Estimation of Magnetic Force between Micrometer-Sized Fly-Ash Particles in Cementitious Suspensions

Abstract

Magnetic fly ash is a potential alternative responsive additive to achieve magneto-rheology control of cementitious materials; it reduces the cost of magnetic particles and also is beneficial to preparing sustainable binder materials. This paper estimates the magnetic force between micrometer-sized fly-ash particles in cementitious suspensions. Four cases, regarding different selections of particle distance and different characterizations of magnetic properties of fly ash, are considered. The correlations between theoretical calculated parameters and experimental rheological properties are discussed. Results show that fly ash should be separated into magnetic and nonmagnetic parts to better estimate the magnetic force between particles. For the case of two neighboring magnetic fly-ash particles in cementitious suspensions, the estimated magnetic yield parameter, describing the relative magnitude of magnetic force to the resistance of the suspension, can be used as an indicator to describe whether the fly-ash cement paste shows rheological response to an external magnetic field. The intensity of the magneto-rheological response can be correlated to the average magnetic force calculated by considering the even distribution of magnetic fly-ash particles in nonmagnetic solid suspensions.