It is not uncommon for a concrete wall in your basement or garage to sustain a hairline crack. This type of crack is not severe damage; if handled right away, the crack will not overly affect the integrity of your concrete wall. However, you will need to employ the right strategies for repairing the hairline crack for the best results.
Clear loose debris from inside and around the hairline crack using a wire brush. Then use a vacuum cleaner hose extension to be sure you've removed all debris and dust particles.
Measure the entire length of the hairline crack and mark about every twelve inches with 3-inch finishing nails. Hammer the nails into the crack about 1 inch.
Prepare your crack sealer. Use two-part epoxy crack sealer, and thoroughly mix equal parts of each of the two parts of the sealer using a putty knife.
Brush a small amount of epoxy crack sealer onto the back side of an injection port flange, then place the flange over the top nail and against the wall. Press firmly to secure. Repeat this process for as many nails as you hammered into the hairline crack.
Use the putty knife to fill in the hairline crack on your concrete wall. Push the sealer into the crack and spread it at least 2 inches wide. Make sure you cover the bottom potion of the flange. Let it dry for a few hours or overnight.
Fill a caulking gun with liquid epoxy. Place the nozzle over the bottom flange and push the epoxy into the now covered hairline crack. Continue this process over each flange until you cannot put in any more liquid epoxy.
Push a plastic plug into the flange that you used to inject the epoxy. This will seal it off. After about five days, cut off the protruding elements, including the flange and plug, with a hacksaw.