Abstract: An apparatus for treating horizontal surfaces with abrasive particles. The apparatus utilizes a housing with flat, straight walls in a rebound chamber and a return corridor. Removable wearplates are attached to the inside walls of the rebound chamber to prevent wear on the rebound chamber walls. Abrasive particles are gravity-fed from a hopper to a blast drum having blades for propelling the abrasive particles to the surface to be treated. The abrasive particles rebound from the surface into the rebound chamber. The flat walls of the rebound chamber are arranged to divert the abrasive particles into the lower end of the return corridor with minimal wall contact. At the lower end of the return corridor the air flow from a dust collector takes over to draw the abrasive particles into a collection chamber. The abrasive particles pass through perforations in the wall of the collection chamber and into the hopper for reuse.