Understanding Concrete's Frost Resistance: A Tale of Temperature and Air

The Belt and Road strategy has boosted infrastructure in the Qinghai-Tibet Plateau's permafrost region. This means concrete there needs to be stronger and better at withstanding freezing temperatures. Researchers tested how concrete cured at different temperatures handles freezing and thawing cycles. They found that as the curing temperature drops, the concrete gets weaker. For example, concrete cured at standard temperatures for 28 days was as strong as concrete cured at 5°C for 56 days or at -3°C for 84 days. The more air bubbles in the concrete, the weaker it gets.At 0. 08% air content, the concrete was the weakest. The more freeze-thaw cycles concrete goes through, the more its tiny pores change, making it less durable. Concrete cured at lower temperatures was worse at resisting freezing and thawing compared to standard curing. Interestingly, there's an optimal air content, around 3. 6%, where concrete is best at handling freezing temperatures. Too little or too much air makes the concrete weaker. This study also created a model to predict how concrete behaves when cured at lower temperatures.