Why do engineers use the California Bearing Ratio in road construction?

Engineers use the California Bearing Ratio (CBR) primarily to assess the strength of subgrade materials. This test indicates how well the soil can support loads imposed by surface traffic, making it an essential factor in the design and construction of roadways. The CBR value helps engineers determine the thickness of the pavement and identify suitable materials for use in construction. A higher CBR value suggests a stronger subgrade, which means less pavement thickness may be required. This correlation allows for effective and economical design of both flexible and rigid pavement structures.

Options that are unrelated, such as determining aesthetic qualities, analyzing environmental impacts, or measuring aggregate colors, do not pertain to the structural integrity and load-bearing capacity of the subgrade materials, which is the primary reason for utilizing the CBR in road construction.