Concrete is an inexpensive construction material that has been used for more than two thousand years. Domes, columns, beams, slabs, sidewalks and backyard patios are made of concrete. With proper care and use, concrete construction can last several lifetimes. However, all concrete construction has one problem in common. A flaking, crumbling part of the surface, called a spawl or spall, is an early warning sign that concrete repairs are required. Repair a concrete spawl immediately to minimize the extent and expense of the work. Choose repair materials to match requirements of the installation.
Determine the cause of the spawl. Moisture is the most common problem. Other causes include impact, overloading, exposure to chemicals or too much water in the original concrete mix. Eliminate these problems wherever possible to extend the life of the repair. Test new concrete at the time of placement to confirm that the mix contains the specified amount of water.
Remove the damaged concrete. Establish a perimeter around the damaged area by cutting into the concrete at the depth recommended by the manufacturer of the repair material. Use a saw specifically designed for cutting concrete, such as a Hilti handheld gas saw. .
Use a 30-lb. jackhammer to remove bulk concrete to the recommended depth. Use a 15-lb. jackhammer for finishing corners and edges. Do not cut or damage steel reinforcing. If reinforcing material is located in spawling concrete, undercut it by a minimum of 3/4 of an inch. If the reinforcing material is rusted, continue removing surrounding concrete until exposed reinforcing steel is in good condition.
Clean the exposed surfaces. Sandblast or power wash concrete and reinforcing steel to remove all loose materials, dust particles and rust. Vacuum clean.
Prepare the surface. Saturate the remaining concrete with water before pouring the repair material. Make sure that there is no remaining standing water and that the surface is dry to the touch prior to construction. Install a bond coat consisting of cement and water immediately before pouring repair materials.
Pour repair material and finish per manufacturer's recommendations. Vibrate the repair concrete mechanically or by hand to insure maximum contact with existing concrete and steel reinforcing. Level the repair material to match the existing concrete's grade and slope. Finish with a trowel or broom.
Cure the repair. Apply a chemical curing compound per manufacturer's recommendations or cover the repair with wet burlap and plastic sheeting to control evaporation. Cure for a minimum of seven days to allow a concrete repair to reach maximum strength.