C20 Concrete Grade Guide

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C20 / Gen 3 / ST1 Concrete Grade Guide

C20 concrete, also know as Gen 3 and ST1 – is one of the most widely used grades of concrete. To learn about more grades of concrete, see our concrete strengths and grades page.

It commonly features in domestic and construction projects.

This is because C20 is known as a medium-strength mix, achieving a compressive strength of 20 Newtons per square millimetre (20N/mm²) after 28 days.

Below, our concrete experts have shared their guide to C20 concrete. Keep reading to find out more about the key properties of C20 concrete, and its most common use cases, and the benefits it offers.

What is C20 concrete?

C20 concrete is concrete that has a compressive strength of 20N/mm² at 28 days (when fully cured). This is denoted by the ‘20’ in its name.

It is also commonly known as Gen 3 concrete (General Concrete Grade 3) and ST1 concrete (Standardised Prescribed Concrete, Type 1).

It is a widely used medium-strength mix, which is suitable for a wide range of domestic and commercial construction projects. In addition to its medium level of strength, it is durable, versatile and affordable (compared to higher strength varieties).

What is C20 concrete used for?

C20 concrete is often used for light-duty construction projects, particularly domestic construction projects.

It can offer a supportive, strong and durable base, but is an affordable choice when the project doesn’t demand a high structural load capacity.

As a result, examples of its use cases include:

• Domestic foundations and footings (e.g. for structures such as outbuildings, sheds and walls)
• Non-reinforced floors for garages
• Non-reinforced floors for houses
• Patios
• Pathways
• Driveways
• Drainage and trench fills
• Unreinforced slab bases (e.g. for greenhouses and small extensions)
• Kerb bedding

Key Benefits of C20 Concrete

• Strength – C20 concrete has more than enough strength to offer for the majority of domestic and light-use projects. Correctly laid and with the right reinforcement, C20 concrete can withstand regular human traffic and light vehicles.
• Durability – C20 concrete is extremely durable, and has a long lifespan, even with minimal maintenance.
• Workability – As a medium-strength concrete variety, C20 concrete can easily be poured and levelled, making it easy to work with.
• Versatility – Its combination of ease of use and medium-level strength makes C20 concrete a great, versatile solution for a wide range of projects and use cases.
• Affordability – C20 concrete achieves the perfect balance between strength and affordability. This is because it possesses enough strength for most use cases but – because it doesn’t have a high ratio of cement, like stronger grades such as C30 or C40 – it is a more affordable solution for projects that don’t require such high levels of strength.

↑ We test all our concrete batches at our our state-of-the-art batching plant in Essex. 

Points to Consider when using C20 Concrete

Although C20 concrete is known for its versatility and can be used in a wide range of different tasks, it isn’t suitable for all project types.

If any of the following conditions apply, then you will need to consider choosing a different concrete type:

• If heavier structural loads are needed – E.g. for a multi-storey building, or when creating reinforced structural elements. In these instances, a higher-grade concrete will be needed.
• If the ground conditions are extreme – E.g. if the ground consists of a high sulphate soil, or will be subject to regular frost. In these conditions, a specialist may recommend that you choose a mixture with additional protection, or a specialist concrete mixture.

C20 Concrete from iMix Concrete

iMix Concrete are one of the UK’s leading ready mixed concrete suppliers.

We supply a wide range of premium quality concrete. This includes C20 concrete, and any other concrete grades, types and volumes that your project may require.

With our own fleet of state-of-the-art delivery vehicles, we deliver concrete directly to sites across London, Kent, Essex and the rest of the UK. What’s more, we will commit to a rapid next day – or even same day – delivery for your order.

So, to find out more about C20 concrete and its uses, or to enlist our specialists to support your project, contact our team today.