What causes concrete to spall and flake after winter in NB and how can it be repaired?

Concrete spalling and flaking after winter in New Brunswick is primarily caused by freeze-thaw damage from water penetrating the concrete surface, freezing, expanding, and literally breaking off pieces of the surface. This is one of the most common concrete problems in NB due to our punishing Maritime climate with 150+ freeze-thaw cycles annually.

Understanding Spalling in NB's Climate

Spalling occurs when water enters the concrete through tiny pores and cracks, then freezes and expands by 9%. This expansion creates tremendous pressure within the concrete matrix, forcing pieces of the surface to break away. In New Brunswick, this process is accelerated by road salt and de-icing chemicals that lower the freezing point, creating even more freeze-thaw cycles than temperature alone would produce. Salt-laden slush from NB roads splashes onto driveways, walkways, and garage aprons throughout our long winter season, making the problem worse.

The most vulnerable concrete is non-air-entrained concrete — older driveways, sidewalks, and steps poured without proper air entrainment. Air-entrained concrete contains billions of microscopic air bubbles (4-7% air content) that give freezing water room to expand harmlessly. Concrete without these air voids has nowhere for the expanding ice to go except to fracture the surface.

Surface vs. Structural Spalling

Surface spalling affects only the top 1/4 to 1/2 inch of concrete — the surface flakes and scales but the underlying concrete remains sound. This is repairable and primarily cosmetic, though it will worsen each winter if left untreated. Deep spalling extends into the concrete matrix and may expose reinforcement (rebar or wire mesh). Deep spalling indicates more serious concrete deterioration and may require professional assessment, especially on structural elements like foundation walls or load-bearing slabs.

Repair Methods for Surface Spalling

For surface spalling on driveways, patios, and walkways, concrete resurfacer is the most practical repair. Products like Quikrete Concrete Resurfacer or Sakrete Flo-Coat cost $15-$25 per 40-pound bag and cover 40-80 square feet depending on thickness. Clean the spalled area thoroughly with a pressure washer, let it dry completely, then apply the resurfacer with a squeegee or trowel. The new surface bonds chemically to the old concrete and can be textured to match the surrounding area.

For deeper spalling (over 1/2 inch), use a concrete patching compound. Remove all loose material with a hammer and chisel, clean thoroughly, apply a concrete bonding agent, then fill with patching compound. Quikrete Vinyl Concrete Patcher works well for areas up to 2 inches deep and costs $8-$12 per bag.

Prevention is Key

The best spalling repair is prevention. Apply a penetrating concrete sealer every 2-3 years to all exterior concrete in NB. Silane/siloxane sealers ($40-$80 per gallon) penetrate into the concrete and repel water without changing the appearance. This dramatically reduces water penetration and freeze-thaw damage. Never use film-forming sealers (acrylics) on exterior concrete in NB — they can trap moisture and make spalling worse.

Avoid rock salt (sodium chloride) for winter de-icing. Use sand for traction, or if you must use a chemical de-icer, choose calcium magnesium acetate (CMA). Never apply any de-icing chemical to concrete less than one year old.

When to Hire a Professional

Repair surface spalling yourself on non-structural flatwork like patios and sidewalks. Hire a professional for spalling on foundation walls, structural slabs, or when spalling covers more than 25% of the surface area. Extensive spalling may indicate the concrete has reached the end of its service life and needs replacement rather than repair. A professional can assess whether the underlying concrete is sound and recommend the most cost-effective solution.

Need help finding a concrete professional for extensive spalling repair? New Brunswick Concrete can match you with local contractors experienced in NB freeze-thaw damage repair.