Concrete driveways are durable, but cracks can develop over time from settling soil, shrinkage during curing, excessive vehicle loads, environmental exposure, and more. Left untreated, these cracks can spread and further deteriorate the driveway. Fortunately, you have several options for repairing concrete cracks, from simple DIY fixes to professional services for major damage. This guide will explore the causes of concrete driveway cracks, how to evaluate the damage, and various repair methods, with a focus on using QUIKRETE sealers for DIY repairs.
Why Do Concrete Driveways Develop Cracks?
Understanding the reasons behind concrete cracking can help you with concrete installation and maintenance. Several factors contribute to the formation of cracks in concrete driveways.
Natural Shrinkage During Curing
Concrete is mixed with excess water to facilitate the placement and consolidation of the slab or form. As concrete cures, it naturally shrinks, creating internal tension. When this tension exceeds the concrete’s strength, cracks can form. This is commonly referred to as drying shrinkage.
Soil Settlement and Movement
Installing concrete means disturbing the soil beneath the driveway, leading to settling or shifting. This can cause stress on the concrete, resulting in cracks. Even in undisturbed soil, the additional weight of the concrete can cause the soil to compact and settle, weakening support for the slab and causing stress-induced cracking.
Poor Joint Control Spacing
Control joints are the cuts that we commonly see in concrete slabs. They reduce thermal stresses in the concrete. Inadequate spacing between control joints can result in uneven stress distribution, increasing the likelihood of cracking.
Excessive Vehicle Loads
Concrete is strong, but it has its limits. Unreinforced concrete, such as a driveway, can crack under sufficient load. Heavy equipment and vehicles with weight beyond the design limit of the driveway will cause cracks to develop over time.
Freeze-Thaw Cycles
In colder climates, repeated freezing and thawing of water within the concrete can cause expansion and contraction, leading to cracks. Because water expands when it freezes, the frozen ground heaves upward, creating additional stress on the slab.
Subgrade Preparation Issues
Good concrete work includes proper preparation of the soil beneath the concrete. Poorly prepared subgrade or inadequate compaction can result in uneven support for the concrete, leading to crack formation.
Exposure to Chemicals
Despite being hard, concrete is porous, which means it will absorb liquids. Concrete driveways regularly exposed to chemicals, such as de-icing salts or oil spills, can weaken over time. These substances penetrate the surface, reacting with the concrete to exacerbate cracking.
Evaluating Concrete Crack Damage
Not all driveway cracks require immediate repair. Assess the severity of the damage to determine the appropriate course of action. Below are key factors to consider when evaluating concrete cracks.
Crack Width
Very fine hairline cracks under ⅛ inch wide may not need repair. Monitor medium cracks between ⅛ and ½ inch wide closely. Major cracks wider than ½ inch likely require professional attention.
Growth Over Time
Periodically measure identified cracks and mark their ends with a grease pencil. Growth indicates ongoing movement and may require more urgent repair. If a crack is going to grow, you can expect it to happen during season changes when the weather goes from hot to cold or vice versa. Winter especially draws out cracks because the ground freezes and expands.
Horizontal Movement
Use a rigid straightedge to check for separation between the two sides of the crack. Parallel movement can signify uneven settling or shifting of slab segments.
Crack Location
Cracks along control joints and edges are generally less concerning than random cracks through the middle of slab segments. Concrete is naturally weaker along joints and edges, so cracking in those areas isn’t unexpected. Cracks through the middle of the slab indicate movement in the subgrade or weakness in the concrete, making them a more serious problem.
Vertical Displacement
Check for misalignment of crack edges, which indicate shearing stress. Significant vertical displacement over ¼ inch often suggests substantial soil movement or freeze-thaw damage. It can also indicate poorly prepared subgrade.
Frequency of New Cracks
The frequent appearance of new cracks in the same area might hint at a deeper, unresolved problem requiring further investigation or professional assessment. The concrete may be brittle from chemical absorption or improper mixing, or there may be a persistent problem in the subgrade.
We suggest inspecting your driveway surface for other signs of deterioration like pitting, crumbling edges, sinking, or prominent joints that cause trip hazards. These issues may need extensive repairs beyond basic crack filling.
DIY Concrete Crack Repair Options
You can attempt temporary repairs using readily available products for minor surface cracks up to ¼ inch wide. These solutions provide quick fixes, but you may need to reapply them after one or two years.
Silicone and Acrylic Latex Caulk
Latex caulk works well for narrow cracks but lacks durability for wider repairs or moving cracks. It’s used when cracks are cosmetic and caused by minor issues like drying shrinkage. Latex caulk is simple to apply and available at most big box and local hardware stores.
