Those grey-looking sealants between sections of concrete are actually something called expansion heave protection to foundations material. It's what gives the concrete a chance to bend without breaking.

Expansion joints should extend the full depth and width of a concrete slab to allow for expansion and contraction. They should be spaced approx 30 times the thickness of the slab – for example a 5m x 5m slab would have joints spaced every 3 metres.
FORMING THE JOINT

As concrete dries and sets, it shrinks and expands as the temperature changes around it. Some parts of the concrete shrink more than others, pulling and stressing those areas causing cracks to form. This is why concrete slabs must be constructed with a variety of joints, so that the whole slab can move without straining or causing cracks to randomly appear in the cement.

When forming these joints, it is important to space them correctly and use the proper material to protect the concrete. Expansion joints are typically made from an elastomeric rubber or fiber-infused foam, both of which can be purchased at most home improvement stores.

In addition to preventing concrete from cracking, these joint materials provide extra structural support for the slab by providing additional reinforcement. They also make it easier to install and maintain the concrete.

The type of joint you use will depend on several factors, including where it is placed and how much movement the slab needs to withstand. In general, the expansion joint should be placed between the slab and anything else that could cause the concrete to shift.

If the expansion joint is placed in an area with a lot of movement, it should be made from an elastomeric foam. This type of joint is a great choice for commercial, residential and industrial projects.

It is easy to install and has the added benefit of being able to be cut with a saw. It is also a great option for smaller jobs as it is relatively inexpensive to buy and will last a long time.

Another option is a rubber or foam expansion joint which is poured directly into the concrete as it dries. This method is more expensive but it can be a good choice for commercial projects as it can be installed quicker than a traditional concrete expansion joint.

The elastomeric or fiber-infused foam can be molded into the concrete as it dries and will be able to absorb the expansion and contraction that the concrete experiences during its lifespan. It also provides a better seal than a traditional expansion joint and will be less prone to leakage when it is cured.
NAILING THE FORM

It may be a little more work than the standard lumber form, but it's the best way to create an expansion joint that won't come crashing down. The most important thing is to choose the right material for your application and make sure it withstands the elements, including water.

You'll need a few tools to get the job done, but it doesn't have to break the bank. A hammer drill is ideal for this job, but you can also use an electric or manual drill. If you're using a drill with a variable speed trigger, try not to exceed its maximum power setting as this can cause the bit to overheat.

One of the most difficult parts is finding the right board. We recommend choosing a hardwood such as pine or cedar that's been properly treated with stain and finish to minimize moisture damage. Once you've chosen your wood, cut it to the correct dimensions and mark a line down the middle of the board. If you're not using a measuring tape, a good rule of thumb is to leave about 2 inches of overhang at the edges for future bracing and nailing.

There are many other types of construction forms on the market, so be sure to read the manufacturer's specifications carefully before deciding which one to use. The best ones should last a long time. They can be used for a variety of projects, from driveways to sidewalks and patios.
NEXT STEP

The right concrete expansion joint can reduce stress, enhance the performance of a concrete slab and prolong the life of your home. An expansion joint is a little bit of clever engineering. Its job is to provide a small space for the concrete to expand or contract without damaging surrounding structures.

Expansion joints are often the icing on the cake when it comes to improving the performance of concrete slabs, walls and other structural components. They can be found at a variety of locations, including but not limited to: footpaths connecting to a driveway; the junction section of a footpath or the joining of a floor slab to a staircase or column; a building or kerb and any other structure that is joined by a concrete slab.

It's a good idea to get the best quality product that will stand up to your particular application. That means a sealant that withstands the rigors of time, sun and rain, preferably one with some moisture resistance as well.

It's no secret that concrete expands and contracts with the changing temperature of the earth's surface, but the right concrete expansion joint can help minimize the damage. The most important thing is to install the correct type of expansion joint and make sure it's a tight fit.
FINISHING THE JOINT

Concrete needs to be finished properly to make it look great and function well. This includes a smooth, flat surface that does not have sharp corners and a joint pattern that is attractive to the end-user of the concrete.

Finishing also helps reduce water logging, which is the process of evaporation after the concrete dries. This makes the concrete more breathable and easier to clean.

FINISHING the concrete is a vital part of concrete construction, but it is also a job that can be dangerous if done improperly. It is important to do the work right so that you can enjoy the finished product for many years to come.

The finishing of concrete is a complex process that requires specific equipment and expertise to complete successfully. There are a number of different types of joint filler materials available for use on concrete, so it is important to choose the correct material for the application you are working on.

Foam expansion joints can be a good choice when you need a flexible joint filler. This type of joint filler will not stain and is very durable. It is also lightweight and easy to work with.

Fibre expansion joints are another type of joint filler that is commonly used. These joints are made from a combination of cellulose long strand fibres and asphaltic binder, which allows the joint to expand up to 140% of its original thickness after installation, thus reducing the stress on the concrete as it is exposed to moisture and temperature changes.

Expansion joints are needed wherever a slab of concrete meets another piece of concrete, a building, or an object such as a pool coping. They should extend the length of the slab and allow movement, minimizing cracking in the concrete.

When these joints are not closed or sealed they can become an area that dries out quickly and gets clogged with dirt, debris, and weeds. The weeds and dirt will degrade the joint filler material and cause it to delaminate, erode, and sag.

Whenever possible, seal the joints with a high-quality urethane caulk (Vulkem #116) to prevent rain from entering the joint and freezing. This will help prevent voids from developing under the slab that can cause major cracking during freezing winter conditions.