How to properly mix concrete

Mixing bags of concrete isn’t complicated. You add some water, stir it up and pour it out. But to get the most strength from the concrete, you have to recognise when it has just the right amount of water mixed in.

Too little water and the particles in the mix won’t stick together.

Too much water weakens the concrete.

In this article, we’ll show you what the perfect mix looks like. We’ll also show you a mixing technique that will ensure thoroughly mixed concrete with a minimum of effort. When done well, the concrete should last a lifetime.

Before you begin mixing concrete

For most small jobs around the home, bagged concrete mix is the most convenient and least expensive way to go. You can use it for fence post footings, deck footings and even small concrete pads. For jobs requiring more than about 30 bags, consider ordering “ready-mix” concrete from a truck instead.

Ten or 20 kilogram bags of concrete mix are readily available at home centres  and hardware stores. Don’t confuse concrete mix with sand mix or mortar mix. They don’t contain the aggregate (stones or gravel) that’s necessary to make a pour thicker than about 20mm. You’re likely to find more than one kind of concrete mix on the shelf, but for most jobs, standard concrete mix is fine. Read the recommendations on the bags or check manufacturers’ websites to find out if one of the special mixes would work better for your project.

Whether you hand mix concrete in a plastic tub, homemade mixing tub or wheelbarrow, the technique is the same to find the right concrete mix ratio. However, it’s easier to move and dump concrete that’s mixed in a wheelbarrow. For larger jobs, you could rent a mixer, but it may be more economical to simply order ready-mix concrete. In addition to a mixing container, you’ll need a sturdy hoe and a large bucket as well as a stiff-bristle scrub brush to clean the equipment. Wear waterproof gloves and safety glasses because the cement mixing in the concrete mix is caustic and can burn skin. Wash it off with water if it gets on your skin.

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Slice and dump the bag

Set the bag of concrete mix in one end of the wheelbarrow and slice it open with your hoe. Dump the mix from the bag and pull out the paper bag.

Add a measured amount of water

One of the most common mistakes beginners make is to add too much water and end up with concrete that’s thin and soupy. Here are a few tips to avoid the problem and find the right concrete mix ratio.

First, pour a measured amount of water (amount varies with bag size) into the mix from a bucket rather than squirting it in with a hose. For future reference, mark the water level with a permanent marker. Pour the water into the opposite end of the wheelbarrow, reserving about 4 cups to add later if needed. Continue mixing for a few minutes after all the water is absorbed because the concrete will often get soupier as you mix. If you add more water right away, it may end up runnier than you’d like. Finally, keep at least a few cups of dry concrete mix handy just in case your mix gets too thin.

Gradually wet the concrete mix

Pull a small amount of the dry mix into the water with a hoe and mix it completely. A hoe makes a great mixing tool. A flat shovel or spade works too. Continue pulling and mixing until all of the powder is wetted and the mix is piled at your end of the wheelbarrow. Continue mixing by going to the other end of the wheelbarrow and pulling the mix back toward you. This method ensures that all the dry particles are completely wetted.

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Mixing concrete technique

Use a sturdy wheelbarrow to mix your concrete. And make sure it’s on a level surface. Brace the wheelbarrow with your knee when you’re mixing from the side.

Work it to the perfect concrete mix ratio

If the mixed concrete looks like the mix above, it’s ready to pour. Otherwise, mix in additional dry mix or water until you get the right consistency.

It’s tempting to just squirt water into the dry concrete mix with a hose and mix up a soupy batch of concrete. After all, it’s quicker and the runny concrete is easier to pour. The trouble is, soupy concrete is only about half as strong as a proper mix and is more likely to crack. That’s why we recommend spending a little extra time measuring the water into a bucket first and adding only as much as is needed. Even though the thicker mix is a little harder to place, it’ll be worth the extra effort. We’ll show you how to get the best consistency.

Too dry concrete

Drag the hoe through the mix to make a trough. The mix is too dry if the sides of the trough are crumbly and the concrete falls in chunks when you disturb it. Add water one cup at a time, mixing between each addition.

Too runny concrete

Add more dry concrete if the mix is too wet and soupy and sags into the trench.

Just right concrete mix

The mix is just right when the sides of the trough stand and the ingredients are thoroughly wetted. A hoe patted against the concrete will leave a slightly shiny surface.