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This job sends a lot of dust and concrete debris into the air. Prevent injuries by wearing goggles and a dust mask. Protect your hands with a thick pair of work gloves.  For added comfort, wear knee pads. These will prevent pain and bruising when you kneel down on the concrete. If you don’t have knee pads, you can also lay a padded mat in your work area. The bonding material won’t stick as well to rounded edges. Take a chisel and hammer and tap any rounded edges to straighten them out.  If you make a mistake and chisel off too much, don’t worry. You can patch those holes the same way you’re patching the main crack. Don’t chisel just for the sake of it. If the edges are already squared and straight, then skip this step. Large pieces of concrete and debris will prevent the bonding agent from making a good seal. Remove all large pieces with a broom and scoop them into a pail. Don’t worry if there is dust or smaller debris left behind. This step is only to remove large pieces that a vacuum can’t pick up. Remove any dust and small debris from the crack to help the mortar bond better. Use a shop vac to clean the crack and surrounding area. Pass over the area several times and ensure you’ve picked up all the debris. If you don’t have a shop vac, don’t use a normal vacuum cleaner. Concrete shards could damage it. Instead, use a fine brush to sweep up dust and smaller debris as well as you can. Dip the brush in water and scrub every part of the crack or hole. This gives the bonding material a greater surface area to adhere to. Make sure you get all the edges, sides, and the bottom of the damaged area. Generally, you don't have to wait for the water to evaporate before applying the bonding agent. However, read the instructions on the product you use. If it tells you to apply the agent to dry concrete, then wait for the water to dry.
Put on goggles, gloves, and a dust mask to protect yourself. Chisel the sides of the crack or hole to make them square. Sweep any large concrete chunks out of the hole. Vacuum the area with a shop vac. Scrub the damaged area with a wire brush and water.