Performance Evaluation, Microstructure Behaviour and Life Cycle Assessment of 3D Concrete Printable Ink Containing Recycled Construction Waste (2026-04)¶

This study investigates the feasibility of incorporating recycled construction waste (RCW) in the form of recycled fine aggregates (RFA) and recycled coarse aggregates (RCA), along with supplementary cementitious materials (SCMs), in the development of M30-grade 3D concrete printable (3DCP) inks. Investigation carried out to optimize 3DCP inks with aggregate-to- binder (a/b) ratio from 0.5 to 2.0 at intervals of 0.5. Furthermore, SCMs, namely fly ash and ground granulated blast furnace slag (GGBS), were incorporated at replacement levels ranging from 15% to 30% in 5% increments. In contrast, RFA and RCA replacements varied from 0% to 100% in 20% increments, respectively. Microstructural characterization of raw materials and ink compositions was conducted to assess their suitability for structural applications. Research investigates the fresh and hardened properties of 3DCP inks, including extrudability, printability, buildability, mechanical and thermal properties of 3DCP inks. In addition, a comprehensive Life Cycle Assessment (LCA) was performed to quantify the environmental impacts of 3DCP inks. Findings shows that 3DCP ink containing optimized replacement level of fly ash (15%), GGBS (25%), RFA (40%), and RCA (40%), with a/b ratio of 1.5 and w/b ratio of 0.35, meets the standards of rheological and 3DCP performance, achieving a flow value, yield stress, shape retention and buildability ratio of 165 mm, 1.75 kPa and 99.7%, respectively. Although 3DCP ink met the required strength properties of M30 grade concrete, a strength reduction of 23% was observed compared to control. LCA findings demonstrated substantial reductions in global warming potential (39.05%), acidification (35.50%), and ozone depletion (38.82%). In a nutshell, research outcomes indicate significant environmental benefits have been achieved without compromising the standard performance requirements of 3DCP inks and improved finish surfaces of printed elements. This study paves the way for potential utilization of recycled construction waste in 3DCP inks to build structural elements sustainably and promote sustainable construction practices.