12.2 : 耐凍害コンクリート

Concrete is prone to frost damage during freeze-thaw cycles. Air entrainment is one of the strategies employed to enhance frost resistance.

Introducing microscopic air bubbles into the concrete forms small voids that help mitigate the pressure from expanding ice, preventing cracking. The optimal amount of air depends on the concrete's exposure to weather conditions and the aggregate size.

The water cement ratio is another parameter that significantly impacts frost resistance. A lower ratio results in fewer capillaries, reducing the water's ability to freeze and cause damage. This ratio must be carefully managed to maintain the concrete's workability and strength.

Proper curing of concrete is crucial as it promotes complete hydration, increasing the strength and durability of the concrete while minimizing water penetration that could freeze and cause structural damage.

Selecting the right type of aggregate also plays a significant role; high-porosity aggregates can lead to quick water saturation and frost damage, while low-porosity aggregates enhance frost resistance.

Accelerated freeze-thaw tests simulate extreme conditions to rigorously evaluate the resilience and longevity of concrete compared to natural exposure conditions.