Concrete is an extremely durable material, but even it can become damaged over time. Contractors need to know how to identify and solve common problems such as hairline cracks, crazing, discoloration and settlement.
Cracks that are more than 0.25 inches wide are considered structural cracks and need to be addressed as soon as possible. They can lead to more costly repairs and replacements if left untreated. For expert assessment and repair services, contact professionals specializing in concrete Franklin TN.
1. Cracks
Cracks are a concrete-construction annoyance that can take on different forms and affect concrete strength and appearance. From hairline to broad and widespread, a cracked surface can be unsightly and pose tripping hazards. It’s important for concrete contractors to inspect cracks to assess the severity and underlying causes. When addressing cracks, they look for two things: are the cracks “working?” (i.e., spreading), and what caused them in the first place. Cracks that are not active and have been stable for a while can be repaired with routing, filling, or epoxy injection. In general, cracks that are actively growing or spreading require more extensive repair, including removing and replacing the failed concrete.
Structural cracks affect the stability and integrity of a structure, and are more serious than other types of cracks. They can be caused by excessive loads, improper construction practices, foundation settlement, or temperature changes. These cracks are more likely to widen, requiring immediate attention.
Non-structural cracks include plastic shrinkage cracks, crazing, and shear cracking. These cracks are usually cosmetic, and are less of a concern for commercial projects than structural cracks.
Heaving cracks occur when the ground beneath a concrete slab shifts or swells. This is a common problem in regions with extreme weather conditions, and can cause damage to walls or foundations. Preventing heaving cracks is best done through proper drainage, soil compaction, and installation techniques.
Spalling occurs when the outer layers of a concrete slab break down, exposing the underlying material to moisture penetration. It’s often a sign of improper mix, water retention issues, or poor curing conditions. Preventing spalling requires regular inspections, as well as maintaining a good base grade and ensuring that concrete is not being placed in saturated soil.
2. Scaling
Scaling, or local flaking or peeling of the near-surface layer of concrete or mortar, is a common problem that increases maintenance and repair costs for commercial construction. This is caused by repeated freeze-thaw cycles or by exposure to deicing salts and other chemicals that attack hydration of the concrete. The resulting surface material can be soft, porous, and prone to disintegration.
This issue can occur at the surface or in the interior of the concrete slab. To prevent scaling in the concrete, it is critical to have a well-prepared mix design and proper placement, curing, finishing, and protection practices.
Using an air-entraining concrete mix design helps to reduce the susceptibility of concrete to scaling, as does selecting the right aggregates. Proper water-to-cement ratios, adequate consolidation, and consistent placement of the concrete are also important. Including a bleed water barrier and avoiding over-troweling during finishing help to keep the surface layer strong.
If the issue is due to settling or sinking slabs, raising them with concrete leveling can address puddling problems and redirect water away from the areas that pool. If water pooling is caused by the way the concrete was originally poured and finished, it may be possible to fill in low spots with a self-leveling concrete compound or concrete patch.
Another potential cause of scaling is poor curing practices, which can result in insufficient hydration of the surface layer. Adopting good curing methods helps maintain moisture levels, preventing rapid drying that can lead to surface damage and a weak surface. Use of breathable concrete sealers like SpecRez and Cure & Seal 25 can further improve concrete performance by protecting it from moisture and deicing salts.
3. Efflorescence
Concrete is a great building material for a wide variety of applications including driveways, sidewalks, parking lots and more. However, just like many other building materials it isn’t without its flaws. Some of these problems can be caused by improper installation or weather conditions while others simply result from wear and tear. Understanding these common concrete construction issues and the practical solutions to help fix them will ensure a long-lasting, high-quality finish.
Efflorescence is a crystalline deposit of salts that form on the surface of porous materials such as brick, concrete, stucco and stone. These soluble salts are drawn upward by capillary action in the presence of water. Usually white in color, these deposits are visible after the water evaporates. Generally, the presence of efflorescence is an indication that there is moisture intrusion in the material and may be a sign of a leak or other potential problem.
The best way to minimize the risk of efflorescence is to use a high-quality concrete sealer. This will reduce the amount of water that can infiltrate and carry soluble salts to the surface. Providing proper drainage and regrading the soil around the area will also minimize moisture migration.
Another preventive measure is to use a class F fly ash or other pozzolan during mixing. This will help to reduce the amount of calcium hydroxide in the concrete, which is responsible for efflorescence. Also, using a steel trowel to achieve a smoother surface will inhibit the movement of water and therefore reduce the chance of efflorescence.
4. Discoloration
Concrete has become a staple in the construction industry due to its durability and versatility. However, concrete isn’t perfect and there are several issues that can affect the appearance of a concrete slab. Some of these issues can be easily fixed, while others may require more time-consuming steps to resolve. Some of the most common issues that commercial concrete contractors encounter are discoloration, scaling, honeycombing, efflorescence, and settlement.
Various factors can cause discoloration in concrete, such as inconsistent mix proportions, water ratios, and poor quality materials. This issue often presents as dark blotches or mottled discoloration on flatwork surfaces or a gross change in color over a large area of a concrete placement.
There are a few different methods to fix discoloration in concrete, but most involve using chemicals. For example, a chemical treatment that uses hydrochloric acid can be used to remove the discoloration from the surface of the concrete. It is important to note that this method can have a negative impact on the durability of concrete, so it should only be used when necessary.
Other chemicals, such as acetic or phosphoric acids, can also be used to reduce discoloration on concrete surfaces. It is important to follow proper safety protocols when using these chemicals, as they can be very hazardous if not handled correctly. Before using any chemical to treat a concrete slab, it is recommended that a small test patch is performed on an inconspicuous area of the concrete to ensure that it won’t have a negative impact on the integrity of the material.
Keeping your concrete looking its best is essential to the overall success of your construction project. By understanding the most common issues that can affect your concrete’s appearance and knowing how to fix them, you can avoid costly mistakes in future projects.
5. Settlement
Concrete is incredibly durable, but it’s not immune to damage. This is especially true of older concrete, where it’s more common for the underlying soil to shift and cause problems. If you’re seeing widespread popouts and spalls on roadways or sidewalks, it may be time to consider replacing the concrete.
This type of damage is more prevalent in transport-related structures, as their failure can lead to inconvenience for motorists and pedestrians. In addition, these issues can also have major health and safety implications.
The underlying soil plays a major role in the stability of concrete slabs. If the soil foundation is not properly compacted, it can shrink or expand with changes in moisture content, causing the concrete to settle and eventually sink. Erosion caused by poor drainage can also remove soil from underneath the foundation, creating voids and leading to sunken concrete.
There are several ways to repair a concrete slab that has settled, and the appropriate method will depend on the severity of the issue. Mudjacking and polyurethane foam injection are quick processes that can be completed in a few hours, while more extensive repairs with helical or concrete piers can take longer.
There are many hazards associated with concrete construction, from falls to chemical burns. But with proper safety protocols in place and a dedication to quality, these risks can be mitigated. As always, if you have any questions or concerns about safety on the job, contact your local team of concrete professionals for expert advice. They can help you avoid the most common construction problems, so that you’re able to create beautiful and long-lasting concrete structures. Emily Folk is a writer with a background in sustainability and green manufacturing. She writes about green living and environmental issues at her blog Conservation Folks.
