Water Absorption Reduction of 3D Printed Concrete Using Silicones (2024-11)¶

The durability of concrete is often compromised by water and ion ingress. Water ingress through capillary suction is one of the mechanisms by which water and ions enter concrete. The porosity of 3D printed concrete is concentrated at the interlayer; therefore, the overall water absorption is increased at the interlayer. Several chemicals exist that reduce the water absorption of concrete. These chemicals are normally either applied to the casted concrete after curing or added integrally to the fresh concrete during mixing. Silicones are a chemical family that can be used either in post application or integrally, to reduce water absorption. While these silicones reduce water absorption, the pores remain open to water vapour and other gasses. Experiments were conducted to determine if silicones can reduce water absorption. Silicones were applied on top of each layer during the printing process. Silicones were also post applied to the side surface of hardened printed samples. The results show that both methods are suitable to reduce water absorption with the application between the layers lowering the overall absorption the most. However, the application between the layers did reduce the interlayer bond strength of the 3D printed concrete.