Unbound aggregate base and subbase layers distribute wheel load induced stresses to
protect subgrade. Standards such as AASHTO and individual states specifications have set
several quality control limits for a variety of properties of aggregates used in the pavement
base and subbase courses. Most standards and DOT specifications suggest that the ratio of
percent passing No. 200 sieve to percent passing No. 40 sieve should not be greater than
two thirds, and plasticity index of the material passing No. 40 sieve should be less than 6 …