In this paper, a novel extrusion-based 3D printed material was obtained by preparing 3D printed recycled coarse aggregate concrete (3DPRAC) using recycled coarse aggregate (RCA), and the compressive and flexural properties were investigated at different RCA replacement ratios, ages, and construction forms. The porosity, pore volume distribution, pore geometry characteristics were analyzed by X-CT. MIP and SEM were used to analyze the pore structure of the RCA. The results showed that the compressive and flexural strengths have obvious anisotropic characteristics. With increasing replacement ratio, the compressive and flexural strengths generally decreased. Internal pores of 3DPRAC were found to exhibit the geometric characteristics of flat ellipsoidal and uniaxially oriented arrangements along the printing direction. A multiple partition-interface model was proposed to establish the connection between pore structure characteristics and force cracking, and the anisotropic mechanical property mechanism of 3DPRAC was revealed.

本文采用再生粗骨料 (RCA) 制备 3D 打印再生粗骨料混凝土 (3DPRAC)，获得了一种新型挤压型 3D 打印材料，并研究了不同 RCA 替代率、年龄和施工形式。用X-CT分析了孔隙率、孔体积分布、孔几何特征。MIP和SEM用于分析RCA的孔结构。结果表明，抗压强度和抗弯强度具有明显的各向异性特征。随着更换率的增加，抗压强度和抗弯强度普遍下降。发现 3DPRAC 的内部孔隙沿打印方向呈现扁平椭圆体和单轴取向排列的几何特征。