Optimization of biopolymer additives for 3D printable cementitious systems: A design of experiment approach

This study delves into the utilization of biopolymers in the burgeoning domain of 3D concrete printing. Diverging from traditional oil-based chemical admixtures, the potential of biodegradable additives, including corn starch (CCS), methylcellulose (MC), and xanthan gum (XG), as rheology modifiers were explored. To address this challenge, a response surface methodology was employed to achieve optimized mixes with different combinations of these biopolymers with superior rheology and printability. The response surface methodology suggested a hundred different optimized combinations. Four of them were selected based on their rheological parameters for further evaluation. These mixes are defined as M1 (CCS-2%, MC-2%, XG-2%), M2 (CCS-0%, MC-2%, XG-2%), M3 (CCS-1.67%, MC-1.69%, XG-1.12%), and M4 (CCS-1.92%, MC-1.34%, XG-1.35%) based on different contents of CCS, MC, and XG. Non-contacting digital image correlation was employed to assess the buildability and green strength of the optimized mixes. The results revealed that these rheology modifiers tailored the rheology, green strength and printability parameters (extrudability, buildability), which affirmed the efficacy of biopolymers in additive concrete manufacturing. However, the higher contents (2%) of MC and XG displayed retarding effects resulting in the slower development of green strength even at t=60 and t=90 mins. The peak stress values for green strength at t=90 mins were recorded as 0.594, 0.728, 1.628, and 1.331 kPa for optimized mixes M1, M2, M3, and M4, respectively. • The reuse of bio-wastes and sustainable materials in construction was investigated through the application of biopolymers (methylcellulose, corn starch, and xanthan gum) as viscosity modifiers in 3D concrete printing. • The study emphasizes low-carbon construction materials, specifically optimized for 3D printing of infrastructure applications, aligning with sustainable construction practices. • Mix optimization was conducted using the Design of Experiment technique, specifically Response Surface Methodology, to enhance material performance. • Printability characteristics, including extrudability and buildability, were evaluated, with non-contacting digital image correlation employed to assess layer deformation over time. • While optimization improved printability and green strength, higher biopolymer content delayed early-age strength development, highlighting a balance between sustainability and material performance.