What is the required characteristic of concrete used for basement walls exposed to severe weathering?

The requirement for concrete used in basement walls exposed to severe weathering is that it must be air entrained. This characteristic is crucial because air-entrained concrete contains tiny, evenly distributed air bubbles that greatly enhance its durability and resistance to freeze-thaw cycles. In climates where severe weathering occurs, the risk of water penetrating the concrete and then freezing can lead to significant cracking and damage. The air bubbles act as pressure relief zones during freeze-thaw cycles, allowing any trapped water to expand without causing structural harm to the concrete.

While reinforcing concrete is generally a good practice for added tensile strength, it is not specifically required for all basement walls, especially those not exposed to severe conditions. Similarly, coloring the concrete and incorporating recycled materials can be beneficial for aesthetic purposes and sustainability, but these attributes do not directly address the challenges posed by severe weathering. Therefore, air entrainment is the essential characteristic that ensures the concrete can withstand harsh environmental conditions effectively.