Hydraulic Cement
Premixed cement-based products that harden when exposed to moisture are suitable for stationary hairline cracks. These tend to blend better with the texture of the existing concrete as opposed to other crack fillers like silicone. Because they’re essentially thinned concrete and thus naturally weak, following the instructions carefully is important to prevent the repair from crumbling or cracking.
Vinyl Concrete Patchers
Acrylic-based compounds with thicker viscosity fill wider cracks up to ¼ inch but may not provide long-term strength. Use these after addressing the underlying issue that caused the cracking so the crack stabilizes and doesn’t continue shifting or widening.
Epoxy Crack Fillers
The most durable DIY option, epoxy fillers work well for cracks up to ¼ inch wide in relatively stable locations. Epoxy is fairly similar to vinyl for crack filling, so either option works well.
Ready-Mix Concretes
These are convenient choices for filling and repairing slightly larger cracks, particularly those with a depth extending into the concrete slab. By conforming to the crack shape and hardening quickly, they seal effectively and create a seamless finish that matches closely with the existing concrete.
QUIKRETE Concrete Crack Sealers: A Reliable Solution
QUIKRETE offers a range of waterproofing sealers designed to protect and enhance concrete, brick, masonry, pavers, stone, and stucco surfaces.
Concrete & Masonry Waterproofing Sealer
QUIKRETE Concrete & Masonry Waterproofing Sealer’s water-based silicone formulation provides excellent water resistance without altering the surface appearance. It’s ideal for concrete, pavers, and stucco, leaving a natural-looking finish.
Concrete & Masonry High Gloss Sealer
A water-based, high-gloss acrylic sealer that waterproofs, seals, and enhances surface color, QUIKRETE Concrete & Masonry High Gloss Sealer is suitable for concrete, pavers, masonry, brick, and natural stone, providing a beautiful wet-look finish.
Benefits of Using QUIKRETE Sealers
The application of QUIKRETE sealers extends beyond superficial aesthetics. These sealers offer resilience against harsh weather, protect against moisture penetration, and discourage damage from freeze-thaw cycles, ensuring long-term driveway protection.
How to Apply QUIKRETE Sealers
Proper application of QUIKRETE sealers is essential for effective concrete protection:
- Let the concrete cure for at least 30 days before applying sealer to newly poured surfaces.
- Clean the surface thoroughly, removing all stains and flaking material.
- Verify surface porosity by placing water drops on the concrete. If the water absorbs, the surface is ready for sealer application.
- Apply the sealer using a roller, water sprayer, or brush. Both waterproofing and high-gloss sealers are ready to use.
- If needed, apply a second coat 10 to 15 minutes after the first coat while it’s still wet.
- Allow adequate drying time, typically 24 to 48 hours, before allowing any foot or vehicle traffic. This gives the sealant time to fully penetrate and harden.
The video below provides an example of applying a QUIKRETE sealer.
Professional Repair for Severe Concrete Damage
In cases of extensive cracking, spalling, sinking, or widespread spider cracking, professional intervention may be necessary. Consider professional repair services for:
- Trip hazards from slab sections lifting more than an inch above adjacent sections
- Cracks wider than one inch, indicating significant soil movement
- Sunken areas over two inches deep where mudjacking isn’t practical
- Deep, full-depth cracks and damage at slab edges
Professional concrete section replacement typically costs $6–$14 per square foot, according to Angi. The process involves cutting out and repouring the flawed section. The repair is usually quick, but the new concrete will require a few weeks to fully cure.
Address the underlying cause of the damage before pouring new concrete to prevent rapid crack recurrence. This may involve soil compaction or stabilization beneath the concrete.
New Technologies in Concrete Repair
Innovative approaches and materials in concrete repair have improved the resilience and life expectancy of driveways:
- Fiber Reinforced Concrete: This technique integrates fibers into the concrete mix to enhance tensile strength and reduce cracking potential.
- Polyurethane Injections: An advanced method to lift and stabilize sunken slabs efficiently without extensive excavation.
- Sealant Enhancers: Additives in sealants now offer improved durability and bonding to concrete surfaces, extending the protective life of sealers.
Preventing Future Concrete Cracks
While some minor shrinkage cracks are inevitable in concrete slabs, several measures can help minimize cracking. Prepare the subgrade well and stabilize the foundation to reduce soil movement. Use proper concrete mix design and the appropriate concrete thickness for the intended load. When pouring the slab, keep correct control joint spacing.
Regular maintenance and prompt repair of minor issues can also prevent small cracks from developing into major problems. Periodic inspections and modern preventative sealers can effectively extend the lifespan of the concrete surface.
