Filling concrete expansion joints with sand – Is this Legit?


Filling Concrete Expansion Joints with Sand – Is this Legit?

Expansion joints are a huge part of construction because they allow materials to withstand the shrinking and expanding effects of the surrounding temperature. Concrete, the most common construction material, is known to expand during the summer and contract during the winter. The expansion will cause the concrete cement, like your concrete driveways, to expand and crack. With the assistance of the expansion joints, your concrete will expand but not crack. However, there are questions on what materials to be used in filling up these concrete joints, and perhaps sand might do.

Can I fill concrete expansion joints with sand? Yes, you may use sand as a filling material before finishing it off with epoxy coating. The best type of sand to use is silica sand.Silica sand is an excellent extender for epoxy-based compounds and sealants.

In this article, we will go through the prospects of using sand as a filling material for concrete expansion joints. There will also be a brief discussion on the purpose, nature, and composition of concrete expansion joints. Some people do not even know what a concrete expansion joint is and what purpose it serves. 

Importance of Concrete Expansion Joints

Asphalt expands in the summer heat

Nature of Concrete Expansion Joints

When concrete dries after it is used for constructing structures, whether it be walls, driveways, posts,etc., it shrinks and undergoes irreversible structural alterations. Furthermore, throughout its life, the concrete shall further undergo contraction and expansion depending on the surrounding temperature. During the summer when the heat of the sun is at its peak, the concrete will expand. When winter comes, the drop in the temperature causes the concrete to contract and shrink.

Concrete will suffer tension and stress whenever it contracts and expands. This is where concrete expansion joints come into play. The expansion joints relieve the stress and tension on the concrete. 

The joints absorb the temperature induced expansion and contraction while at the same time holding the parts together. You often see concrete expansion joints at home in exterior concrete structures like, driveways or pavements near the house. 

Composition of Concrete Joints

When created, concrete expansion joints will always have a crevice or space between the two concrete structures it holds. This crevice or space is often filled with various materials and subsequently sealed by epoxy or polyurethane sealants. The filling and sealing of the joint are intended to prevent deterioration of the joint, such as erosion and cockroach infestation. 

As for the filling materials, the common materials used for filling include Sponge Rubber, Asphalt, Ceramar Foam, Fiber Expansion, and Granulated Cork. However, the option to use other construction materials as fillers is available. The following sections will go through the prospects, benefits, and drawbacks of using sand as filling material.

Silica Sand As A Filling Material

Of all the types of sand that are used as construction material, silica sand serves as the most viable filling material for concrete expansion joints. While other types of sand, such as concrete sand, masonry sand, and crushed stone sand, also do well as filling materials, silica sand stands as the best filler material. The silica sand qualities make it a viable substitute for the best filling materials, such as the expensive sponge rubber and Ceramar foam. 

Nature and Composition of Silica Sand

Silica sand is also known as quartz sand, white sand, or industrial sand. When compared to regular sand, for example, one that you will find on the beach, silica sand is purer because it is only made up of two elements, silicon, and oxygen. The impurities of regular sand make it highly reactive to other elements, which in turn makes it not durable to withstand weathering and other environmental factors. 

Thus, silica sand, being “pure” and free from other elements, makes it the best sand type to use for construction purposes, especially as filling materials. Silica sand is known to be very durable when used with sealants such as epoxy and polyurethane. Its composition also makes it waterproof, thereby eliminating the risk of having water leakages. Water leakages on expansion joints can hasten the deterioration of the construction.

Qualities of Silica Sand 

Silica sand is known to have a very high melting and boiling point, making it super resistant to the heat of the sun. When used as filling material on exterior expansion joints, the sun’s heat has little to no effect on the silica sand, whether physically or chemically speaking. Although it comes in its fine texture, silica sand is also known for its hardness, which adds to its durability. It has a rating of seven out of ten in the Mohs Scale, the scale that rates the hardness of minerals.

Commercial Silica Sand

Silica sand is commercially available in almost all parts of the world. In 2018, the global demand for silica sand reached 291 million metric tons. That number is a 5% increase from the 2017 global demand for silica sand. It manifests the importance of silica sand in industries such as glass, foundry, and building products sectors. Nowadays, you can readily buy a bag of silica sand on online sites, such as Amazon.

