Concrete Contractors

Concrete Repair – What You Need to Know

Concrete repairs help prevent safety hazards that can lead to tripping and falling. They can also extend the lifespan of concrete structures.

Concrete Repair

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A good repair material will have low shrinkage and be able to bond well to existing concrete. It should be easily workable and not suck water out of the old concrete as it sets.

Cracks in concrete are a common sight and if not addressed properly, can lead to more significant structural problems. Cracks usually form due to drying shrinkage, thermal movement and/or loading. Structural cracks pose a danger to pedestrian safety as they can become a passageway for moisture and destructive environmental substances such as salts, chloride, etc. These can corrode reinforcement steel, weaken the concrete and lead to spalling. Non-structural cracks, however, do not pose a threat to safety and can be fixed using a variety of repair techniques.

The first step in any crack repair is to clean the area thoroughly using a wire brush, broom and clean water. Any loose debris or dirt must be removed because it can keep the filler material from bonding to the concrete. Then, use a sledgehammer and chisel to undercut the sides of the crack, creating a V-shape. This will help the new filler to better adhere to the concrete and reduce the chances of the crack reoccurring in the future.

Next, fill the crack with a concrete repair product of your choice. It is important to follow the manufacturer’s instructions as different products cure differently. If the crack is deep, then it is a good idea to use foam backer rod to create a base for the repair. Backer rod is available in a variety of sizes and can be stuffed into the crack to a depth of about 1/4 inch. Once the crack is filled, you should smooth the surface by “floating” it with a margin trowel and then diverting traffic away from the repair until it cures.

For shallow pits, the approach is similar to that for cracks. First, remove any loose debris and then wash the pit with a clean water stream. If necessary, use a concrete cleaner to ensure that the surface is free of contaminants. Then, if the crack is active, a routing and sealing method may be the best option. If the crack is dormant, a flexible sealant may be sufficient. In either case, it is important to address the underlying issue that caused the crack to appear.

Spalling

Spalling in concrete is one of the most serious issues that can affect the integrity of a concrete structure. It involves a flaking of the surface layer which exposes aggregate and reduces concrete strength. It can also lead to structural deterioration as the weakened concrete is more likely to crack and delaminate. Spalling can impact the safety of occupants and pose trip and fall hazards, so it’s important to address the issue as soon as possible.

There are a number of causes of spalling, including low cover (reinforcement too close to the concrete surface), poor quality concrete, moisture ingress, chemical attack, and poor fixing details. It’s also known as concrete cancer, and although it may initially appear cosmetic it can be a significant threat to the structural stability of your property.

Once spalling has started it can spread rapidly and degrade the entire concrete slab. This is because the first line of defence – the top surface of the concrete – has been removed, leaving the underlying aggregate exposed. The resulting degradation of the concrete is much faster than if the concrete was left intact as it no longer has the protection of the concrete topping.

Repairing spalled concrete is a complex process and should only be undertaken by a qualified concrete professional. It’s important to spray the affected area with water prior to applying any repair materials as this will prevent the new concrete from robbing the existing concrete of its water and causing it to weaken over time.

In some cases, a full-depth repair is required in order to restore the structural integrity of a damaged concrete slab. It’s recommended to use a specialist concrete repair contractor who can assess the damage, recommend the best method of repair and provide appropriate guidance for the project.

It’s also important to choose the right repair products and apply them in accordance with the manufacturer’s recommendations. Different repair methods are used for different types of damage and using the wrong approach can cause further deterioration, increase repair costs and delay your return to normal service.

Expansion Joint Issues

The expansion joints that are found in concrete surfaces like large commercial or apartment buildings, sidewalks and the bridges we use each day serve an important purpose. They are designed to absorb stress from temperature changes, preventing cracks in concrete slabs. However, when these expansion joints are not correctly maintained or resurfaced on a regular basis, they can start to develop issues that affect the entire structure.

One major problem that can occur is water leakage from these areas, which may cause structural damage to the building over time. Since concrete is a porous material, it expands and contracts with weather changes. The expansion joint is meant to let the concrete heave with the soil beneath, but when it fails, it can start to damage the slab itself.

Luckily, these expansion joints are fairly easy to repair. By removing the old expansion joint and cleaning it, a bonding adhesive can be applied followed by the addition of foam backer rod and then a self-leveling urethane sealant. When this is done, the area should be blocked off until it dries.

The other issue that often occurs in these types of joints is wear and tear due to heavy traffic. This is especially true in industrial settings where the floors are regularly impacted by equipment like forklifts. The expansion joints can break down and start to degrade over time, leading to costly impact damage to the floor.

If the concrete is properly inspected and maintained, these expansion joints can last for years to come. When these joints begin to deteriorate, it is important to address them immediately to avoid any future damage to the concrete.

The best way to prevent these issues from happening in the first place is to conduct regular inspections by a professional concrete contractor. The contractors can identify any potential problems with the expansion joints and make any necessary repairs before they cause serious damage to the concrete. This can save you the cost of having to completely rebuild a section of the concrete and it will help prevent any future water damage and cracking.

Epoxy and Urethane Injections

Epoxy crack injections are one of the most popular and cost-effective concrete repair methods for non-moving cracks. When properly installed, epoxy injections effectively seal and bond to sound concrete, restoring the structural integrity of the concrete slab. In addition, they are ideal for stabilizing structures subjected to heavy loads and structural movement.

The first step in performing an epoxy crack injection is to ensure that the crack and surrounding area is clean. Using a wire brush and/or compressed air, debris must be removed from the surface to be repaired. It is also critical that the crack remain dry at the time of injecting, as any water seepage will result in a failure of the epoxy paste-over.

Before injecting, a surface port adhesive, such as Sealboss 4500 crack-sealer, must be applied to the crack surface. Surface ports are then installed along the length of the crack. Using an air gun, hand-actuated delivery system or dual cartridge dispensing system, the injection epoxy is dispensed into the crack. It is important to inject enough material to fill the entire crack width. Too little material will result in a weak, brittle repair. Too much material will cause the crack to enlarge and/or branch off below the surface.

Once injected, the crack must be agitated to help the epoxy flow into and through the crack voids. The epoxy should be allowed to cure for at least 24 hours. During this time, the crack should be agitated every hour to ensure that the injection epoxy is saturating the crack.

After the injection epoxy has cured, any surface seal left on the surface of the concrete can be removed for cosmetic reasons. The injection ports can also be removed if desired.

Both epoxy and urethane foam provide high tensile strengths and are effective in sealing hairline cracks and larger voids in concrete foundations. Epoxy is more dependent on temperature and other weather conditions, however, so it is less suitable for wet crack repair. On the other hand, polyurethane is less sensitive to these variables and is more versatile for use in moist or muddy conditions.