The vast majority of applications of extrusion-based concrete additive manufacturing deal with unreinforced mortar. The lack of reinforcement is a serious limitation for the industrial development of 3d printed concrete, because of the brittleness and lack of tensile strength of unreinforced mortar. In this paper, a new reinforcement method inspired by pultruded composite manufacturing, called flow-based pultrusion (FBP), is described and used. The principle is that continuous fiber rovings are impregnated and pulled by the matrix flow, avoiding motorisation, and increasing the apparent yield stress of the mortar and consequently its usability. The hardened resulting material, called anisotropic concrete, is unidirectionally and homogenously reinforced. For such composite material, the reinforcement ratio is an important material parameter that relates to specific process variables: roving type, roving count, and output diameter. This article further investigates the effect of the percentage of reinforcement on the process. It also highlights technical requirements to provide the first specifications for flow-based pultrusion.