Basement concrete walls require a minimum rest at 30 days of:

The correct choice highlights that basement concrete walls are typically required to achieve a minimum compressive strength of 3000 psi after a curing period of 30 days to ensure structural integrity and durability.

In construction, the specified compressive strength of concrete is crucial for different structural applications. For reinforced concrete walls, especially in basements where water resistance and structural support are necessary, a strength of 3000 psi is recognized as the minimum standard. This strength ensures that the concrete can withstand the pressures exerted by soil, water, and additional loads.

Concrete typically gains its strength over time as it cures; therefore, a 30-day rest period allows the concrete to approximately reach this minimum compressive strength. While options with higher psi values, such as 4000 psi, might be suitable for certain applications requiring more robustness, the construction code allows 3000 psi as the baseline for common basement wall requirements.

The lower options, like 2000 psi or 1000 psi, are insufficient for structural integrity in this context, particularly concerning the conditions that basement walls are subjected to, which include potential moisture exposure and earth pressure. Thus, they do not meet the safety and performance standards necessary for such structures.