Determining the load-bearing capacity of the layers in 3D printing mortars

Abstract

This research aims to assess the sensitivity and repeatability of the Unconfined Uniaxial Compressive Test (UUCT) for characterizing fresh mortars used in 3D printing. Based on the test results, load-bearing capacity was simulated under practical conditions to determine the maximum printable height as a function of different levels of layer deformation. The experimental program included six mortar formulations with variations in the water/binder ratio and sand content. The mixtures were tested for axial compressive strength at four hydration times (15, 30, 60, and 90 minutes), resulting in 24 experimental conditions. Method repeatability was verified using 12 replicates of a single condition. The results demonstrated that the UUCT is sensitive to behavioral differences among mortars, with adequate accuracy and repeatability, achieving a coefficient of variation of 6%. Simulations indicated that the mortars supported deformations ranging from 10% to 24%, corresponding to maximum printable heights between 0.63 and 1.67 m. Therefore, the UUCT proved to be an effective tool not only for mortar characterization but also for planning and predicting on-site behavior in real-scale 3D printing applications.