The Ultimate Guide to Fixing Cracks in Concrete Sidewalks

What are Concrete Sidewalks?

Concrete sidewalks are a common surface for walkways because concrete is a durable material when properly installed and maintained. A standard residential sidewalk is usually four to six inches thick and constructed of a mixture of cement, sand, and gravel or crushed stone called aggregate. This mix forms a hardened surface that can support weight while being weather resistant.

Why Cracks Form in Concrete Sidewalks

There are a few key reasons why cracks may develop in concrete walkways, even when installed properly:

• Movement and vibrations: Like foundations of buildings, concrete sidewalks are subject to the settling and minor shifting of soils over many years. This can generate cracks, especially if there is an underlying unstable base.
• Temperature changes: As concrete heats up and cools down from daily temperature fluctuations, it expands and contracts slightly. Over many cycles this repetitive stress can lead to cracking.
• Moisture intrusion: When water gets absorbed into concrete, it causes the material to expand. If water then evaporates from the surface but is still trapped deeper inside, it will try to contract more than the outer layers—causing stresses.
• Late-season freezing temperatures: If concrete is poured late in the year when cold weather is approaching, it may not have time to fully cure before the first freezes arrive. Ice expansion during freezing cycles can then crack uncured concrete.
• Material weaknesses: Issues like low cement content, too much water in the mix, or flaws in the aggregate can produce weaker areas susceptible to cracking even under minimal stresses.

Identification of Concrete Cracks

Properly identifying the specific crack is important for determining the best repair approach. Here are some common crack types to watch for in concrete sidewalks:

• Thin, hairline cracks: These very narrow cracks often indicate minor drying shrinkage or minor settling/movement.
• Medium cracks: Wider cracks up to 1/4 inch can signal more substantial movement, freezing, or material weaknesses at certain points.
• Large or wide cracks: Gaps over 1/4 inch usually mean serious issues like structural failure of all or part of the sidewalk. Replacement may be necessary.
• Mesh or networked cracks: A complex interconnected web of cracks points to significant foundation settling or other foundation problems beneath the sidewalk.
• Spalling or crumbling edges: Areas where the concrete edge crumbles indicate internal deterioration, usually from freeze/thaw or moisture damage.

Types of Cracks That Can Occur in Concrete

There are a few main types of cracks to be aware of:

• Control cracks: Intentional cracks spaced periodically to control where random cracks may form due to stresses.
• Shrinkage cracks: Develop as concrete cures due to drying and chemical shrinkage of the cement binder. Often narrow.
• Thermal cracks: Result from thermal expansion/contraction cycles as concrete heats up and cools down. May form parallel to edges.
• Reflective cracks: Mirror cracks appearing in new concrete above existing cracks in underlying surfaces like asphalt or concrete.
• Structural cracks: Indicate a serious issue caused by settlement, foundation movement or other displacement of the slab. May need partial or full replacement.

Assess the Severity

Once you have identified all cracks present, the next important step is to gauge the severity of each one to determine an appropriate repair approach. Here are some factors to consider when evaluating crack severity:

• Crack width: Narrow cracks under 1/8 inch are minor, 1/4 inch or wider indicates a significant problem.
• Crack pattern and location: Are cracks isolated or networked? Near or crossing a joint or edge? This shows why it cracked.
• Concrete spalling or crumbling: Severe moisture/freeze damage near a crack makes repair alone ineffective.
• Crack depth: Use a flathead screwdriver to test depth. Shallow is better than cracks extending through half the slab depth.
• Concrete lifting or shifting: Major movement means part or all needs replacing, not just surface crack repairs.
• Age of concrete: Older sidewalks show cumulative damage and may be distorted due to repeated settlement.

When to Fix Cracks vs When to Replace the Entire Sidewalk?

The severity of the cracks will determine whether repair or replacement of the sidewalk is necessary. Hairline cracks less than 1/8 inch deep can usually be cleaned and filled with concrete crack filler. Small shallow cracks between 1/8 to 1/4 inch may only require repair of isolated issues, while multiple or intersecting cracks in this range could mean replacement is better. Cracks wider than 1/4 inch will likely require replacing the entire section since repairs won’t be very durable. Sections with significant deterioration, crumbling, or structural issues also need replacement as do areas with extensive networked cracking patterns or major lifting and shifting of the surface.

