Quantitative surface quality evaluation for 3D-printed concrete with coarse aggregate through 3D scanning

The undulating appearance of 3D-printed concrete (3DPC) is an essential feature that impacts the integrity and stability of the multilayer structure, yet the related evaluation parameters have rarely been proposed. This study proposed a quantitative evaluation and parameters through the on-site 3D scan technology to impel a direct and precise understanding of the surface quality of 3DPC, especially concrete with coarse aggregates. Firstly, 8-layer 3DPC walls are produced at four different printer printing rates and then 3D scanned. After point cloud correction, noise reduction, and 2D processing onto acquired points cloud, the evaluation parameters for evaluating 3DPC surface characteristics are defined and calculated. Results indicate that a higher 3D printer printing rate helps reduce surface fluctuation of 3DPC multilayer structures but disfavor the vertical flatness, of which the linear relationship between the parameters and the printing speed of the printer is explored and discussed. Recommendation of 3DPC straight wall structures controlled to surface defects ratio within 2% and slope within 0.2% is suggested. These conclusions provide precise external surface quality control and treatment basements that contribute to improving the practical application of 3DPC.