How to repair cracks in concrete

Patching It Up: A Quick Guide to Repairing Concrete Cracks

As tough and durable as concrete might be, over time, cracks and fissures might appear in
even the best handyman’s concrete pours. The freeze-thaw effect of even a minuscule
amount of water that seeps into concrete can soon form unsightly, or even dangerous cracks
in driveways, walls, or other concrete structures.
Depending on the severity of the crack in question, fixing it could be anything from a
10-minute easy-as-can-be epoxy-from-a-tube repair job to a much bigger and more involved
process that requires power tools and quite a bit of handiwork.
An important thing to note when faced with a crack in your concrete is that you can’t simply
fill it up with fresh concrete; unless it’s bigger than 1 cubic foot. As it dries, it will pull away
from the side, simply creating a new crack. Assuming that you’re faced with more than a
hairline crack that can be fixed with a tube of resin mortar, you’ll want to follow the following
steps to ensure a long-lasting watertight fix that will prevent more cracks from opening up.

Step 1: Evaluate the crack, then gather and prepare the tools, and area

Check to see if the crack is larger than roughly 1 cubic foot or simply a hairline fracture. Fill
the former with new concrete, and the latter with a tube of epoxy resin. Most concrete
cracks, however, will be somewhere in between these two sizes. In this case, you’ll want to
follow these steps.

Using a chisel, break away any loose or crumbling concrete bits around the crack. If it looks
like it might crack off soon, it’s better to bust it out now. The goal is to have the crack
surrounded by sturdy concrete edges without any nearby hairline cracks that might cause a
piece to come loose. After that, clear the inside of the crack of any loose debris or dust. A
vacuum cleaner can be really useful here.

Next, get yourself the appropriate epoxy resin mortar from a hardware or DIY store. Epoxy
resin mortar sets without drying out, meaning they completely fill in any cracks and keep
them filled as they cure. These products are available with different-sized aggregates for
different crack depths, so we recommend taking a picture of the crack you want to fill and
asking the salesperson for advice. They might recommend large-aggregate (±4mm) for
deeper holes of 150mm, straight epoxy repair mortar for smaller holes, or even a more
pourable version for long, thin cracks.

While you’re there, also grab yourself a gauging or bucket trowel to scoop the mortar into the
crack more easily, and if you require a smooth surface, maybe a finishing trowel. Depending
on how much epoxy resin mortar you need, you could mix it with any old –but clean, dry, and
dust-free– stick or pole, or get a mixer paddle to make the job easier. We’d also recommend rubber gloves as resin-based compounds are pretty aggressive on the skin, and a solvent to
clean your tools or any messes.

Once you have the area clean and dry, and the epoxy resin mortar ready to go, move on to
the next step.

Step 2: Mix the epoxy resin mortar and fill in the cracks.

All epoxy resin mortars will come with very clear instructions on how to mix. Since different
manufacturers create products with different chemical makeups, it’s critically important to
follow the manufacturer’s instructions to the tee to ensure it sets correctly and lasts the way
you want it to. Typically, you can expect it to take anywhere from around 4 to 6 minutes to
properly mix a 20kg tub of epoxy mortar. Smaller amounts will take about the same amount
of time as you always want to ensure that the hardener is thoroughly mixed in with the resin.

Once your mortar is mixed, use your bucket or gauge trowel to fill the crack with mortar. Take
the time to make sure that you’re filling every nook and cranny without leaving gaps or
bubbles between the concrete and the resin mortar. Once you’ve filled the crack and it’s
level with the base concrete, use your finishing trowel to create a smooth finish by sliding it
along the surface of the new resin mortar and the base concrete. Because epoxy resin
mortar doesn’t dry out the way that concrete does, the surface shouldn’t sag or droop as it
cures.

Step 3: Cleaning, protecting, and curing

Once your epoxy resin mortar has cured and set, it will be incredibly difficult to remove any
messes or excess mortar. This is definitely a job to be done while the mortar is still wet. This
can easily be done by picking up the extra mortar with a trowel and then cleaning the area
with some solvent and a rag. Use the same solvent and rag technique to clean your tool.
Avoid getting the resin mortar or solvent on your skin.
After the area is clean, make sure that nobody walks across the still-wet resin mortar. Either
cover the fixed cracks with a bin liner or other plastic sheeting or lay down some cones or
bollards to ensure that it can cure in peace. Depending on the brand or compound that you
used, it could be safe to walk on after anything from 4 to 24 hours.

When to leave it to the pros

Fixing a crack in concrete is definitely the type of DIY task that you could attempt with a
reasonable chance of success; however, there are cases when it might be easier and
cheaper if left to the professionals. Your cracks might run deeper than you thought, they might be in an area with lots of foot traffic and create a trip hazard, or you might not find the
required epoxy resin mortar in the right quantity. In these situations, surface repair experts
like the ones at WeRestoreSurfaces are the specialists to call to have your cracks filled
professionally, promptly, affordably, and permanently.