Evolution of Capillary Pressure in 3D Printed Concrete Elements (2023-10)¶

In the initial hours following extrusion, 3D-printed concrete elements undergo intensive water evaporation. This process leads to significant negative capillary pressure within the system. During the period before solidification, this capillary pressure induces volumetric contractions, commonly referred to as plastic shrinkage, in the 3D-printed concrete, and as a result, causes cracking. Therefore, managing and forecasting the negative capillary pressure in freshly deposited concrete filaments is crucial to mitigating the effects of plastic shrinkage. In this study, the progression of capillary pressure in 3D-printed elements, with filament thickness ranging from 37.5 mm to 150.0 mm, was experimentally evaluated and numerically simulated. The numerical simulations utilised the extended Richard's equation. Shrinkage strains were empirically measured using 3D digital image correlation and compared with numerical outcomes. Additionally, we examined various combinations of parameters to analyse their influence on the accuracy of the numerical results.