How to Repair Broken Concrete

Tough as it is, concrete doesn't hold up forever, especially if abused. When it does break, it's usually along an edge or at a corner, areas that are exposed to the most impact and wear.

Fortunately, edges are easy to fix, and if you go about the job correctly, your repair should be as strong as the existing concrete. Small repairs: If your repair is fairly small - something like a chipped corner - you won't need to use any forms or any special reinforcement. Start by chipping away all loose concrete. Use a cold chisel, a hammer and an aggressive attitude. Make sure you remove anything loose or flaking, all the way back to solid concrete. You can use a special patching cement if you like, or just mix up a batch of mortar, made of three parts sand and one part portland cement. The smaller the repair, the more sense it makes to use special patching cements. Small repairs made with ordinary cement tend to dry out too quickly and thus lose most of their strength. Special patching mixes contain synthetic additives that largely eliminate this problem. If you use the patching cement, simply follow the directions on the label.

If you mix your own mortar, use just enough water to make a firm paste that will hold its shape. Set this aside for a minute and mix up a creamy slurry of pure portland cement and water. Dampen the exposed surface of the old concrete with water, and then brush on a thin coat of the cement slurry. This will act as a bonding agent and help assure a strong repair. Quickly, before the slurry can dry out, trowel on your mortar, shaping it to match the original corner. Press the mortar down firmly to assure good contact, but don't worry about shaping things perfectly at this point. Let the mortar set from one to five hours - until it retains a firmly pressed thumbprint. Now, use your trowel to do the final shaping. Let the mortar cure for at least a week, keeping it damp the whole time. If the mortar dries out prematurely, it will lose much of its strength. So sprinkle it lightly every hour or so for a few more hours; then, cover with damp rags and keep these soaked for a full week.