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Mortar Mixer vs Concrete Mixer: Which One Do You Need?
Mortar mixers and concrete mixers both turn bagged material and water into something you can place, but they mix in opposite ways. Use the wrong one and you either fight sticky mortar in a drum that can't fold it, or you strain paddles on coarse gravel. This guide explains how each type works, which jobs suit each, and how to size one, using IMER machines as the examples. Shop the categories in our mortar mixers and concrete mixers collections.
How a concrete mixer works
A concrete (drum) mixer turns the whole drum. Fins inside lift the mix and drop it back on itself, so the stones in the concrete do much of the mixing. That tumbling action suits concrete with coarse aggregate. It is less effective with sticky, sand-only mixes such as mortar, stucco and plaster, which tend to cling to the drum instead of folding.
Drum mixers are rated two ways: drum capacity (the total volume of the drum) and batch output (the mixed volume you get out per load). Batch output is always smaller, so size by batch output.
How a mortar mixer works
A mortar mixer keeps the tub still and turns paddles through the material. The paddles shear and fold sticky mixes evenly, which is why masons, plasterers and stucco crews use them. There are two main designs:
- Horizontal-shaft mixers run a paddle shaft along the length of the tub. They are the standard mason's mixer for mortar, stucco and plaster, and they tip to dump into a wheelbarrow or mortar pan. Example: the IMER HSM 8.
- Vertical-shaft (pan) mixers spin paddles around a vertical shaft in a round pan and discharge through a door in the floor of the pan. They handle stiff, low-water mixes such as dry pack, screed and refractory well. Example: the IMER Mix 120 Plus.
IMER's vertical-shaft mixers list a maximum aggregate size of 3/8 in. For concrete with larger stone, use a drum mixer.
Which one do you need?
| Job | Best fit | Why |
|---|---|---|
| Concrete with gravel: footings, posts, pads, small slabs | Drum concrete mixer | Tumbling action is built for coarse aggregate |
| Brick and block mortar | Horizontal-shaft mortar mixer | Paddles fold sticky mortar evenly |
| Stucco and plaster | Horizontal-shaft mortar mixer | Even, lump-free mix for hand or pump application |
| Dry pack, screed, refractory and stiff mixes | Vertical-shaft pan mixer | Forced mixing handles low-water material |
| Thinset, grout and epoxy by the bucket | Bucket/paddle mixer | Small batches mixed right in the bucket |
| Bagged premixed mortar and plaster at high volume | Continuous mixer | Mixes as you feed bags, with no batching |
IMER mixers compared
| Model | Type | Batch output | Power options | Weight |
|---|---|---|---|---|
| Wheelman II | Drum (portable) | 2.5 cu ft | 1/2 HP, 120V | 101 lb |
| Minuteman II | Drum (portable, tripod stand) | 3 cu ft | 1/2 HP, 120V | 101 lb |
| Multi-Mix 350 | Drum (portable) | 9.5 cu ft | 1.5 HP, 120V | 385 lb |
| Workman II 250 | Drum (towable) | 6 cu ft | Honda GX160 gas or 1.5 HP electric | 525 lb |
| Workman II 350 | Drum (towable) | 9.5 cu ft | Honda GX160 gas or 1.5 HP electric | 650 lb |
| Mix-All 60 | Bucket/paddle | 12 gal (one 50 lb bag) | 3/4 HP, 120V | 66 lb |
| Mix 120 Plus | Vertical shaft | 3 cu ft | 2 HP, 120V | 286 lb |
| HSM 6 | Horizontal shaft (towable) | 6 cu ft (2–2.5 bags) | Honda GX160 gas or 1.5 HP electric | 500 lb |
| HSM 8 | Horizontal shaft (towable) | 8 cu ft (2.5–3 bags) | Honda GX240 gas or 1.5 HP electric | 650 lb |
| HSM 12 | Horizontal shaft (towable) | 12 cu ft (3.5–4 bags) | Honda GX390 gas or 5 HP 240V electric | 1,200 lb |
| Mix 360 Plus | Vertical shaft (towable) | 9 cu ft | Honda GXV390 gas or 5 HP 240V electric | 787–794 lb |
| Mix 750 | Vertical shaft (towable) | 18 cu ft | 5 HP 240V, 7.5 HP 3-phase or Honda 13 HP gas | 1,588 lb |
| Spin Max | Continuous | 3 cu yd/hr | 1.75 HP, 120V | 195 lb |
Specs are from IMER USA's published data.
How to size a mixer
- Match the batch to your crew. A mixer should finish a fresh batch by the time the crew has used the last one. As a rule of thumb, small crews and repair work suit 6–8 cu ft; bigger crews and large stucco or block jobs move up to 12 cu ft or more.
- Count bags, not drum size. Check the batch output and how many bags it takes, such as 2.5–3 bags for the HSM 8.
- Pick the power for the site. Gas runs anywhere. Electric is quieter and has no exhaust, which matters indoors and on noise-restricted sites, but check the voltage: several larger models need 240V or 3-phase.
- Towable or portable. Towable mixers have a 2 in ball hitch (pintle optional on many) and road tires. Portable 120V mixers fit in a van or pickup and roll through a doorway.
Bottom line
Mixing concrete with gravel? Choose a drum mixer such as the Workman II 350. Mixing mortar, stucco or plaster? Choose a horizontal-shaft mortar mixer such as the HSM 8. Mixing stiff dry pack or screed? Choose a vertical-shaft pan mixer such as the Mix 120 Plus. Browse every model in our IMER collection.