Determination of Optimal Flowability of 3D Printing Concrete Based on Multi-objective Optimization Method

Flowability is a crucial factor affecting the performance of 3D printing concrete. Based on flowability test results, materials suitable for 3D printing can be quickly screened, making it essential to determine the appropriate flowability to optimize the performance of 3D printing concrete. This study maintains constant water-cement ratio, sand ratio, and particle gradation, and adjusts the content of superplasticizer to control the flowability of the concrete mixture. Several performance tests were conducted to analyze the variations in extrudability, buildability, and thixotropy of 3D printing concrete with changing flow-ability. Different evaluation factors are established to quantify the optimal and poor range of extrudability, buildability, and thixotropy. Based on these factors, multi-objective optimization was performed using NSGA(Non-dominated Sorting Genetic Algorithms)-II coupled with the AHP(Analytic Hierarchy Process)-Entropy method to determine the flowability range that ensures good performance.
The results show that flowability significantly influences the performance of 3D printing concrete. When the flowability is maintained at 170-180mm, it ensures smooth extrusion and successful printing, meeting the requirements of extrudability, buildability, and thixotropy to the greatest extent. This study provides theoretical basis and practical guidance for the material design and performance optimization of 3D printing concrete.