Inversely estimating flow characteristics of geopolymer paste based on the MPH-I calculations

A method for inversely predicting the flow properties of Bingham fluid, i.e., yield stress and plastic viscosity of the geopolymer paste, from a simple dam-break experiment was developed based on the MPH-I ((Moving Particle Hydrodynamics for Incompressible flows) calculations. In the decommissioning of Fukushima-Daiichi nuclear power plant, geopolymer is one of the candidate materials for stabilizing the fuel debris and for sealing the PCV (Primary Containment Vessel), where it is important to predict and control the fluidity of the paste of the material. Therefore, the flow property is to be confirmed just before practically pouring the paste. In the inverse estimation, the MPH-I calculations are used only in the preparation phase to obtain the base curve of the front position history with respect to the various yield stresses. Then, both the yield stress and plastic viscosity are estimated using the base curve with an assumption that the inertial force is negligible. Since no additional calculation is needed in the prediction phase, it is applicable for the checking before the pouring. In this study, the methodology was tested against the geopolymer pastes with adding various amount of silica sand for enlarging viscosity. It was confirmed that the front position history obtained from the experiment was well reproduced by the predicted flow properties. This indicates that the Bingham parameters were inversely estimated well.