What Is A Concrete Expansion Joint?
Concrete is one of the most robust and durable building materials in the world, and it is for this reason that it has become so popular and widely used throughout the construction industry.
An ideal choice for a whole host of domestic and commercial applications, if you’re using concrete as part of your next project it’s important to understand how to maximise its use and ensure its properties are effective.
While not always required, a concrete expansion joint is a tool that is sometimes used during the construction process. But what is a concrete expansion joint?
In this article, the team here at Concrete Supply UK will take a look at exactly that, explaining how it works and the benefits of using one.
Read on to find out more.
What is a concrete expansion joint?
A concrete expansion joint is a tool that is used to create a gap in concrete that allows it the space to properly contract and expand as the temperature changes. The expansion joint in concrete forms a break that comes between the concrete you are using and adjoining parts of a structure and it is here where movement can be controlled and allowed without creating undue stress or pressure on the mix.
Without the inclusion of a joint, when the temperature changes the concrete may not have enough space to breathe causing it to crack or become damaged in other ways that undermine the concrete’s integrity and strength.
In short, a concrete expansion joint will help to maintain the structural integrity of the mix, and it also helps to absorb vibrations and sustain soil movement. This could be as a result of heavy traffic or environmental changes like earthquakes.
Common projects where a concrete expansion joint may be used include:
- Buildings
- Bridges
- Pavements
- Driveways
- Foundations
- Piping systems
- And more
Different types of expansion joints
Due to the versatility of construction projects, there is a wide range of concrete expansion joints to choose from. Some use multiple materials at once (metal, rubber, fabric and more) whereas some are made in different variations.
Usually, different ones are used for bridges, masonry, railway projects, piping and ducted air systems as these are the main types of construction projects where they are deemed to be necessary.
However, the full list of types of concrete expansion joints is extensive and includes:
- Single expansion joints
- Hinged expansion joints
- Rectangular expansion joints
- Universal expansion joints
- Thick wall expansion joints
- In-line pressure balanced expansion joints
- Externally pressurised expansion joints
- Elbow pressure balanced expansion joints
- Toroidal expansion joints
- Slip-type expansion joints
- Refractory lined expansion joints
- Gimbal expansion joints
Why are concrete expansion joints needed?
As mentioned above, the primary use of concrete expansion joints is to prevent cracking and damage from occurring on your concrete.
As concrete dries, it is normal for it to shrink slightly. And once it has properly set, it will also expand or contract depending on the temperature and environmental conditions. Concrete expansion joints can then be installed to allow for better movement and stop damage from happening. This is specifically the case when laying slabs where the surface area is greater than 6m2.
They’re also important to consider when consecutive concrete pours have occurred and if concrete is being poured in an area that is bordered by walls or other buildings, or if manholes are also incorporated.
How to install concrete expansion joints
If you need to install an expansion joint in concrete for your next project, the process is fairly straightforward if you follow the correct guidance.
Expansion joints can usually be installed before or after the concrete has been poured. If you want to do it first, then a flexible material will be inserted along the length of the joint before the pouring commences.
Alternatively, if you want to add the joint after pouring, you will need to cut grooves into the concrete that will outline where the joint is going to go.
Follow the tips below for the most effective way to install concrete expansion joints:
- You need to place joints about 30 times the slab thickness apart. This means that if you’re working with a slab that is 100mm thick, the joint needs to be 3,000mm (or three metres) apart.
- Secondly, it’s important that the joints are cut deep enough to be effective. They must be about a quarter of the slab’s thickness. For example, a 100mm slab will need a joint that is 25mm deep.
- If you’ve decided to install expansion joints after the concrete has been poured, it’s important not to wait too long. Wait no more than 12 hours to do so as the concrete may crack if you wait any longer than this.
- Many people decide to place the expansion joints under walls, as this way they will not be visible and therefore do not impact on the aesthetics of the space.
- Finally, bear in mind that expansion joints are most effective when the aspect ratio of the slab is kept at 1:1. However, if you’re working with a 5m X 5m slab, and it is narrower than it is long then you can consider increasing this ratio to 1:5. If you’re unsure on the best place to install expansion joints, you should always get professional help.
At Concrete Supply UK, we’re experts in all things concrete and this includes concrete expansion joints. Our friendly and knowledgeable team are always on hand to advise on what is best for your next project, so feel free to contact us today to discuss your needs.
Furthermore, if you are looking for a completely bespoke concrete mix, we’re here to help. We always formulate quality concrete mixes based on the specific and unique requirements of our clients, and we’ll take the time to get to know you and your needs before supplying and delivering a product that is most suitable. Plus, to keep delay and disruption at a minimum, we only ever deliver quantities that you need.
