Pressure washers can be used to clean concrete floors, but if the surface is in poor condition and has contaminants, you may need surface conditioning machines like floor scrubbers. Use surface conditioning machines like floor sanders and floor grinders to remove any existing coating on the concrete surface, such as paint, varnish or previous patching material. You can also use pressure washers or power wash surfaces with sandblasters that produce a fine sanding effect without noise or dust pollution.