Effects of carbonated recycled sand on the interfacial bonding performance of 3D printed cement-based material

The layer-by-layer stacking process of 3D Printing Construction Technology (3DPCT) inevitably leads to weak bonding areas between the interlayer interfaces and the interstrip interfaces, which affect the mechanical properties of the printed structure. The effects of different carbonation time of recycled sand on the mechanical properties and interfacial bonding performance of 3D printed cement-based material with a 100 % replacement rate of carbonated recycled sand (3DPCRS) were explored. Although, the carbonation time of recycled sand affected the mechanical anisotropy of the printed specimens, the carbonation treatment of recycled sand cannot eliminate the mechanical anisotropy of 3D printed specimens. With the extension of the carbonation time of recycled sand, the interfacial bonding performance was gradually improved. At 28 days, the interlayer shear strength and interstrip shear strength of T7 group increased by 21.5 % and 18.7 %, respectively. After the carbonation of recycled sand, the indentation modulus of the interlayer interface was increased with the decrease of interface width and porosity, which improved the pore structure and the mechanical properties of the printed specimens.