testing equipment from plastic using 3D printing technology, and (2) enhancing the rheological performance of self-compacting mortar (SCM) with 3D-printed plastic fine aggregates (3DPFA). SCM mixtures incorporating 5%, 10%, 15%, and 20% 3DPFA as a replacement for natural sand were prepared and tested to evaluate fresh, mechanical, and thermal properties through mini-slump flow, T20 spread time, J-ring flow, V-funnel, compressive strength, UPV, and thermal conductivity tests. Results revealed that incorporating 3DPFA significantly enhanced workability and flow characteristics. The mini-slump spread increased progressively with higher 3DPFA content, showing a 6% improvement at 20% replacement compared to the control. T20 flow time decreased markedly, reaching 2 s at 20% 3DPFA, indicating improved flowability. Similarly, J-ring tests demonstrated enhanced passing ability, with increased spread and reduced height differences, maintaining slump flow differences within acceptable limits. V-funnel flow time reduced from 7 s in the control mix to 5 s with 20% 3DPFA, confirming improved viscosity and flow dynamics. Furthermore, thermal conductivity showed a substantial reduction of up to 22%. These findings highlight a promising pathway for plastic waste valorization in the construction sector.