■3■3）t■4） 4）（p■=2pt■3h■■）=■=■t123Q■=+-■ ■=,4, （Plastic viscosity ■■hrheological quantities. Those shown in Table 3 include the followings: the flow rate measured by the pipe viscometer QA; the pressure gradient ΔP/l for each case; the water film thickness estimated by the pressure dehydration test y; the water film flow rate by Equation (4) QW; the slip velocity Vr; and, the Bingham fluid flow rate QB obtained by subtracting the flow rate due to slip QS and the water film flow rate QW from the measured flow rate QA. The water film thickness shown in Table 3 was extremely small between 0.000116 to 0.000164cm, which resulted in the extremely low water film flow rate between 0.108159 to 0.266205cm3/s.Equation (5) for the Bingham fluid flow rate can be simplified as Equation (8), with the pressure gradient Δp/l=i:By solving the following three simultaneous equations rearranged from Equation (5) with the Bingham fluid flow rate values shown in Table 3, plastic viscosity and yield stress can be obtained as expressed by Equations (9) and (10):Yield stress (8)(9)(10)cylinder with a radius of 20cm and a height of 20cm and an outer cylinder with a radius of 30cm and a depth of 40cm. With the rotational speed of the inner cylinder increased from 5rpm to 50rpm by 5rpm, torque was measured at each rotational speed, and plastic viscosity and yield stress were Table 3 Estimated Bingham fluid flow rate based on the flow rate measured by the pipe viscometerUnit water content W （kg/m3）Mix No.160165170■■（■■-p8h■■（3）（=Table 4 shows the calculation results of the plastic viscosity and yield stress in comparison with those measured by a rotational viscometer. The coaxial cylindrical rotational viscometer (Fig. 6) used in the experiment had an inner Pressure gradient Measured flow rate QA （cm3/s）ΔP/l （Pa/cm）169.1220.9263.0222.7260.0295.3178.5252.1103.04608.35342.76335.87435.38663.89482.85993.68574.23503.5■■-3h■■■■（-p8■）■■■-■8Estimated water film thickness y （cm）0.0001330.0001170.0001160.0001590.0001580.0001520.0001590.0001610.000164Table 4 Calculation of the plastic viscosity and Rotating viscometerPlastic viscosity （Pa･s）1419086─ 6 ─ηpl τf ηpl’ Water film flow rate QW （cm3/s）Slip velocity Vr （cm/s）0.1171100.1176410.1380410.2199650.2546370.2662050.1777880.2555740.10815956.164.376.088.3102.6111.871.1101.242.1yield stressPipe viscometerYield stress Plastic viscosity Ratio η’/η1.001.011.00（Pa）（Pa･s）9771641419186Fig. 6 Rotational ViscometerBingham fluid flow rate QB （cm3/s）204.6294.6367.8502.4603.7699.7412.2622.1196.9Yield stress Ratio τf’/τf0.990.951.00（Pa）966864τf’
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