Hydration and rheology control of concrete for digital fabrication: Potential admixtures and cement chemistry

Concrete digital fabrication is an innovative construction approach where infrastructural elements can be built additively without using formwork. This represents a significant advantage, but also introduces materials engineering challenges, as the requirements normally fulfilled by the formwork are now imposed on the concrete. In this paper, it is discussed how admixtures can be employed to achieve the rheological and hydration properties necessary for printable concrete. An overview of various admixtures currently implemented in standard practice is presented. Then, the main required concrete states for extrusion and deposition processes are analyzed with respect to required performances and potential admixtures. Finally, possible side effects and incompatibilities are discussed, as well as how they could be unconventionally used for printable concrete purposes. The main objective is to demonstrate how admixtures will be critical in the development of concrete systems to realize digital fabrication, and to ultimately motivate investigation in the key areas discussed.