If you’re working indoors, ventilate the area as much as possible to deal with the dust. Open nearby doors and windows. Turn on any available ventilation fans and vacuum up dust when you’re done. Since concrete can produce a lot of dust, consider protecting nearby areas with a plastic tarp.
If the hole is already greater than 1 in (2. 5 cm) deep, don’t try to make it deeper. Instead, clean it out and choose an appropriate patching compound. If possible, make the bottom part of the hole slightly wider than the top part. You can do this by holding the chisel diagonally to chip away at the bottom edges of the hole. Making the bottom part a little bigger helps lock the patch into the existing concrete. You could also use a circular saw with a masonry bit to cut out damaged concrete. [4] X Research source
Eliminate all debris so it doesn’t get in the way of the patching material. Anything left in the hole will weaken the patch!
Commercial concrete cleaners are very useful for preparing concrete. They eliminate tough stains, dirt, or debris that can weaken the new patch. Debris affects the concrete’s consistency, so the patching material may not bond properly or be as strong as it should be. If the concrete hole looks clean, you can just spray it with water.
Any water left over will weaken the concrete patch as much as loose debris would. Give it plenty of time to dry!
Remember to widen the hole by removing loose concrete first. Most of the time, this will allow you to brush or vacuum out the debris. Keep washing out the hole until you’re sure it looks clean. Watch for the water to stay clear without any debris in it. Then, soak up as much water as possible and let the hole air dry.
A 60 lb (27 kg) bag fills a hole about 1 ft (0. 30 m) long, 3 ft (0. 91 m) wide, and 2 in (5. 1 cm) deep. Unless you’re doing many repairs, a single bag will most likely be enough. If you’re attempting to make your own mortar, combine 1 part Portland cement, 3 parts masonry sand or gravel, and water.
Note that the bonding agent can often be added after you have poured the concrete into the hole. Check the manufacturer’s instructions for more information. You may also be able to mix the bonding agent in with the concrete. This is usually done by replacing 50% to 80% of the water with the bonding agent. If you don’t apply the bonding agent now, lightly dampen the concrete with a moist sponge. Make sure there isn’t any standing water in the hole.
Err on the side of caution when mixing the mortar. You can always add more water, but you can’t remove it. The only way to deal with a runny mix is to add more mortar. Remember to check the manufacturer’s recommendations on how much water to add. Factor in the liquid bonding agent if you plan on adding any to the mix. Make sure you’re wearing safety glasses, a ventilated mask, long jeans, and gloves when mixing mortar. [12] X Expert Source Gerber Ortiz-VegaMasonry Specialist & Founder, GO Masonry LLC Expert Interview. 10 March 2020.
Make adjustments to get the mortar to the proper consistency. Add water gradually to thin it out, mixing it for a minute after each addition to check its consistency again.
Layering mortar is only really useful if you’re working with a deep hole, such as one more than 1 in (2. 5 cm) deep. If you’re fixing a shallow hole, you might as well finish it in one go. Keep the patching material roughly level with the surrounding concrete. Adding more than you need is okay. You will have a chance to eliminate the excess before it dries. Patching a vertical surface, such as a wall, is pretty much the same as patching a hole on the ground. Push the mortar deep into the hole at first, then add more layer by layer. It will stay in place.
The board will collect excess mortar so you can smooth out the patch and keep it level with the surrounding concrete. For vertical surfaces, try dragging a board down over the hole and then going back over the patch with a trowel. If you can’t use a board, just use a trowel or float instead.
Make sure the patch is level with the concrete around it. Use a wood board to remove any excess before smoothing the mortar out and letting it harden.
Keep other people away from the concrete until it has had a chance to cure. Don’t let anyone walk or drive over it, for instance.
The drying time can vary depending on the weather and product used, so check the manufacturer’s recommendations before misting.
Some products may require you to keep the patch covered for up to 28 days while misting each day. Even though this may seem like a long time, it is worth doing if the manufacturer recommends it. Once the concrete has finished curing, remove the plastic sheet and test it out. It should be level with the surrounding concrete and feel hard to the touch.
