A review of rheological properties and influencing factors of 3D printed concrete

3D printed concrete has the advantages of green environmental protection, efficient and intelligent production, labor saving, and no formwork, and is one of the important ways to promote the industrialization and upgrading of the construction industry to intelligent and digital development. Corresponding to the three important stages of 3D printing for concrete: Pumping, extrusion and construction, the printability that determines the success of its preparation mainly includes pumpability, extrudability and buildability. However, there are contradictions and balances between these characteristics, and they are closely related to rheological properties. Therefore, the rheological properties of concrete are vital important factors for 3D printed concrete, and it is also the main factor restricting the wide application of 3D printing technology in civil engineering. At present, there are many researches on the rheological properties of 3D printed concrete, however, there is still no comprehensive understanding for the key research directions such as the test scheme and influencing factors of the rheological properties of 3D printed concrete. Therefore, this paper first reviewed the test protocols, measuring ranges and models for rheological parameters (yield stress, plastic viscosity and thixotropy) of 3D printed concrete. Secondly, the factors affecting rheological properties of 3D printed concrete were analyzed, influencing factors include raw material properties, mix proportion, printing parameters and temperature, and the method of controlling rheological parameters is obtained. Finally, the problems in the research of 3D printed concrete rheological properties are pointed out and improvement measures are proposed, as well as its development trend and application prospect are prospected.