Moist the concrete hole, apply a thin layer of cement mortar on the contact surface around the hole and fill the hole with low slump mortar or concrete. The mortar or concrete should be dry enough to be self-standing. A quick set type of cement (hydraulic cement) is recommended.
First, the gap is cleaned of any debris. Then, if the gap is large enough, a backer rod is added to support the caulk. If the gap is smaller, a backer rod is unnecessary and can be filled only using a polymer caulk.
I'd recommend scrubbing any debris from the hole with a wire brush. Once the hole is spotless, you can use Earl's 1kg Concremate Expanding Cement. Only fill the hole so it is flush with the surrounding surface, as this will minimise the amount of sanding required to get a smooth result.
Cracks can be repaired with cement patching material, while corrosion holes require something more substantial, like epoxy putty or steel mesh reinforcement.
A type of sand-cement slurry (called “mud” in the industry) can be used to fill voids under concrete slabs. This mixture of sand, cement, and water is pumped through holes drilled in a slab foundation to fill voids underneath.
Generally, silicone is most effective for small to medium-sized gaps, typically ranging from ⅛ inches to ½ inches. Attempting to seal large gaps with a single application may result in collapse or shrinkage. When facing wider gaps, epoxy-based sealants or specialized gap-filling products may be a better choice.
Caulk, sealants, expanding foam, backer rod, grout, and mortar are among the most commonly used substances for this purpose, offering versatility and durability in different contexts. When selecting the appropriate material for filling a particular gap, several factors must be taken into account.
Powder filler is often for deeper cracks or holes. It's usually cheaper than other fillers, and you mix it yourself. Because of the depths it can fill, it's versatile and can often be used indoors or outdoors. Ready-mixed fillers can be used on a variety of different jobs and are often really easy to apply.
Using a putty knife, spread a thin layer of concrete patching material into the hole. TIP: To create an even surface, always smooth out (feather) the patching material 1"-2" beyond the repaired area. Using a wet sponge, blend the repaired area into the existing surface. Allow the area to dry.
Make sure to use concrete products that are compatible with a liquid bonding agent. Products like Sakrete Sand Mix and Sakrete Fast Set Cement Patcher will work well with a liquid chemical bonding agent such as Sakrete Bonder & Fortifier.
You can pour concrete directly into the hole surrounding the post.
Expandable foam caulk is a better choice for sealing larger gaps and holes. Use it to insulate areas around pipes and electrical outlets and between window jambs.
It could be ½”, ¾”, 1”, etc.
Once the backer rod is set in place, you can then caulk the gap as you normally would.
Caulks should mainly be used for filling small gaps where you need a tight seal. Silicone sealant retains its elasticity even after sealing, making it perfect for use in parts of the home with varying temperatures, like the bathroom.
Concrete caulk sealants are a quick and inexpensive solution to many cracks, gaps and other minor concrete and masonry surface damage. Patios, sidewalks and garage floors are all subject to cracks because concrete is very hard but won't flex. It's important to fill these cracks with a sealer for many reasons.
You want to clean cracks, at least one quarter to 1/2″ deep. With cracks that or more than a 1/4 deep. You can fill with silica sand, play sand, or backer rod.
Secure Set Spray Foam can be used to easily fill both visible and hidden voids. Once filled, the concrete slab is fully supported and the potential for future erosion has be reduced to almost zero.
Slurry is a mixture of cement paste, pigment, and water. It is used to fill in the small air bubbles in the surface of the concrete. This is especially important in something like a concrete countertop, because bacteria can get into those holes and grow.
Polyjacking, also called “foam leveling,” “poly leveling,” or “foam injection leveling,” is a newer form of concrete leveling that uses a liquid foam injected through small holes drilled in a settled slab. Once the foam is injected under the slab, it undergoes a chemical reaction that causes it to expand.