Eco-optimization of sugarcane bagasse ash-based 3D printable concrete using response surface modelling

3D concrete printing (3DCP) is increasingly being explored as an alternative construction technique because it avoids the use of conventional formwork and allows structures to be built through direct deposition of material in successive layers. In recent years, a large amount of research has focused on developing printable cementitious mixes that can ensure smooth extrusion, adequate buildability, and satisfactory mechanical performance. At the same time, there is a growing interest in using waste materials in printable concrete to improve sustainability. The present work investigates the performance of extrusion based 3D printable concrete, incorporating 40% sugarcane bagasse ash (BA) as a partial replacement of cement. An experimental investigation was carried out to evaluate the influence of High water reducing admixture (HWRA) and Viscosity Modifying Admixture (VMA) on fresh and hardened properties of the 3D printable mix. Key parameters such as flowability, extrudability, buildability and compressive strength were examined to assess the suitability of the mixes for 3D printing applications. A quadratic regression-based response surface modelling approach was adopted to establish second-order prediction equations for estimating compressive strength at 7 and 28 days. The results indicated that the developed models showed good agreement with experimental data, with coefficient of determination values exceeding 0.90. The optimum dosage of HWRA and VMA for both conventional and BA based mix is 1.0% and 0.4% respectively. The conventional mix achieved a 28-day compressive strength of 53.81 Mpa, whereas the bagasse ash mix attained 44.22 Mpa, which is approximately 18% lower than the conventional mix but remains within an acceptable range for structural applications. The study demonstrates that sugarcane bagasse ash can be effectively utilised in 3D printable concrete, contributing to sustainable construction while maintaining adequate performance. The proposed RSM-based approach provides a practical framework for 3D printable mix.