Eugene is a trained engineer and self-taught home improvement enthusiast with almost 40 years of professional and DIY experience.
Make Concrete Without a Mixer
A cement mixer does a great job at mixing concrete, thoroughly blending the materials to give a consistent result. However it's also possible to mix concrete by hand without a mixer with a little care and some effort. Sometimes the need arises to mix concrete for setting gate, fence posts or a clothes line into the ground. Another possibility is that you have to make a concrete slab to act as a base for something like a fuel bunker. All you need for mixing concrete are cement, stone, sand and water. Minimal tools are required: A shovel, a couple of buckets and optionally a sheet of plastic.
This is the first of a two part guide. My other guide shows you how to use a cement mixer for making concrete:
How Do I Mix Concrete? - 8 Easy Steps!
- Spread a plastic sheet on the ground.
- Measure out the materials.
- Place the stone and sand into a pile on the sheet.
- Place the cement on top of the pile of sand and stone.
- Shovel the material in the pile to one side, creating a new pile and repeat three times.
- Make a deep crater in the pile and add water.
- Fold the mix in from the sides.
- Continue to fold inwards and "chop" the pile to distribute water through the mix.
See below for lots more details and photos.
What is Cement?
Cement is a binder, used as an ingredient in combination with sand and stone (types of aggregate) to make a composite material called concrete. The three constituents on their own have no real strength but when bound together, stones interlock like a 3D jigsaw puzzle and sand and cement fills the gaps. Cement just glues the stones and sand together and without it, the latter would just slump and fall apart, but it's the stone that gives concrete its shear and compressive strength, not the cement.
There are several different types of cement, two examples are Portland cement and blast furnace slag cement. Portland cement is made by baking limestone in kilns and grinding the clinker produced with a little gypsum to form a fine powder. Blast furnace slag cement is made from the waste products of the steel industry.
Your Options - Pre-mix Concrete or Make Your Own
If you need to mix concrete by hand, there are two options:
- Buy a bag of pre-mixed concrete (drymix). This is available at all good home improvement stores. It has all the ingredients dry mixed together for making concrete, i.e. the cement, sand and stone. All you have to do is put it into a bucket, wheelbarrow or on a piece of plastic on the ground, add water and spend a few minutes mixing it. Usually the product comes in 2 to 4 stone bags ( 10 kg to 25 kg) with varied setting times. Quick setting concrete is available for fixing posts into the ground so that they don't have to be stayed.
- Mix your own concrete from sand, cement and stone. Premixed products from stores tend to work out much more expensive if you're going to need several wheelbarrows of concrete. The alternative is to mix your own. Ideally stone should be 30 mm (3/4"). Instead of sand and stone you can use ballast (mixed aggregate or "all in") which is a mixture containing varying sizes of particles ranging from sand to larger stones. Ballast can have a varying proportion of sand/stone, so you may need to judge whether you have to add additional sand.
Crushed stone is produced in quarries by crushing blasted rock and then the result is graded by being passed through a succession of sieves. In theory, this should make better concrete than rounded stone from gravel pits, because of the sharp angular edges.
Materials Required and Concrete Mixing Ratios
A C20 mix consists of:
- 1 part cement
- 2 parts sand
- 4 parts stone
Read More From Dengarden
Alternatively, instead of sand and stone, a mix called ballast, mixed aggregate or "all in" can be used, and this is mixed 6 to 1 with the cement.
A stronger, more hard wearing C30 mix, suitable for thinner and narrower concrete slabs, e.g. pavements, consists of:
- 1 part cement
- 2 parts sand
- 3 parts stone
As in the case of the C20 mix, if you're using ballast (sand and stone), mix it 5 to 1 with the cement.
Ideally stone should be crushed and 15 to 20 mm in size (9/16 to 13/16 inches).
Sharp sand should be used, graded from 0 to 5mm. Don't use fine stuff which is really for mortar/plastering.
Cement is generally available in 25kg bags. In the US it is sold in 47 or 94 pound bags
How Much Water For Making Concrete?
The amount of water needed to make concrete falls within a range of 0.4 to 0.5 times the weight of cement. So if we take a mid range figure of 0.5, then for a 25 kg bag of cement:
25 x 0.5 = 12.5 kg of water or 12.5 litres
This is 90% of the the volume of a 3 UK gallon (Imperial) bucket. Since the aggregate may be wet, this can mean that less water is actually needed, so these values are approximate.
The mix shouldn't be sloppy and should be able to self support itself without slumping. Concrete that is too dry is unworkable. Sloppy concrete due to excess water will be weak.
What Does C20 Mix Concrete Mean?
It means the concrete can withstand a compressive force (or more correctly pressure) of 20 newtons per square millimetre (20 MPa) without crushing. So in theory, for a 10 cm x 10 cm square (about 4 inches x 4 inches):
Area = 100mm x 100mm = 10,000 square millimetres
So total compressive force that the concrete can withstand without crushing is:
Force = pressure x area = 20 N/mm2 x 10,000 mm2 = 200,000 newtons.
A newton is equivalent to a weight of about 0.1 kg so:
200,000 newtons = 200,000 x 0.1 = 20,000 kg weight or 20 metric tonnes on a 10 cm by 10 cm square.
In reality a concrete slab would probably crack or sink with much less than this magnitude of load. This is because the underside of the slab would be spanning the individual stones of the sub base foundation and not supported underneath at every point over its full extent. These figures really refer to the compressive strength of a 150 mm concrete cube, cured for 28 days as measured on a test jig.
