Concrete Pavement Repair
Concrete Pavement Repair is usually made with Portland cement concrete. The repair material should match the mix design chart specified on the project’s materials schedule.
Longitudinal patch perimeter joints should be prepared with a bond breaker for stable repair. The bond breaker should rest against the existing slab on both repair sides.
Repairing Cracks
Concrete is prone to cracking, especially in areas that are heavily used. These cracks need to be repaired in order to prevent them from becoming worse. Otherwise they may be gulped with water in the freeze/thaw cycle, which can cause them to expand and cause even more damage.
Control joints are placed in the slab to help control where cracks might form. Sometimes these cracks can extend beyond the control joints, which is why it’s important to fill them properly. This can be done with epoxy or polyurethane concrete crack filler, or a caulking product that’s designed to be non-sag and long lasting.
Before applying the concrete patching compound, make sure that all cracks are cleaned out, and that any loose material is removed. This will ensure that the new material sticks well to the concrete surface and helps prevent it from coming loose in the future. This will also help to prolong the lifespan of your concrete pavement.
Then you can apply the repair product, which is usually an epoxy or latex type. After applying the product, use a plastic putty knife to spread it and to force it down into the crack. Then smooth it level with the surrounding concrete surface, if necessary. This will create a smooth surface, and prevent the crack from reopening when traffic is applied to it. Different products require different curing times, so check the instructions for the specific product that you are using.
It’s always a good idea to apply a sealant over the repaired crack, and this can be done with a water-based acrylic product, a solvent-based asphalt emulsion, or a polyurethane sealant. This will help to keep moisture and other damaging materials out of the cracked area, and prolong its lifespan. When the sealant is dry, it can be buffed with 60 grit sandpaper, to smooth it and make sure that it blends into the concrete surface. This step is crucial, and can make the difference between a repaired crack that lasts for years, and one that reopens within weeks or months.
Sealing Cracks
Concrete crack repair requires the proper materials and method to prevent further damage. Choosing the right materials for the job will depend on the size and type of crack, as well as any other factors that may be causing problems, such as water penetration or shifts in ground level. The first step in repairing cracks is cleaning the area thoroughly. Using a pressure washer or blower to clear out dirt, dust, and debris will ensure that the repair material sticks properly. If the crack is deep, a backer rod can be stuffed into it to fill up space, allowing you to use less of your chosen crack repair product and create a stronger bond.
Hairline cracks are very small, thin cracks that appear on the surface of concrete surfaces over time. These can be caused by natural shrinkage during drying or by minor temperature changes, and while they might seem insignificant, sealing them early can prevent them from growing into bigger issues. For these cracks, simple caulking or concrete crack filler should work fine.
Narrow cracks are a little wider than hairline cracks but still remain under 1/4 inch wide. These can also be caused by shifts in the ground underneath or from changes in the concrete slab itself. For these cracks, a vinyl concrete patching compound can be used to fill the gap and smooth the surface.
Longitudinal cracks are deeper than either of these types of cracks and tend to run the length of the paving structure. These cracks can weaken the underlying layers of the pavement and lead to serious structural problems if not addressed. For longitudinal cracks, hot-pour or cold-pour sealants can be applied to stop moisture infiltration and halt further deterioration.
Before applying any kind of crack sealant, a layer of bonding adhesive should be applied to the surface of the concrete. This will allow the new patching compound to adhere to the concrete, preventing it from lifting or flaking in the future. This can be applied with a caulk tube, bottle, or pre-mixed product from a bucket. Once the patching product is applied to the concrete, it should be textured to match the surrounding concrete and left to dry according to the manufacturer’s instructions.
Repairing Faults
Concrete pavements are prone to cracking under certain conditions, but proper design and construction, as well as routine maintenance, can minimize unsightly and structural cracks. For example, addressing small cracks promptly with a rubberized or polyurethane sealant can extend the life of concrete and reduce the need for costly full-depth repairs later.
Other common problems include spalling, scaling, settlement, and discoloration. Generally, a light bituminous seal over these areas is sufficient to maintain the life of the concrete. Spalling and scaling are signs of deterioration that can lead to structural damage, such as delaminations, which may require full-depth repair. Discoloration is often caused by iron pyrites or other contaminates, but also may be due to poor concrete construction, curing methods, or weather effects. Settlement is a result of shifts or compression in the soil beneath the concrete that can cause deformation and loss of strength.
Faults in the joints are a serious problem because they can compromise the structural integrity of the entire pavement. They can occur because of poor construction, overloading, or environmental stress, and accelerated by freeze-thaw cycles. Joints that are not properly repaired can deteriorate quickly and become more severe over time, resulting in safety hazards for pedestrians and vehicles.
When a fault occurs, the contractor must determine the extent of the damage. This is done by conducting a sounding test. A sounding tool is used to probe the depth of the damage to the concrete surface or subbase and to expose a core for evaluation.
A saw cut is then made around the perimeter of the repair area to provide a vertical face at the edges of the repair and a good bond with the concrete surface that will be restored with the patching material. The damaged concrete within the saw cut is broken out using light pneumatic tools until sound and clean concrete is exposed along the bottom of the repair area as shown in Figure 10-10.
The repair area is cleaned of all loose material to improve the bond between the existing pavement and the patching mixture. A neat, blended epoxy primer shall be applied to the concrete surface before placing the patching mixture. It is important to keep the primer in place after the placement of the mixture until traffic is allowed on the repair area.
Repairing Joints
A well-designed, constructed, and maintained concrete pavement can last many decades. However, even the best quality concrete will eventually need to be repaired. Small repairs made before they become large, expensive problems save time and money in the long run. A routine preventative maintenance program is the best way to get the most out of any existing concrete pavement.
Preparing the Repair Area
Evaluating a concrete surface and determining what needs to be done is the first step in any concrete repair project. Clearing the area of debris and dirt is also important, as this provides a clean surface for the new material to bond to. Finally, ensuring the area is free of water is vital. Any standing water will affect the hydration of the newly placed repair material and may result in premature failure.
For concrete pavement repairs, a good starting point is to remove any spalling and localized delaminations with a saw cut. This will help to prevent the spread of the deterioration and will allow the new material to bond with the old concrete.
The next step is to prepare the longitudinal joints at the patch perimeter. Depending on the specifications, this may require drilling and anchoring tie bars or wiggle bolts to keep the patch in contact with the existing concrete lane or shoulder. Longitudinal joint preparation is also critical in repair areas that abut working joints or cracks. If the work zone is close to a joint or crack, a compressible insert medium should be used to maintain these working joints and cracks.
Lastly, the new concrete should be placed and compacted in accordance with the specification. Often this requires the use of a vibratory screed and a 3-m (10-ft) straightedge to ensure a consistent surface profile. In addition, the finish and texture of the patch should be similar to the surrounding surface.
While it’s always a good idea to make repairs when they are needed, it’s equally important not to repair the wrong thing. For example, if a concrete pavement has been spalling and there is evidence of D-cracking in the vicinity of the spalling, Class A partial depth repairs are usually not appropriate and full slab replacement should be considered instead. Likewise, it is usually not necessary to repair joints or cracks that have faulted but are still stable. These types of repairs can create more problems than they solve by creating 2 joints where there was one before and adding to the stress on the concrete surface.