Silica Sand Is A Good Filler For Expansion Joints

Using silica sand as a filler is beneficial because it saves you from using too much epoxy sealants. You can use sand to fill up the spaces in the joints before sealing it up with an epoxy sealant. Silica sand matches well with epoxy sealants.

Silica sand is also a good filler because it is waterproof and weatherproof. Unless a significantly strong force is applied, like one from a strong earthquake, the silica sand filler perfectly holds.  Silica sand also prevents water from leaking inside and causing holes and crevices.

roads have expansion joints built in for heat

Tips In Filling Up Expansion Joints

Check the Weather Forecast Before Filling Up the Expansion Joints

Like most activities involving construction, there is a perfect time to fill up your driveway’s expansion joints. First off, avoid filling up the expansion joint when there is a probable rain coming in within 24 hours. Your sealant will cure for at the very least one day before it becomes totally waterproof.

Since exterior expansion joints, like the one in your driveway, are exposed to the elements, avoid filling up when the temperature goes beyond 38 degrees Celsius. The heat of the sun will cause the joint to expand before you even manage to fill it up with the filler and sealed with the sealant. The perfect ambient temperature to fill up the joint would be around 25 degrees Celsius.

Clean the Expansion Joint First Before Filling it Up

Make sure that the space where you intend to fill up is free from materials such as dirt, stones, and trash. This is to ensure that the space will only be filled up by the filling material and the sealant. Allowing other materials to be included in the mix will lessen the durability of the expansion joint. 

Buy and Prepare the Materials Beforehand

Preparation is crucial in any endeavor, and so it is very important that you have your materials, sealant, filling material, basic hand tools, etc., ready on hand. It would be unwise to start filling the expansion joint without having things prepared. Doing so would often result in shoddy output. Remember that you expect your expansion joint to last for years, so do the job properly.

Seal the Expansion Joint Properly

Seal the joint properly to make sure that no water or anything can pass through and damage it. Water can easily enter if the sealant is not properly and equally applied. Never forget that sealants will often, at the very least, take one day to cure. Before that happens, the sealant is vulnerable to being washed away.

Treatment Of Expansion Joints Enhance Durability

example of a concrete expansion joint

There will come a time when your expansion joints will need treatment. This is normal because no expansion joint, like any other construction, will last forever. The key is to prolong its life expectancy by treatment. This may involve cleaning, resealing, covering, and other modern methods.

Problems That Expansion Joints Face

Your expansion joints are susceptible to three problems, water leakage, cockroach or insect infestation, or initial poor workmanship. Water leakage is problematic because the more water that goes through the joint, the more it becomes damaged. The water leakage will commence a chain of events wherein more and more water will come in and damage the joint.

Cockroach and insect infestation is also a concern. Expansion Joints are often the perfect spot for insects to hide and multiply. The space protects them from the elements of weather, such as rain. Them breeding in the expansion joints is definitely an unwanted occurrence. 

Treatment Methods

Resealing your expansion joints every now and then will ensure that water will not be able to enter it. You will know when your expansion joints need resealing. Once the old sealants have started to crack or show signs of significant deterioration, such as flattening, immediately remove the old layer of sealant. Proceed to reseal it with the same sealant.

Cleaning the surface of the expansion joint is the most basic treatment method you can do to your expansion joint. Remove anything that can deteriorate the surface of the joint, especially the layers of sealant. 

Fibertapes Help Waterproof Your Expansion Joints

Others apply fiber tapes or adhesive tapes over the sealed expansion joint. The fiber tapes or adhesive tapes make the sealant more waterproof because it prohibits water from passing through the joint.  The tape also prolongs the life of the sealant because it serves as the first layer of shield.


Filling up your expansion joints with sand, especially silica sand, is not a bad idea. Silica sand has properties and qualities that make it a viable alternative to other filling materials. It is way cheaper when compared to your other options, such as rubber sponge and asphalt. Regardless, know that expansion joints are very important because they allow your concrete cement to expand and contract without damaging itself. You cannot avoid the expansion and contraction of concrete, but you can prevent it from damaging itself, by a properly made expansion joint.

Answering this question is closely related to our section on home garages. I highly recommend checking it out. There’s a bunch of interesting articles in there that you might find useful Garage Section Of Houshia


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Steve Foster

Suburbanite, tech geek, handy man, automation enthusiast who started blogging about the stuff I do around my home and found he had a knack for it.

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