For how many days should a CBR sample be soaked before testing?

Soaking a California Bearing Ratio (CBR) sample is a critical step in the testing procedure because it significantly influences the soil's moisture content and its ability to simulate field conditions. The correct soaking period, which is generally accepted in standards for CBR testing, is typically 4 days. This duration allows the soil sample to adequately absorb water and reach saturation, ensuring that the results of the test will reflect the material's performance under similar conditions in actual field scenarios.

Soaking the sample for 4 days helps to achieve uniform moisture distribution throughout the sample, enabling a more accurate assessment of the soil's strength and bearing capacity. It reflects the conditions that the materials would experience in real-world applications, particularly in subgrade evaluations for pavement design and other infrastructure projects.