Conventional casting and placement of concrete involves fragmented tasks such as reinforcement arrangements, formwork assembling and dismantling later, and concrete pouring. Recent study on the automation in construction reports that the fragmented construction can be possibly replaced by continuous operations such as 3D printing. The use of continuous operations can reduce the time of construction and consequently construction expenses. Control of the rheology of fresh cement-based materials is the key technology to realize the continuous casting of cement-based materials. Various precursors of 3D printing are summarized, and basic understanding toward the continuous casting is provided in terms of the rheology.