There are two main types of concrete mixers: batch mixers that mix concrete in batches that must be fully emptied and cleaned between batches, and continuous mixers that continuously produce concrete. Batch mixers can be horizontal drum mixers or vertical pan mixers. Drum mixers have fixed blades inside a rotating drum while pan mixers have either a rotating pan or blades. Continuous mixers are non-tilting drums with rotating screw-type blades that continuously feed and discharge concrete.