The role of magneto-induced fiber distribution and orientation in the rheological behavior of steel fiber-reinforced cement mortars

Steel fiber-reinforced concrete is a promising magneto-responsive (MR) cementitious material. In this study, the rheological behavior of cement mortars with steel fibers after magnetic exposure was systematically investigated. The effects of fine sand, steel fiber content and geometries, and superplasticizer dosage were studied using a modified flow table test. The results indicate that after exposure to a 20-second magnetic field, the steel fiber-reinforced cement mortars exhibit significant anisotropic spread flow, characterized by a reduced diameter parallel to the magnetic field direction and an increased diameter perpendicular to it. To quantitatively examine the magneto-induced fiber motion within the mortar, the relationships between rheological properties, MR flow behavior, and fiber distribution and orientation were then analyzed. Based on the experimental results combined with observations of fiber motions in a transparent medium, three primary factors, including the diversion effect of fiber orientation, residual magnetization in fiber networks, and the restricting effect caused by localized fiber aggregations, were proposed as key contributors to the directional flow behavior. The findings validate the feasibility of steel fiber-reinforced mortar as a responsive material for magneto-rheology control, and further provide valuable insights into the influences of fiber distribution and orientation on the radial flow behavior of cementitious systems. • Steel fiber-reinforced mortars exhibit anisotropic spread flow under magnetic field. • The flow spread is reduced in direction parallel to the magnetic field. • Relations between medium rheology, MR flow, and fiber orientation are analyzed. • Three primary factors are proposed to explain the directional flow behavior.