Concrete is a highly durable material that has a long history of being used in driveways. However, the concrete can develop unsightly cracks that can spread over time. Fixing cracks before they spread is crucial to maintaining the aesthetics of your driveway.
You can fix cracks in a concrete driveway by first assessing them then cleaning the concrete and leveling the slabs if needed. After chiseling out the crack, apply a sealant and feather it or fill it using concrete. Finally, use stain, resurface, or score the concrete for cosmetic purposes.
Read on to find out exactly how to DIY-fix cracks in your concrete driveway, no matter how big or small.
1. Determine the Cause of Cracking
It’s important to remember that cracking is usually a symptom of other problems.
So, before you begin to navigate how to repair the cracks in your driveway, you need to figure out why it is cracking.
Below are the most common causes of cracking in concrete driveways.
It’s just as important to address the issue as it is to fix your driveway, or else the problem will persist.
Concrete slabs used in driveways are generally stronger than patio concrete, but different concrete mixes can withstand different weights.
If you own a truck or heavier vehicles, the pressure they exert on the concrete will cause it to crack more easily.
Most contractors tend to overshoot their estimations in this regard to stay on the safe side.
Extreme Temperature Fluctuations
Concrete shrinks and expands with temperature fluctuation, and extreme changes in temperature and humidity can cause cracks to form fairly quickly.
This is especially noticeable if the wrong proportion of water and cement is used when mixing the concrete.
To avoid this problem, it’s best to follow the manufacturer’s instructions when mixing cement.
If you have large trees (such as maples, oaks, or even sycamore) near your driveway, their roots can grow very large, spread laterally, and apply pressure from under the concrete.
After some time, the concrete cracks at the surface to relieve some of that pressure.
Fixing the crack in your driveway in this case is only a temporary solution, and you should consult a landscaping professional to find a solution regarding your tree.
Poor Installation or Bad Concrete Mix
You might notice cracking in your driveways if the concrete slabs were not level when laid, or if the concrete mix was too watery.
Bad concrete mix is too wet and will shrink considerably more as the water evaporates and the concrete sets.
As I’ve mentioned earlier, follow the instructions on the concrete packaging for the best results.
Sharp objects and blunt force can also damage concrete.
For example, if you use power tools or chop firewood around your driveway, you can easily damage the surface accidentally.
You can refrain from using really sharp objects around your driveway, but it’s understandable if that’s an unrealistic expectation.
2. Determine the Type and Size of Cracks
Once you’ve determined the cause of cracks in your driveway and taken steps to avoid further damage, you will need to examine the cracking carefully.
Repairing minor cracks is not the same process as fixing a major gaping hole in your driveway.
Generally, you can use sealant to fix cracks that are smaller than a quarter inch (0.6 cm).
Larger cracks require additional measures and might even require mixing concrete.
Of course, if the cracking is widespread, you may consider hiring a professional because the project might be time-consuming and difficult.
If the cracks have developed due to a bad concrete mix, it may be more feasible to redo the entire driveway.
Otherwise, you can always reinforce the existing concrete to withstand harsh weather conditions or excess weight.
3. Clean the Concrete
The next step is to thoroughly clean your driveway, focusing on the concrete.
This means removing any debris in and around the driveway and then power washing it.
Not only will this make it easier to proceed, but regularly cleaning concrete driveways helps prevent cracking in general.
Before power washing, use a regular broom to brush away any powdery debris.
After washing your driveway, I highly recommend waiting for the concrete to dry before you proceed to the next step.
4. Level the Concrete Slabs
If the slabs aren’t at the same level, your driveway will need to be leveled to fix existing cracks and prevent further cracking.
This is a process used to lift sunken concrete slabs by injecting material into the space underneath.
You shouldn’t try leveling if the concrete is all at the same level.
I recommend concrete leveling if you have water issues.
There are two main methods used: mud jacking and poly leveling.
One of the main advantages of concrete leveling is that it’s more cost-effective than slab replacement.
However, if your concrete slab is cracked into pieces smaller than 1 foot by 1 foot (around 0.1 square meters), I suggest replacing the slab for more strength.
Otherwise, here are the two main ways you can bring your concrete slabs to the same level.
In a method that resembles lifting a vehicle using a car jack, mud jacking involves pumping the layer under the concrete slab with a muddy mixture.
This mixture is typically made of cement, sand, and water.
It is injected through pre-drilled holes in the concrete slabs.
While this method is fairly easy for a DIYer and it’s cost-effective, it isn’t as durable and takes up to two days to cure.
I also wouldn’t recommend mud jacking if your driveway is heavily damaged.
This is another injection-based method that can be used to raise the level of your concrete slabs.
It’s also known as slab jacking.
Instead of the cement mixture used in mud jacking, poly leveling uses polyurethane foam.
