An overview of 3D printed concrete for building structures: Material properties, sustainability, future opportunities, and challenges

Three-dimensional (3D) printing of concrete structures is gaining interest and popularity as an alternative to conventional construction. 3D-printed concrete (3DPC) is advantageous for constructing building elements or structures with complex geometries, as it generally decreases construction time, can reduce costs, and improves safety on construction sites. Compared to concrete for conventional construction, mixes for 3D printing must satisfy more stringent requirements to achieve pumpability, extrudability, and buildability. This study reviews the rheological, mechanical, and durability properties of mortar-based 3DPC. The effect of incorporating coarse aggregates in 3DPC mixes on the shrinkage and bond strength of printed elements is also discussed. Mortar-based 3DPC is characterized by a lower self-weight which enhances interlayer stability. However, mortar-based 3DPC exhibits high shrinkage compared to aggregate-based 3DPC. Both a retarder and high-range water-reducing admixtures may be necessary to control the flowability and setting time of 3DPC. The study focuses on the effects of binder composition, aggregate size, water-to-binder ratio, reinforcement, and printing parameters on pumpability, extrudability, and buildability. Selected aspects related to 3D printing of concrete including material properties, applications, sustainability, challenges, and future opportunities are discussed.