3D Printable Sustainable Binders Containing Indigenous Materials with Organic Additives Rheological, Mechanical Characteristics and Life Cycle Assessment

The global construction sector is shifting towards sustainability as concerns grow over the environmental burden of Portland cement. Ancient systems using lime and mud offer proven durability with significantly lower emissions. 3-dimensional(3D) printing presents a transformative opportunity to revive these materials, but challenges persist in adapting their rheology and structural performance for digital construction. This study proposes a novel blend of indigenous materials (lime, mud) and industrial waste, fly ash, modified with organic additives (rice-starch, jaggery, and myrobalan) to formulate an extrusion-friendly, high-performance composite for 3D printable ink. Morphological and elemental characteristics of the raw materials were examined using Field Emission Scanning Electron Microscope (FESEM) and Energy Dispersive X-ray Spectroscopy (EDS), supplemented by evaluation of their physical properties. Printable ink proportions (Plain, binary and ternary) were developed and evaluated for rheological and mechanical performance. Rheological behaviour was analysed via rotational rheometry, hydration kinetics through isothermal calorimetry. Extrudability was investigated through flowability, yield stress development and open time, followed by printability through layer width, continuity and layer height. Then, buildability was evaluated by layers’ total build height and shape retention tests, followed by assessments of compressive strength, ultrasonic pulse velocity (UPV), water absorption. Further, these findings are validated by FESEM and EDS and Fourier Transform Infrared Spectroscopy (FTIR) analysis. Finally, Life Cycle Assessment (LCA) was conducted using the ReCiPe Midpoint (H) method. Ternary printable ink(starch+Jaggery+Herada) (TPI) showed greater than 140% increase in yield stress over 105 min, maintaining required flowability, a key for buildability. Isothermal calorimetry revealed 24% higher cumulative heat release, indicating accelerated yet controlled hydration. The buildability of TPI achieved a buildability index (BI) of 0.98 for 15 printed layers and a shape retention factor (SRF) of 99.5%, which is 11.3% higher than that of plain printable ink (PPI). Mechanical testing showed an increase of 39% in compressive strength and improved UPV and thermal properties, supported by denser microstructure and enhanced pozzolanic reactions compared to plain ink. LCA results showed up to 50% reduction in Global warming potential (GWP100) CO2-eq emissions and energy demand compared to Ordinary Portland Cement (OPC) Ink. The study demonstrates a viable pathway to integrate indigenous materials with modern 3D printing technology, offering a sustainable, structurally sound solution that preserves traditional architectural identity and historical relevance.