A fluid motor actuator, including a hydraulic cylinder, includes a cam which is extended to become engagable with a cam follower of an extension chute section which is hinged and folded within a first chute section during transport. When the cam engages the follower of the retracted extension chute section, the cam causes the extension section to pivot out of its retracted position so that both chute sections form a unitary elongated chute adapted for receiving and directing the flow of concrete from the bowl of the mixer to the construction site. The extension chute section is retracted when the pour is completed and the cam is moved to non-interfering relation with the chute against the yieldable resistance of a spring.