A self-cleaning mixer includes a cylindrical housing and a feedscrew extending longitudinally through the housing for mixing water and cement and conveying the slurry through the housing. A chute at the infeed end of the housing receives a batch of material and directs the material into the housing. The feedscrew turns on a hollow shaft including a plurality of outwardly directed nozzles along a portion of the length of the shaft. The housing includes a plurality of inwardly directed nozzles fed from a pair of manifolds. During a cleaning cycle, one of the manifolds is shut off, thereby increasing the water pressure in the other manifold and increasing the force of the spray to enhance cleaning. The housing is slightly inclined to provide gravity feed of slurry in addition to the feedscrew.