Tools and Equipment For Mixing Concrete
- Builders shovel. (The pointy type one)
- Ideally three, 3 gallon buckets. One for water, one for cement and one for sand/stone. If the sand or stone is wet and you use this bucket afterwards for measuring cement, it will stick to the sides and bottom.
- Polythene sheeting. A sheet of polythene helps to prevent mess and contamination of the concrete by pebbles, leaves, soil and other debris. It also makes it easier to scrape up all the leftovers with no wastage. I use 1200 gauge polythene (the heavy stuff used as a damp proof membrane under concrete) and this is widely available in hardware stores. You can of course mix concrete in a wheel barrow or bucket, but there's more room to mix on a sheet.
- Wheelbarrow or buckets. For transporting the concrete to its final destination. Alternatively you can mix in situ.
For laying concrete, you can use a garden rake or a 1 x 4 board nailed or screwed onto a length of 1 1/2 x 2 for spreading.
Do I Need to Wear Personal Protective Equipment (PPE) When Mixing Concrete?
- A dust mask will help to prevent the inhalation of fine cement dust while measuring out.
- Gloves to protect hands. Cement is somewhat caustic when dry, so if you have sensitive hands, these will give protection.
- Safety glasses stop cement dust or splashes of concrete from getting into your eyes
- Steel toe-capped boots. Optional. You may end up standing in or close to concrete while mixing/laying. Steel toe-caps protect your toes from dropped bricks, blocks or rocks. They normally also have a steel insole to protect feet from nails, glass or other objects that penetrate the outer sole.
Mixing Concrete: Sand, Cement, Gravel, and Water
When mixing by hand, it is essential to thoroughly mix the concrete to get consistency throughout the mixture.
If you need to mix a small amount, for instance half a bucket, place the stone and sand and finally the cement into the bucket. This needs to be thoroughly dry mixed with a garden or block layers trowel. Water is then added, say half a pint at a time and mixed throughout the bucket. More water can be added until the concrete is at the required consistency. If the mixture becomes too sloppy, add more cement. If you are filling a hole in the ground e.g. around a post, the mixture can be a bit more sloppy so that it flows easier.
Larger quantities of concrete can be mixed on a flat surface on the ground
You can measure the proportions of the mix by counting shovels. However I find it easier to use buckets. If you go for a C20 mix, a single mix using buckets ( which totals 7 buckets of material) is enough to produce a wheelbarrow of concrete.
So remember you need:
- 1 bucket of cement
- 2 buckets of sand
- 4 buckets of stone
- If you're using polythene sheet, spread it on the ground and weigh it down with blocks/bricks or whatever at the edges in windy weather
- Place the stone onto the ground followed by the sand. Alternatively you may have gravel which is a composite mix of large and small stone and sand. If there isn't much sand in the gravel, you can add some more
- Place the cement evenly onto the top of the pile. If you have someone to help you mix, it will be easier. Start at the edge of the pile with the other person facing you. The aim is for both people to keep shovelling the pile to one side to create a new pile adjacent to the old pile. Repeat this three times so that's four mixes in total.
- Now it's time to add the water. Make a crater in the top of the pile about half its diameter so that it looks like a volcano. Again, it's important that the pile doesn't have slopes that are too steep so when you add the water it breaks through the crater and runs down the slope! Add half the water, the amount depends on the amount of dry mix you have created.
- Now with the shovel, go around the edges of the crater and keep sliding the mix into the center. Then use a chopping motion with the edge of the shovel to mix the water with the dry mixture. Continue to shovel the dry mixture from the edges of the pile towards the center. Eventually the mixture will become easier to control as the water becomes more distributed. Then keep sliding the shovel under the mixture and turn it over bit by bit and use a chopping motion with the edge of the shovel to thoroughly mix the concrete.
- Continue adding water until the concrete is of a consistency that doesn't slump and can support itself in a pile.
Don't forget to wash your shovel when finished before the concrete sets on it!
Should Concrete be Sloppy or Stiff?
Ideally concrete should be able to stand up in a pile on a shovel and not slump. The link in the reference section of this guide explains the details of slump tests.
Step 1: Spread a Plastic Sheet on the Ground
Step 2: Measure Out the Materials
Step 3: Place the Stone and Sand on the Sheet
Step 4: Place the Cement on Top of the Sand and Stone
Step 5: Shovel to One Side From the Edge of the Pile and Repeat Three Times
Step 6: Make a Deep Crater and Add Water
Step 7: Fold the Mix in From the Sides
Step 8: Continue to Fold Inwards and "Chop" the Pile to Distribute Water Through the Mix
- Use timber boards placed at strategic points to act as ramps and bridges so that you can get your wheelbarrow over uneven terrain and ground at different levels
- Don't try to push a loaded wheelbarrow up a step, it's easier to pull it
- Spread concrete with shovels and a rake after you tip it out of the barrow. You can also make up a makeshift rake using a long length of timber with a board nailed to the end
- If you use a cement mixer, obviously you can empty the concrete directly at the point where you need it, rather than transferring to a wheelbarrow
- When laying concrete floor sections adjacent to each other, feather the edge of the new concrete with a sweeping brush so that it blends with the previously laid section
Laying a Concrete Slab
- If you're laying a concrete slab, tip the mix from the barrow within the formwork (the boards which bound the slab) and furthest from the front. Roughly scrape out the barrow and use a rake to spread the concrete, making sure its pushed into all corners. Use the back of the rake with the handle vertical to compact and pack the concrete, especially around the edges of the formwork.
- Start a new mix
- Continue to build up the level of concrete until it's about 1/2" above the formwork boards.
- If you work fast and alone, you should be able to lay about 3 barrow loads of concrete before a slab needs to be screeded (roughly levelled flush with the forms with a timber board)