Numerical method for thixotropic behavior of fresh concrete

The thixotropic characteristic or rest & shearing time-dependence of fluidity of fresh concrete has an influence on its production and construction processes. In this paper, the mechanisms of the thixotropy and rest & shearing time-dependence were discussed, followed by proposing an analytical approach to numerical prediction of the rest & agitating time-dependent flow behaviors on the basis of Discrete Element Method (DEM). In this new DEM, the effects of cement hydration, physical flocculation of cementitious particles, and agitation were taken into account. To validate the numerical method, the rheological tests of fresh mortars with or without mineral admixtures were performed after the mortar samples stood still for different times, using the B-type viscometer, of which the rotor's rotation would break down its surrounding particles' flocculation structure. The numerical results of toque-rotational speed relationship were close to the experimental results.