Possibilities of fly ash as responsive additive in magneto-rheology control of cementitious materials

Active rheology control, by means of pre-adding responsive additives and applying a trigger signal, is a potential approach to meet the contradicting requirements of concrete properties in different casting processes. In the present study, the possibilities of fly ash as responsive additive in magneto-rheology control of cementitious materials are examined from the viewpoint of early structural build-up of cement paste. Four different fly ashes with various particle sizes and magnetic properties are utilized. The magnetic properties of fly ash, characterized by saturation magnetization and magnetic fraction, are determined. Results reveal that the cement pastes containing fly ash exhibit apparent rheological response to an external magnetic field. The degree of the response depends on the magnetic properties and physical characteristics of the incorporated fly ash. Under the same volumetric replacement, the saturation magnetization of original fly ash is a useful parameter to describe the magneto-rheological effect of fly ash incorporated cement pastes. In comparison with the magneto-rheological response of cement paste with nano-Fe3O4 particles, the fly ash incorporated cement paste shows a longer period of dominating liquid-like properties. It is concluded that fly ash can be used as a responsive additive to improve the rheology of cement paste by applying magnetic field. (C) 2021 The Author(s). Published by Elsevier Ltd.