Performance evaluation of limestone-blended cement and cellulose nanomaterials in 3D concrete printing

Three-Dimensional Concrete Printing (3DCP) has emerged as a transformative technology to enhance efficiency, productivity, and safety in construction. However, the high cement content typically used in 3DCP presents sustainability challenges. This study explores the potential of low-carbon and sustainable materials, specifically portland limestone blended cement (GULb) and cellulose nanomaterials, to meet both rheological and mechanical performance criteria while addressing environmental concerns. The response surface methodology was employed to statistically evaluate the effects of water-to-binder ratio ( w/b : 0.30–0.38), nano-fibrillated cellulose (NFC: 0–0.25%), and cellulose nanocrystals (CNC: 0.05–0.15%) on the properties of 17 GULb-based 3DCP mixtures. Key performance indicators included flowability, yield stress, setting time, compressive strength (in both horizontal and vertical directions), and interlayer bond strength. Thermal and microstructural analyses complemented these assessments to validate the observed trends. At a w/b of 0.38 and higher dosages of NFC (0.25%) and CNC (0.15%), superior rheological properties, mechanical strength, and interlayer adhesion were achieved. Numerical optimization revealed that GULb-based 3DCP formulations modified with cellulose nanomaterials can satisfy rheological requirements while achieving a balance of mechanical and interlayer properties. However, the optimum material proportions vary depending on specific design targets.