DIY tools

Concrete has one property that makes tool choice unusually consequential: it starts curing the moment water hits it. That turns every pour into a race, and it means the right mixing method is the one that keeps pace with the pour rather than the one with the best specification.

Throughput by method#

Everything in this section starts here.

An 80 lb bag yields about 0.6 cubic feet mixed, so a cubic yard — 27 cubic feet — is roughly 45 bags. Read that against the table and the crossover points fall out on their own: mixing a cubic yard by hand is a five-and-a-half-hour day, and it is the reason so many DIY slabs have cold joints in them.

The number that decides your method#

Work out your volume first, in cubic yards.

Slab: length × width × thickness in feet, divided by 27. Footing: same arithmetic, for each run.

Then:

• Under 0.5 cubic yards (about 22 bags): mix by hand or with a paddle mixer. A machine is not worth setting up and cleaning.
• 0.5 to 1.5 cubic yards (22–68 bags): rent a drum mixer. This is the sweet spot for rental.
• 1.5 to 3 cubic yards: get quotes for both. Ready-mix short-load delivery becomes competitive here and it removes the labour entirely.
• Over 3 cubic yards: order a truck. Mixing three cubic yards from bags is 135 bags and most of a day, and the delivered price is usually lower once you count the bags.

That last point is worth stating plainly because it cuts against buying any machine: for larger pours, ready-mix is normally cheaper than bagged concrete, before you value your own time at all. Bagged mix costs roughly $250 to $300 per cubic yard in materials. Delivery runs $150 to $200 per yard plus a short-load fee.

Our our concrete bag calculator does the volume arithmetic and the bag count, and compares mixing times across methods.

Where a continuous mixer changes the equation#

A drum mixer works in batches — load, mix, wait, dump. A continuous auger mixer takes dry material at one end and delivers wet mix at the other without stopping.

That does two things beyond raw speed. It removes the seam in your work every time you wait for a batch, which matters for anything where a cold joint is a defect. And it holds a constant water ratio across the whole job, which matters most for mortar and stucco, where varying batches show up as visible colour banding in a finished wall.

The trade is cost and utilities. A continuous mixer needs mains water and an outlet; a gas drum mixer needs neither and goes anywhere. our Mud Mixer MMXR-3225 review covers where that trade lands.

What we look at#

Bags per hour, honestly stated — including what the figure becomes when one person is working alone rather than two. Utility requirements, because a machine that needs mains water cannot go where a petrol drum mixer can. Cleaning time and difficulty, which is the maintenance burden that actually determines whether a mixer stays usable. And the break-even against renting, because for most people in this category renting is the correct answer and a review that will not say so is not much use.

Water is the variable that ruins concrete#

Everything else in this section is about speed. This one is about whether the result is any good, and it is the mistake people make most.

The water-cement ratio is the dominant determinant of concrete strength. Not the brand of mix, not the mixing method, not the cure time — the amount of water relative to cement.

Bagged concrete arrives with the cement and aggregate proportioned correctly, so the only variable you control is the water. The instruction on the bag is the correct ratio.

The problem is that the correct ratio is hard work to mix by hand. Over an afternoon with a hoe, water goes in a splash at a time, and nobody notices crossing from 0.45 to 0.60. The slab that results is not obviously wrong — it looks the same, it hardens, it takes traffic — and it cracks in year five instead of year thirty.

This is the strongest argument for a machine that is not about speed at all. A mixer holds the ratio you set because you are not fighting the material to turn it over.

Clean-up is part of the job, not after it#

Every mixing method has a clean-up cost and it is consistently underestimated, because the job feels finished when the last concrete is placed.

Two rules that apply to all of them. Clean immediately — cured concrete does not come off, and the window is about an hour on a warm day. And do not wash concrete slurry into a storm drain; it is alkaline enough to be a genuine pollutant, and in many jurisdictions it is an offence. Rinse onto gravel or into a pit where it can settle out.