Abstract: A centrifuge for dewatering a fluent aggregate material such as sand. Sand slurry is conducted into a rotating cylindrical drum which has a perforated lateral wall against which a screen is placed. The drum is oriented with the axis disposed vertically. When the centrifuge operates, centrifugal action slings slurry poured into the drum outwardly. Upon contacting the lateral wall, the slurry builds up. When a certain quantity of the slurry has built up at the bottom or floor of the cylinder, additional material cannot resist migrating upwardly. Thickness of the trapped layer varies, being greater at the floor, near the source of the incoming slurry. This trapped layer forms a bed having an inclined wall. Thickness of the bed at the top of the cylinder is determined by a circumferential, inwardly projecting flange or dam located at the top of the cylindrical drum. The sand bed protects metal parts of the centrifuge from abrasion, and also enables water to diffuse therethrough.