Surface Processing of Shotcrete 3D Printed Concrete Elements Using a Rotating Trowel Disc – Influence of Timing on Resulting Surface Quality

As Additive Manufacturing in Construction (AMC) continues to gain attention across the building industry, challenges regarding its application and quality assessment are increasingly relevant. The surface quality of printed elements is particularly important, as it determines the aesthetics and is among others, a crucial aspect when compared to traditional cast concrete components. However, these aesthetics vary for individual AMC processes. For deposition processes, the surface is characterised by a clearly visible layer structure This layer structure is additionally characterised by an overlaid rough structure for material jetting processes such as Shotcrete 3D Printing (SC3DP). This surface can be finished through post-processing to achieve a smooth surface or a defined texture for functional integration. For this purpose the present research investigates an innovative surface post-processing technique based on a rotating trowel disc. Experiments are performed on a wall segment produced with SC3DP, focussing on evaluating the influence of three different waiting times after printing before starting surface post-processing (10, 45 and 90 min). Penetration tests are used to determine the yield stress of the printed material for each post-processing time. The resulting surface roughness is analysed by determining the mean profile depth and the estimated texture depth. Results indicate an overall feasibility of the investigated post-processing technique. Especially the reduced structural build-up at the edges compared to the centre of the shotcrete 3D-printed strands allows for a large process window for surface finishing. In this context, delayed processing of the surface up to 90 min after material application results in a smoother surface than early processing.