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About This Project
If your concrete driveway and steps look like a scene from a vintage World War II movie, it’s time to strap on your dust mask, arm yourself with a chisel and a trowel and fight back. Don’t let that broken corner, hairline crack or crumbling surface defeat you. A repair done properly will extend the life of your concrete if you catch the trouble early enough. This article will show you how to create a durable concrete patch to fix two of the most common problems: spalling and broken corners.
We won’t deal with the other common problem, cracks. You can repair them exactly as we show here, but they’ll most likely return unless you can stabilize the concrete slab to prevent the movement that caused the cracks in the first place.
Concrete Repair is For Everyone
Concrete is hard stuff, but don’t let that intimidate you. With the proper tools and techniques, even a novice can make a durable patch, first try. Sawing concrete with a special masonry blade may be new to you, but if you’ve handled a circular saw, you’ll quickly get the hang of it. It’s less hazardous than sawing wood. However, the blade kicks up an incredibly thick cloud of abrasive dust, so be sure to wear goggles to protect your eyes, ear protection, gloves and a dust mask, as well as old clothes.
TIP: You’ll raise an impressive dust cloud when sawing, so close up nearby windows and doors. Otherwise, you’ll be housecleaning, too!
Size Up the Job First
Before beginning any repair, assess the general condition of the concrete slab. (See “Patch or Replace?”) Sometimes
the best strategy is to break out an entire section and repour it with new concrete rather than patch it. Patching works best for local damage in otherwise sound concrete.
If this is your first concrete repair project, allow about a half day to pick up materials and complete two to three patches. It took us about four hours from start to finish to complete the two repairs we show here.
Complete the job during comfortable working conditions, ideally in dry weather with a temperature between 50 and 80 degrees F. Both you and fresh concrete happen to agree on this one. Fresh concrete is easiest to handle and hardens best (a process technically called “setting” and “curing”) in this temperature range. Colder weather lengthens the setting time; freezing temperatures can ruin the concrete. Hotter weather causes faster setting and drying; the slab may harden before you can smooth it. Or the surface can dry too fast and not harden properly, eventually causing it to spall. In hot weather, work in the cooler mornings or in the shade.
TIP: Spend $20 to repair the damage yourself or pay a pro $300 to $400 to replace this simple slab.
To Repair Spalled Areas
The key to a lasting repair is to make a saw cut around the perimeter of the damaged area, cutting back to solid concrete. The cut
should be at least 3/8 in. deep: Most repairs that fail do so because the patch is too thin at the edges and breaks off. Set a masonry blade (see below) at a 5-degree angle so the cutout is slightly wider at the bottom than at the top. This helps “lock in” the patch. Slowly guide the saw through the concrete. The masonry blade grinds a groove, so don’t put a lot of pressure on the saw; let the blade do the work. Cut about 1/4 in. on each pass.
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