What is the difference between air-entrained and non-air-entrained concrete, and which is required for exterior flatwork in NB?

Air-entrained concrete is absolutely mandatory for all exterior flatwork in New Brunswick. Non-air-entrained concrete will fail catastrophically within 3-7 years under NB's punishing freeze-thaw conditions, while air-entrained concrete can last 25-40 years when properly maintained.

Air entrainment creates billions of microscopic air bubbles (4-7% of the concrete's volume) that act as tiny expansion chambers throughout the concrete matrix. When water penetrates the concrete and freezes, it expands by 9% — without these air voids to accommodate the expansion, the freezing water creates internal pressure that fractures the concrete from within. The air bubbles provide relief valves that prevent this destructive internal pressure buildup.

New Brunswick experiences over 150 freeze-thaw cycles annually — among the most severe in Canada. Each cycle forces water into the concrete's pores through capillary action, then freezes and expands, then thaws and contracts. This relentless expansion-contraction cycle is the primary destroyer of concrete in our Maritime climate. Without air entrainment, each freeze-thaw event creates microscopic cracks that grow larger with every subsequent cycle, leading to spalling (surface flaking), scaling (surface peeling), and eventual structural deterioration.

Non-air-entrained concrete is dense and strong in compression, making it suitable for interior applications like basement floors, garage slabs, and interior structural elements where freeze-thaw exposure doesn't occur. However, this density becomes a liability outdoors — water has nowhere to go when it freezes, so the concrete cracks and spalls. You'll see this on older NB driveways, sidewalks, and steps that were poured with standard concrete — the surface looks like it's been attacked with a jackhammer, with chunks flaking off and exposed aggregate showing through.

The cost difference is minimal but the performance difference is dramatic. Air-entrained ready-mix costs only $10-20 more per cubic yard than standard concrete — roughly $50-100 extra for a typical driveway. Compare that to replacing a failed driveway at $4,000-8,000 after just 5-7 years. Air entrainment also improves workability, making the concrete easier to place and finish.

De-icing salt compounds the freeze-thaw problem in NB. Road salt lowers the freezing point of water, creating more freeze-thaw cycles at the concrete surface than ambient temperature alone would produce. Salt-laden slush from NB roads splashes onto driveways and walkways from November through April. Air-entrained concrete combined with a quality penetrating sealer applied every 2-3 years provides the best defense against both freeze-thaw damage and salt attack.

When ordering concrete in NB, always specify: "Air-entrained mix with 4-7% air content for exterior exposure." Any reputable ready-mix supplier knows this is standard for NB exterior work. If a contractor suggests using non-air-entrained concrete for your driveway, patio, or sidewalk to save money, find a different contractor — they're either inexperienced with NB conditions or willing to compromise your project's longevity for short-term savings.

For interior applications like basement floors, garage floors (if heated), and structural elements not exposed to freeze-thaw cycles, non-air-entrained concrete is perfectly appropriate and often preferred for its higher strength and density.

Need help finding a concrete contractor who understands NB's demanding climate conditions? New Brunswick Concrete can match you with local professionals who specify the right materials for Maritime durability.