The Difference Between Concrete and Screed
Concrete and screed are similar in some respects. They are both made from the same basic materials: cement, water and aggregate (sand, stone or gravel). But, when it comes to their uses as building materials, concrete and screed are very different. Quality concrete is used for construction and structural tasks, while screed is applied as a top layer to a concrete base.
Physical differences between concrete and screed
Concrete and screed are both made from a mixture of cement, water and aggregate. The main difference between the two materials is the type of aggregate that is used.
When we are mixing concrete, we add coarse aggregate like gravel to the mix. These small stones are normally 20mm or less in size. This coarse aggregate gives the concrete its strength, durability and workability, and makes it suitable for structural work.
For screed, we don’t use the gravelly aggregate that we put in our concrete. Instead, we use fine, sharp sand, with a maximum grain size of about 4mm. This is what gives screed its fine, tightly packed texture and makes it suitable for applying as a top layer to a concrete floor.
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Do concrete and screed look different?
Concrete has a rougher texture than screed because it contains coarse aggregates. You’ll be able to see bits of gravel and stone in the mix. Screed is more like mortar and has a more fine-grained look. It is rough but very fine, like hard-packed wet sand that has dried solid.
Concrete is normally laid much thicker than screed, with a recommended thickness of at least 100mm for domestic use, and up to double that thickness for areas in which there is heavy use. Screed is commonly about 50–100mm thick (on average, about 75mm).
What are concrete and screed used for?
Concrete is an ideal building material because it has the potential to reach a very high compressive strength. Other qualities are that it’s durable, economical, long-lasting and non-combustible. It’s also highly versatile and, as long as it’s quality-assured, is safe to use in everything from large-scale structural works to small home renovation projects.
We often deliver readymix concrete for:
- Drainage layers
- Car parks
Screed is not used in structural works but rather as a top layer for a concrete floor. It’s durable and designed to withstand the impact of constant use and heavy footfall. This protects the concrete floor to make it last longer, and gives it an even, level finish. It is also highly insulating, which is why it is often used for floors with underfloor heating systems.
We provide our customers with screed for:
- Concrete floors
- Underfloor heating systems
How are concrete and screed made?
We use volumetric mixers to produce all our concretes and screeds. Our team loads up the mixer’s separated hoppers with separated high-end aggregates – using coarse aggregate for concrete and fine aggregate for screed. We are able to precisely control the ratios of raw materials being mixed, which is how we create different types of concrete and screed. The concrete or screed is mixed fresh onsite and barrowed or pumped to where you need it.
Concrete and screed mix designs can both be altered to meet your requirements. We can adjust the ratios or introduce admixtures to give the material different qualities. If you need a lightweight concrete or screed, for example, an aggregate like LYTAG could be used in the mix. Or, for a higher compressive strength, we can adjust the water-cement ratio as needed.
The benefits of concrete and screed
Concrete has the potential to hit a very high compressive strength, which makes it an ideal building material. It is used in everything from walls, driveways, patios and roads to piling, concrete floors and other building structures. As well as being immensely strong, concrete is durable, economical, long-lasting and versatile. It is also non-combustible, which means that it could be advantageous in the event of a fire. The main benefit of readymix concrete, in particular, is that it can be batched to your exact specifications and amount using volumetric mixers.
Screed is generally used to create a smooth, bump-free finish to a concrete floor or surface. As well as improving a concrete base aesthetically, it can also lengthen its life – the compact mix of sharp sand and cement provides a durable and long-lasting top layer that protects the concrete floor from the impact of constant use and heavy footfall.
Admixtures for concrete and screed
We can introduce admixtures to both concretes and screeds to alter their properties. We might add plasticisers to enhance the workability of the material, or to enhance bonding, reduce shrinkage or increase its damp-proofing capabilities. Sometimes, we use admixtures to slow down or speed up the setting time. For our screed products, we often add fibres to reduce cracking, and retarders to make the material stay workable for longer.
How do you know if concrete and screed are high quality?
For both materials, you should look for BSI certification. This shows that the supplier meets strict quality standards. We highly recommend choosing a quality-assured concrete supplier over a cheaper option. Premium suppliers like Rapid Readymix use separate virgin aggregate rather than recycled ballast mix, which gives us full control over the quality of your material.
Order concrete or screed today
If you’re ready to place an order for concrete or screed, or want to talk to our team further about the differences between the two materials, contact us at Rapid Readymix today.