AASHTO T 311-20 PDF Download

The AASHTO T 311-20 standard provides a method for determining the grain-size distribution of granular soil materials. The standard specifies the use of a 6.3-mm sieve size for separation, although it allows for the use of alternative sieve sizes if necessary. If an alternative sieve size is used, it should be used consistently throughout the procedure in place of the 6.3 mm size.

The standard outlines the procedure for conducting the grain-size analysis, which involves weighing and sieving the soil sample. The sample is first oven-dried and then sieved through the selected sieve size. The retained material on each sieve is weighed to determine the amount of soil within each size range.

The standard also provides guidance on calculating the grain-size distribution by plotting the results on a semi-logarithmic chart, which allows for the determination of percentages of various particle sizes. Additionally, the standard includes information on reporting the results, including documentation of the sieve sizes used and calculation of cumulative percent passing.