Shrinkage behaviour of 3D-printed walls under restrained conditions – an experimental and numerical investigation

Shrinkage-induced cracking is frequently observed in 3D construction printing (3DCP). Beyond aesthetic concerns, such cracking can compromise the structural performance and durability of 3D-printed elements. Because high early-age shrinkage occurs while the 3D-printable mortar/concrete has not yet developed sufficient tensile strength, restrained 3D-printed structures are susceptible to early-age cracking. Previous studies have investigated this problem and explored shrinkage-mitigation measures such as early-strength enhancement and/or using shrinkage-reducing admixtures. However, the effect of restraint conditions on shrinkage-induced cracking encountered in 3DCP is less explored. Experimentally validated numerical models for analysing shrinkage-induced cracking in 3D-printed walls under different restraint conditions remain limited. In this study, the effects of end-restraint (e.g. columns) and edge-restraint (e.g. concrete slab) conditions on shrinkage-induced cracking were investigated using 3D-printed wall segments. The wall segments were printed and restrained to mimic these restraining effects, highlighting the localised tensile cracking and/or debonding. A finite-element modelling framework was established using experimentally measured time-dependent material properties and calibrated shrinkage inputs. Its strain predictions were validated against wall measurements, while stress-strength comparisons were used to assess regions of elevated cracking and interface-failure risk. The framework provides a basis for assessing shrinkage-cracking risk under the laboratory-scale conditions investigated and could inform future structural design approaches for 3D-printed walls.