Abstract: The slump test is well-established as a conventional method to estimate the yield stress of filling slurries, and its ability to predict yield stress based on the height of the slumped material by simply lifting the slump cone off the slurry at a low velocity has been studied extensively. However, determining the viscosity of slurries accurately using the same test remains a significant challenge. Given that the influence of viscosity on the height of the slumped slurry and the diameter to which it spreads is negligible at low lifting velocities (e.g., 0.01 m·s^–1), a modified slump test conducted with the cone lifted at a higher velocity (0.1 m·s^–1) is proposed in this study. A custom-designed slump apparatus was adopted to control the lifting velocity of the conical mold precisely, and the profile of the slumped slurry was measured using a laser rangefinder in each test. To systematically investigate the coupled effects of Bingham yield stress and viscosity on the slump height and spread diameter, numerical simulations were performed to analyze the slumping behavior of fly ash slurry under various combinations of yield stress and viscosity. The simulations specifically focused on conditions involving a mold with a high lifting velocity of 0.1 m·s^–1 to reveal correlations between the Bingham parameters on the one hand and the slump height and spread diameter on the other. Dynamic mesh techniques were applied along with the volume of fluid method to simulate the collapse process to acquire information on slumping behavior under arbitrary yield stress and viscosity values. The numerical results were validated against experimental data obtained from slump tests conducted at a low lifting velocity of 0.01 m·s^–1 and showed good agreement. In parallel, lubrication theory was applied to predict the profiles of the slumped slurry at different solid mass fractions, and these theoretical predictions also coincided well with the experimental measurements. The results of the simulation revealed several key trends. When the Bingham yield stress was held constant, the slump height decreased linearly with increasing Bingham viscosity. In contrast, although the spread diameter also decreased with increasing viscosity, the rate of reduction gradually diminished. When the Bingham viscosity was kept constant, the slump height decreased linearly with increasing yield stress. Meanwhile, the spread diameter exhibited an approximately linear decrease in the low-viscosity range but decreased nonlinearly in the high-viscosity range. Under conditions with high lifting velocity, the spread diameter showed more pronounced variations in response to changes in Bingham viscosity compared to slump height. Thus, this value was more sensitive as an indicator for characterizing variations in viscosity. Consequently, spread diameter was selected as the primary parameter to construct a predictive model of Bingham viscosity based on the results of the slump test. Four different versions of the predictive model for Bingham viscosity were developed, with each using a different regression method, including quadratic polynomial regression, random forest, eXtreme Gradient Boosting (XGBoost), and neural network models. The inputs to the models included the known spread diameter and Bingham yield stress. Among the four methods, the random forest and neural network models exhibited superior predictive performance with higher accuracy and better generalization capability. These findings validate the feasibility of using slump tests with high lifting velocity to predict the Bingham viscosity of mineral slurries. Given that the conventional slump test at low lifting velocity (0.01 m·s^–1) has already been applied to predict yield stress, the successful determination of Bingham viscosity using a modified slump test at a higher lifting velocity (0.1 m·s^–1) implies that complete characterization of both Bingham yield stress and viscosity can be achieved through just two sets of slump tests, with one performed at low and the other at high velocity. This dual-test approach offers a simple, rapid, and cost-effective alternative to conventional rheometers, which are often expensive and unsuitable for on-site or field applications.