Patching concrete drives is not for the faint-hearted. It’s best to start in the knowledge that the patch is never going to blend in seamlessly with the rest of the drive, and that it will always look like a patch. With this in mind, you need to be sure it’s worth doing and be prepared to repair a larger area than you need to help it to blend in.
Complete Concrete Layer Repairs
It is possible to replace the whole depth of the layer of concrete, but it is a job that needs tools like concrete power saws, that the average DIY person is unlikely to possess. It also involves inserting steel dowels or anchor bolts into the side of the existing concrete before pouring the new concrete into the hole.
Bearing in mind the complexity of the job, it is recommended that this is left to the professionals, unless you have a great deal of experience with concrete. This article will cover shallow patching, which can cover flaking or cracking due to frost.
Shallow Patch Repairs
Pick a dry weekend for the job as water getting into the drive and then freezing can cause even more damage. Set out the area, looking at other lines and seams in the concrete to see if you can make the patch match up with existing lines. Once marked out, the edges can be cut with a power saw or grinder with the correct blade, going down about an inch and a half (about 4cm).
Then cut out the inside of the area to the same depth, using a hammer and cold chisel, or go to a hire shop for a special-purpose demolition hammer. It’s vital to remove as much of the small pieces of grit and dust as possible, as any residue will weaken the repair.
Preparing and Pouring
Priming of the exposed concrete will then be necessary. This can be done with acid-etching or, easier for the amateur, a PVA or SBR bonding agent, which can be obtained from a builders’ merchant. Then, using a high-strength mix, make up enough concrete to be poured into the hole.
Spread the concrete out into the hole, pushing it well into the corners and edges. Tamp it out to force air bubbles to the surface and level it with a straight edge across the hole, so that you can make sure that the new patch is level with the existing surface.
If the rest of the drive is textured, you can try producing the same texture over the patch for up to about 5 hours after the patch has been laid, depending on the weather. This needs careful consideration as it may make the patch look worse. As each case is different you will have to decide on the day what will be the best approach.
Drying and Curing the Patch
Keep everyone away from the concrete for the first 24 hours at least, to allow it to begin the curing process. If there is a sudden cold snap before the patch is fully cured, protect it with sacking or old blankets. If it’s too hot, there is a chance the concrete will dry out too quickly and weaken, so cover it with plastic sheets to hold moisture in. Take them off periodically to allow evaporated water trapped by the sheets to run off.
Assuming the patch is in a driveway it is probably alright to allow traffic over it four or five days after the repair has been laid, and full strength will be achieved after about a fortnight.