How to make concrete

Concrete uses

Concrete is commonly used for building bridges and roads, creating building blocks and slabs, and laying bases for garden sheds, residential buildings, and fence posts.

Concrete comes in various types, each of which has different compositions and strengths. The weight of the load the concrete needs to support and the specific application you need it for can affect the type of concrete you use and the method for making it.

For example, foundations for a high-rise building require durable concrete that can withstand large vertical loads and environmental impact with a minimum compressive strength class of C40/50 (at the high end of the scale). However, most shed bases only need a C20/25 concrete mix, making for a strong yet cost-effective option.

Concrete ratios

Concrete is incredibly flexible, as you can adjust the ratios of the cement, sand, aggregate, and water that makes it up to best suit your project's needs. Changing the mix ratio adjusts the strength, durability, weather resistance, and other properties.

A standard concrete ratio of 1:2:3 means it’s made of one part cement, two parts sand, and three parts aggregate. If you use ballast (a mix of sand and gravel) to mix concrete, you can replace the sand and aggregate with a ratio of 1:4.

These are some of the most common concrete ratios and their uses:

• 1:2:3 – one of the most popular concrete mix ratios used for shed bases, concrete slabs, and residential foundations.
• 1:2:4 – concrete with greater strength used for high-rise building foundations and structural elements.
• 1:2.5:3.5 – a standard strength mix suitable for light wall foundations and bases for fence posts.
• 1:1.5:2.5 – strong concrete ratio ideal for outdoor steps, paving, and driveways exposed to the elements.
• 1:3:6 – a higher volume of aggregate creates concrete with greater wear resistance from weight, rain, and abrasion, best for roads and pavements.
• 1:0.5:1 – an impermeable concrete mix to avoid leaks, often used in water retaining structures such as dams.

Tools for making concrete

Tools required to make concrete will depend on whether you’re doing it by hand or using a mixer:

• Cement mixer (if using a mixer)
• Builders’ bucket (when mixing manually)
• Mixing board
• Spade or shovel
• Plastic bucket (for water)
• Wheelbarrow
• Tarpaulin sheet.

Safety equipment for making concrete

• Safety goggles
• Dust mask or mouth protector
• Thick gloves.

How to make concrete: Step-by-step guide

You can make concrete either manually or with a mixer. If you only need a small amount or don’t have a cement mixer, then follow these steps to make your own concrete by hand.

Prepare the equipment and materials

1. Gather the tools and materials you need and put on the appropriate safety gear.

2. Lay the tarpaulin down close to where you’ll apply the concrete and put the builders’ buckets on it.

Measure the ratio of ingredients

1. Measure the volume of sand, aggregate, and cement for your chosen ratio using buckets of the same size.
2. Pour the dry ingredients and water into these separate buckets placed on the tarpaulin.

Mix the dry ingredients

1. Shovel the sand and aggregate into a large builders’ bucket or onto a mixing board, depending on how much concrete you’re making.
2. Continuously fold over until it’s completely mixed and a consistent colour.
3. Add the cement and fold in until you’ve got an even mix.
4. Form a mound and create a crater in the middle about half the size of its diameter.

Add water slowly

1. Carefully pour a small amount of water into the top of the mound to fill the crater.
2. Using your shovel, fold over the dry material into the water.
3. Keep mixing it until it forms a smooth, consistent paste, adding more water until there are no dry patches, but avoid it getting sloppy.

Check the consistency

1. Create ridges in the mixture with the edge of your shovel and see if they hold to check the consistency.
2. If it’s crumbly and dry, then add a bit more water slowly.
3. If the ridges collapse, it’s too watery, so add more dry ingredients
4. You may need some trial and error initially, so keep mixing until you achieve a good consistency.

Pour and apply the concrete quickly

When you’re happy with the concrete’s consistency, you can use it in your project, whether it’s to set a fence post, create a base for a shed, or to lay a garden path. Don’t wait too long to avoid the concrete hardening before it’s applied.

How to make concrete with a cement mixer

Mistakes to avoid when making concrete

Making concrete may be a relatively straightforward task, but there are some common mistakes to avoid to ensure you don’t impact the strength and quality of your project, including:

• Applying concrete when it’s too hot, which can cause fast drying.
• Making concrete when it’s cold or wet, meaning it may set with weak resistance – especially when temperatures are below 4°C.
• Producing a large amount of concrete in one go, which can cause it to dry out before you have a chance to use it all.
• Pouring in too much water at once and creating a wet mixture that’s weak and causes cracks.
• Failing to measure ingredient volumes carefully, which can lead to a mix that’s not suitable for your project.

Hire a range of quality concrete equipment from Jewson to help your next project run smoothly