Clean the post around the area that is being repaired. Use a small amount of water on a sponge or rag and wipe away any residue or debris that is in or around the area. Let the post dry completely. If the crack or hole has water in it, the epoxy and Sakrete will not adhere properly.
Activate the epoxy putty and fill the hole, crack or damaged corner with it. Press as much epoxy as possible into the area. If the post has a decorative square base and has damage try to form the epoxy to the shape of the square. Use the towel to smooth the epoxy out and press the epoxy inward to fill the crack. Let the Epoxy set for at least two hours.
Mix a small amount of Sakrete and water. All brands of ready-mix concrete are different, so read the bag for proportions of water to concrete mix. Cover the area where the epoxy was placed with a layer of concrete. Smooth it out as much as possible to get an even coat.
Wrap the area with the plastic sheeting and tape. Let the repair dry for five days. Sprinkle the repair with water every day and replace the plastic. The plastic will help to cure the concrete and keep it from cracking. Remove the plastic after five days.
Remove the plastic sheeting and inspect the post. Sand any areas that are rough or do not look flush with the post. Remove any dust left from the sandpaper with a dry paint brush.
Apply an even coat of concrete sealant to the entire post with a paint brush. Do not apply large amounts of sealants at one time, to avoid runs or drips. Most sealants dry within 30 minutes and are clear coats. The sealant will protect the post against water damage and prevent cracks.