When to Seek Professional Concrete Sidewalk Repairs?

For larger or complex sidewalk crack repairs, it’s often best to hire a professional contractor. Specialized tools and equipment or situations that require adherence to building codes justify bringing in experts. Professionals are needed if there are extensive cracks over large areas like more than 3-4 feet. Structural cracks pointing to foundation issues or cracks wider than 1/4 inch also warrant professional assistance. Heaved, settled or severely deteriorated sections along with repairs using specialized demolition or tooling should also be handled by contractors. Tight timelines or lack of one’s own resources and abilities also indicate the job is best left to experienced concrete pros.

How Professionals Fix the Sidewalk Cracks

Once a contractor has thoroughly assessed your sidewalk, they will employ standardized techniques to effectively repair cracks. Here are the typical steps:

Preparation

The contractor will first clean out the crack using dustless concrete saws or crack chasers to create a clean, keyed edge for materials to bond to. They may also use diamond-tipped blades or grinding wheels to widen and square off any irregular cracks.

Nearby dirt, debris and loose concrete will be removed using hammer and chisel or pneumatic tools. Edges around the repair zone are then sharp-cut using an angle grinder to avoid feathered edges that won’t hold new materials.

Techniques for Applying Repair Material

Common concrete crack fillers and repair compounds are utilized for various repair scenarios:

• Epoxy injections for sealing cracks and bonding new concrete patches. Injected under pressure to displace moisture.
• Liquid urethane and polymer crack repair fillers are troweled or squeegeed into cracks to seal and strengthen them.
• Concrete patching compounds are used for larger cavity repairs. Premixed and poured or hand-tamped into sawcut edges.
• Mortar or rapid-setting concrete may be hand-troweled or sprayed into sizable voids needing structural integrity.

Spreading and Smoothing Repair Compounds

After materials are applied, the contractor levels and smooths the surface using a margin trowel or wooden float. They ensure full bonding contact between new and existing concrete without any air pockets.

Drying and Curing Process

The final stage is allowing curing time for materials to fully harden. Contractors may lightly mist cured concrete sealers or cover patches with a wet blanket for a day or more to retain moisture vital for strength development.

Maintenance Tips to Prevent Further Damage

Proper maintenance after initial repairs will help slow concrete deterioration in the future. Here are some tips for ongoing sidewalk care.

• Examine for tripping or lifting hazards twice annually
• Inspect for cracking after seasonal temperature changes
• Jet wash concrete to remove deicing salts in winter/spring
• Re-seal cracks every 3-5 years using suitable sealant
• Fill settlement cracks promptly before moisture penetrates

Avoid:

• Prolonged puddles that promote moisture intrusion
• Excess soil or mulch piled against sidewalk edges
• Vegetation growing directly on concrete surfaces
• Heavy vehicles driving or parking on sidewalk areas
• Deicing chemical overuse or lack of proper wash away
• Rapid changes in irrigation patterns near sidewalks

Professional Concrete and Masonry in Fredericton

For over 15 years, Atlantic Brick and Stone has been providing top-quality concrete and masonry repair services throughout Fredericton, New Brunswick. As a full-service masonry contractor, we are capable of all types of projects from new commercial and residential construction through to repair work. Our experienced team can assess any sidewalk crack or damage issues and provide expert recommendations on the best repair or replacement solutions.

We at Atlantic Brick and Stone take pride in our reliable craftsmanship. All of our concrete repair work comes with a multi-year warranty to ensure customer satisfaction. Whether you need a simple crack fixed, sections replaced, or a completely new sidewalk installation, we can efficiently handle the job. We also offer masonry services such as stone veneer, brick patio and fireplace installations. Contact us for a free estimate on any concrete or masonry needs. Customers praise our professionalism, quality work, and standing behind our work with strong warranties.