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AASHTO SOIL CLASSIFICATION SYSTEM <br />AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATION OFFICIALS <br />Classification of Soils and Soil -Aggregate Mixtures <br />Granular Materials <br />Silt -Clay Materials <br />General Classification <br />(35% or less passing No. 200 sieve) <br />(More than 35% passing No. 200 sieve) <br />A-1 <br />A-2 <br />A-7 <br />Group Classification <br />A-7-5 <br />A-1-a <br />A-1-b <br />A-3 <br />A-2-4 <br />A-2-5 <br />A-2-6 <br />A-2-7 <br />A-4 <br />A-5 <br />A-6 <br />A-7-6 <br />Sieve Analysis, Percent passing: <br />No. 10(2.00 mm)............................. <br />50 max. <br />.... <br />.... <br />.... <br />.... <br />.... <br />.... <br />.... <br />.... <br />.... <br />.... <br />No. 40 (0.425 mm) ............................ <br />30 max. <br />50 max. <br />51 min. <br />.... <br />.... <br />.... <br />.... <br />.... <br />.... <br />.... <br />.... <br />No. 200 (0.075 mm) ............................ <br />15 max. <br />25 max. <br />10 max. <br />35 max. <br />35 max. <br />35 max. <br />35 max. <br />36 min. <br />36 min. <br />36 min. <br />36 min. <br />Characteristics of Fraction Passing No. 40 (0.425 mm) <br />Liquid limit ................................... <br />.... <br />.... <br />40 max. <br />41 min. <br />40 max. <br />41 min. <br />40 max. <br />41 min. <br />40 max. <br />41 min. <br />Plasticity index ............................... <br />6 max. <br />N.P. <br />10 max. <br />10 max. <br />11 min. <br />11 min. <br />10 max. <br />10 max. <br />11 min. <br />11 min. <br />Usual Types of Significant Constituent Materials <br />Stone Fragments, <br />Fine <br />Silty or Clayey Gravel and Sand <br />Silty Soils <br />Clayey Soils <br />Gravel and Sand <br />Sand <br />General Ratings as Subgrade .................... <br />Excellent to Good <br />Fair to Poor <br />The placing of A-3 before A-2 is necessary in the "left to right elimination process" and does not indicate superiority of A-3 over A-2. <br />Plasticity index of A-7-5 subgroup is equal to or less than LL minus 30. Plasticity index of A-7-6 subgroup is greater than LL minus 30. <br />Group A-8 soils are organic clays or peat with organic content >5%. <br />PLASTICITY INDEX (PI) <br />10 20 30 40 50 60 70 <br />90 <br />80 <br />70 <br />E 60 <br />J <br />SF 50 <br />J <br />40 <br />30 <br />20 <br />10 <br />Liquid Limit and Plasticity Index Ranges for the <br />A-4, A-5, A-6 and A-7 Subgroups <br />Definitions of Gravel, Sand and Silt -Clay <br />The terms "gravel", "coarse sand", "fine sand" and "silt -clay", as <br />determinable from the minimum test data required in this <br />classification arrangement and as used in subsequent word <br />descriptions are defined as follows: <br />GRAVEL - Material passing sieve with 3-in. square openings and retained on <br />the No. 10 sieve. <br />COARSE SAND - Material passing the No. 10 sieve and retained on the No. <br />40 sieve. <br />FINE SAND - Material passing the No. 40 sieve and retained on the No. 200 <br />sieve. <br />COMBINED SILT AND CLAY - Material passing the No. 200 sieve <br />BOULDERS (retained on 3-in. sieve) should be excluded from the portion of <br />the sample to which the classificaiton is applied, but the percentage of such <br />material, if any, in the sample should be recorded. <br />The term "silty" is applied to fine material having plasticity index of 10 or less <br />and the term "clayey" is applied to fine material having plasticity index of 11 or <br />greater. <br />/ <br />/ <br />A�GSo4p <br />/ <br />/ <br />/ <br />/// <br />/ <br />6 <br />A-5 <br />/ <br />o <br />A-7 <br />A-4-A-6-r <br />0- <br />GROUP INDEX CHART <br />Group Index (GI) = (F-35) L0.2+0.005 (LL-40) ] + 0.01 (F-15) <br />(PI-10) where F = % Passing No. 200 sieve, LL = Liquid <br />Limit, and PI = Plasticity Index. <br />When working with A-2-6 and A-2-7 subgroups <br />the Partial Group Index (PGI) is determined from the <br />PI only. <br />40 When the combined Partial Group Indices are <br />negative, the Group Index should be reported as zero. <br />>� 30 <br />o <br />Z <br />�K� ^� <br />Qs <br />20 <br />op ^cP 6J�0 <br />10 <br />-10 <br />xam I Then: <br />82 % Passing No. 200 sieve PGI = 8.9 for LL <br />LL = 38 PGI = 7.4 for PI <br />PI=21 0I=16 <br />z <br />z <br />Cr <br />a <br />z <br />w <br />L <br />LL <br />w <br />Q. <br />01CLS022 (07/11) <br />AMERICAN ENGINEERING TESTING, INC. <br />130 <br />