Effects of oyster shell derivatives on performance enhancement of biomass-based 3D printed concrete

Abstract

In this research, sustainable oyster shell derivatives were used as partial replacement of Portland cement-sulfate aluminate cement composite (OPC-SAC) composites to investigate the potential application in the mix-stir-extrusion integrated 3D concrete printing. Calcined oyster shell powder (CS) was added into OPC-SAC concrete at 0-15 wt% to prepare a new 3D printed concrete. Additionally, oyster shell particles (CSS) were substituted for river sand at 0-41.7 wt% as another new material. The effects of oyster shell derivatives on the forming mechanism and performance of 3D printed concrete were studied by macro and micro tests. The results demonstrate that the two new materials, which can be printed with an initial setting time within 15-36 min, exhibit superior overall performance compared to OPC-SAC, achieving an efficiency improvement of up to 75%. When the CS content was 15%, the formability of 3D printed concrete reached the best. The optimized compressive strength and flexural strength at 28 days surpassed 40 MPa, and 10 MPa, respectively. Micro-morphological analysis showed that CaO in CS facilitated the hydration reaction of concrete and generated more C-S-H gels and Aft crystals, which resulted in a denser bond between the substances and enhanced the mechanical strength. The above results indicated that both CS and CSS could improve the mechanical properties of OPC-SAC.