PURPOSE: To enable the continuous and smooth feed of ready-mixed concrete under pressure without causing the biting of an aggregate by making one surface of the valve body of a three-way open/close valve like a circular arc form, and constituting the body as a rotary valve of crescent section having a sharp part at both ends thereof.

CONSTITUTION: Valve bodies 21a and 21b constituting a three-way open/close valve having one surface formed like a circular arc and a crescent sectional form with a sharp part at both ends are so provided as be freely rotatable in valve boxes 2a and 2b under the bottom outlet 1a of a hopper 1. Valve cylinders 5a and 5b are provided at the sides of the valve boxes 2a and 2b, and the rods 6a and 6b of the valve cylinders 5a and 5b are connected to support shafts 22a and 22b via support levers 7a and 7b. Due to the telescopic motion of the rods 6a and 6b, therefore, the support shafts 22a and 22b turn, thereby causing the open and close operation of the valve bodies 21a and 21b constituting the three-way open/close valve.