Real time control of fresh cement paste stiffening: Smart cement-based materials via a magnetorheological approach

Abstract

A smart cement-based magnetorheological (MR) fluid, one that could be tailor-designed to yield the desired rheological properties of cement paste, in real time is presented. By incorporating magnetic particles inside the cement paste and by varying the magnitude of the magnetic field strength, the rheological response of the sample is altered significantly. This cement-based MR fluid would allow for better control over stiffening/setting behavior of concrete and can be useful in applications in which controlling the fresh-state behavior of concrete is critical. In this work, magnetic fields were altered in a low-high-low and high-low-high pattern to assess the effect of cyclic variations of the magnetic field on the rheological behavior. It was found that a cement-based MR fluid does exhibit field sensitivity in its rheological behavior when the magnetic field is varied. At early ages, when the magnetic field is varied, the rheological behavior was seen to be less dependent on the time frame at which the magnetic field is applied and more related to the magnitude of the magnetic field. At later ages, in the presence of a cyclic magnetic field, the rheological response will be influenced by the magnetorheological response and by aging mechanisms (e.g., hydration and thixotropy) that impact the stiffening of cement paste.