Weak Inter-Layer Bonding in Extrusion 3D Concrete Printing (2021-01)¶

Recently, there has been meaningful progress towards the construction threedimensional printing (3DP) of concrete (3DCP). However, weak inter-layer bonding (ILB) in extrusion 3DCP is a constraint that can critically influence the mechanical capacities, the stability of the structures, and durability. Various techniques have been proposed to mitigate weak ILB. Though, these techniques do not systematically address the basic causes of weak ILB and display inconsistency of the results. Additionally, the scope of the testing has been rather limited. Here, an approach for the mitigation of weak ILB is proposed, as part of ongoing research. It is based on stabilizer mortars (SMs) of varying mix compositions, according to the printing time interval (TI). This study compares mitigation techniques based on the statistical analysis (Chebyshev theorem, T-test, and standard error) of the test data against a 90% confidence interval. The proposed technique demonstrated peak mitigation of weak ILB with less variation in test results at extended TI up to 120 min. Besides efficacy, the simplicity of the technique i.e. practicality of the method and the materials cost, availability, safety, and sustainability remain ideal.