Combined printable and mechanical analysis of 3D-printed green high-strength, lightweight engineered cementitious composites

Abstract

This study used a novel eco-friendly lightweight sand fine (LSF) to prepare green lightweight and high-strength ECC (GLH-ECC) for 3D printing. Orthogonal design, analysis of variance, and analytic hierarchy process were first employed to explore the influence of water-to-binder ratio (WBR), LSF replacement rate (LRR), and fiber volume content (FVC) on the printability of ECC fresh mortar. The influence degree of three factors on the fluidity, consistency, and setting time of fresh ECC was FVC >WBR >LRR, LRR> FVC > WBR, and WBR> LRR >FVC, respectively. Besides, the scopes of fluidity, consistency, and setting time for ensuring the favorable printability of fresh GLH-ECC were 172–183 mm, 7.4–8.0 cm, and 5.3–5.9 h, respectively. A novel mechanistic parametric model was developed to establish a direct correlation between the fluidity, consistency, setting time, and buildability of GLH-ECC. Additionally, higher effective fiber content along the direction of printing and incorporated LSF in printable GLH-ECC provided more appropriate interfacial bonding between the fiber and matrix and resultant better fiber bridging ability, in contrast to the casting ECC. Moreover, the fiber orientation in the printable GLH-ECC tended to be arranged along the direction of printing, and the well-organized fiber orientation and more matrix pores in the interlayer interface of printable GLH-ECC led to the notable anisotropy of mechanical properties. This study inspires applications of 3D-printed GLH-ECC in digital construction without reinforcement in terms of excellent printability, impressive mechanical properties, light weight, and effective waste utilization.