It is injected into the pre-drilled holes in the same way, and the foam expands to level the slab.
While this method is considerably more durable and requires no heavy equipment, it is much more expensive.
Still, as a DIY project, it’s worth a try. Note that if you try this method, the finished concrete slab will show different colored patches where the foam was injected.
5. Chisel Out the Crack
Once you’re sure the concrete in your driveway is level, you can prepare the crack for the next step.
Before you can fill the crack with suitable material, I highly suggest that you try to chisel it so that the finished driveway is more structurally sound.
Here’s how to chisel out the crack to prepare it for sealant or concrete application:
- Use a concrete chisel for this process. Make sure you aren’t using a cold chisel or a masonry chisel. The right tool will help you get the job done faster and without complications. You will also need a sledgehammer.
- Hold the handle firmly in your hand and align the length of the chisel blade to the side of the crack at a backward angle (45° works well). Ensure that the bevel and the concrete surface are parallel to each other.
- Strike the head of your chisel using a sledgehammer with reasonable force. Continue striking to carve around the crack, working your way along the length of the crack.
Once you’ve chiseled out the crack, use a wire brush to clear away the dust and debris that has collected around the gap.
6. Apply Concrete Sealant
For smaller cracks, a concrete sealant will be sufficient to restore the structural integrity of your driveway.
However, before applying the sealant, you should use a bonding adhesive to prepare the repair area.
A bonding adhesive or bonding agent is a material that is used to help bond old and new concrete layers to each other.
Without it, concrete surfaces must be scored, which is a significantly more laborious task.
The bonding agent will prevent the sealant from coming away from the existing concrete by fusing the materials.
To apply the bonding adhesive, you will need a regular paintbrush.
Dip it in the adhesive, and apply a thin layer in and around the crack to get all the crevices.
Next, fill the crack using the concrete sealant.
Be generous, and make sure there aren’t any air pockets by pushing down on the sealant and using extra material.
Smooth out the area before moving on to the next step.
7. Feather the Sealant
Once the concrete sealant (also known as crack filler) is applied, you can use a trowel to feather the material.
This will ensure that the sealant and existing concrete are level with each other and will make the final results look more even.
Don’t skip this step, because feathering will seriously affect the visual aspect of your driveway repair.
Simply run the trowel towards the edges of the applied sealant, applying moderate pressure.
Repeat until you are satisfied with how it looks.
8. Use Concrete To Fill Larger Cracks
Concrete sealant won’t be enough to fill cracks that are larger than a quarter of an inch (0.6 cm).
In that case, you should use concrete instead.
Keep in mind that this will require mixing concrete, which many DIYers aren’t comfortable handling.
Here’s what to do:
- Add a structural element: You can either install a backer rod or add sand to the large crack in your driveway to add structural support. This will also reduce the amount of concrete filler you’ll need to use.
- Mix concrete: Check the instructions on the packaging of your concrete mix and follow them. You can mix concrete by hand in a bucket, but for larger projects, I would recommend using a drill with a mixing accessory attached. Make sure to add water slowly to avoid watering it down.
- Pour concrete into the crack: Once you have the right consistency, pour the concrete mix into the crack over the backer rod or sand that you’ve filled the crack with.
- Smooth the concrete: Use a trowel to smooth over the concrete and feather it so that it is level with the surrounding (dry) concrete.
- Wait for the curing process: Concrete can take up to two days to dry, and it’s crucial that you don’t use the driveway at all while the concrete is setting. Even walking over the repaired concrete will result in permanent indentations.
9. Hide the Repairs Cosmetically
Once you’ve fixed the cracks in your driveway, you’re going to quickly notice the stark difference between the old concrete and the new (or the sealant). Needless to say, it isn’t aesthetically appealing.
There are three main methods that you can hide your repairs:
I prefer this method because the penetrative stain will give your entire driveway the same color.
However, it is a more laborious process because you will need to stain the whole driveway instead of treating the repaired area only.
This is a method that I would recommend for older driveways with many small cracks all around them.
You can hire a contractor to add score marks on the repaired area to match the older concrete area.
The result may not look brand new, but it’s uniform.
The best solution is to pour a thin layer of concrete all over your entire driveway.
Not only will this method fix the cosmetic problem of having different colored concrete in your driveway, but it will also add a layer of strength to the driveway.
It’s also easy to DIY because all you need to do is pour a watered-down concrete mix on your driveway and spread it using the appropriate tool.
However, you’ll need to wait for the concrete to cure.
Fixing cracks in your concrete driveway is a simple enough project for most people to take on.
All you need is the patience to chisel it out, and the time to wait for the new sealant or concrete to set.
Although you can avoid putting too much weight on your driveway to prolong its lifespan, all concrete slabs eventually crack.
So, learning how to fix it is the best solution.