• AASHTO SOIL CLASSIFICATION (by AASHTO) AASHTO = American Association of state Highway and Transport Officials Situation 2 Classification of Highway Subgrade Materials % FINER SOIL B SIEVE General classification Granular materials (35 or less of total sample passing No. 200) SOIL A SOIL C 10 83 100 90 A-1 A-2 Procedure: 76 Group classification A-1-a A-I-b A-3 A-2-4 A-2-5 A-2-6 A-2-7 40 48 92 O Group Classification • with required test data in minol, proceed from left to right, inchart. The correct group will be found by process of elimination. The first group from the left consistent with the test dlatta is the conect classficaton. 200 20 86 34 Sieve analysis (percentage passing) No. 10 No. 40 LL 20 70 37 50 man 30 max. 15 max. 50 max 25 max. 51 min. 10 max PI 5 32 18 35 max 35 max. No. 200 Characteristics of fraction 35 max. 35 mas. Using AASHTO method: 1. Determine the group symbol and index for soil A. 2. Determine the group symbol and index for soil B. 3. Determine the group symbol and index for soil C. passing No. 40 Liquid limit Plasticity index Usual types of significant 40 max 41 min. 40 max. 41 min. 6 max. Stone fragments gravel, and sand Il min. Siky or clayey gravel and sand Il min. NP 10 max. 10 max. O Group Index Fine constituent materials sand General subgrade rating GI=(Fco-35)(00OBLL) +a01(Fa00-15)(PI-10) • if the equation has a negatve value, GI ISO. • the group index number calculated from the equatton Is rounded off to the nearest whole number (note: round off) • the group index number for soil groups, namely: (A-1-a, A-s-b, A-3, A-2-4, A-2-5) is O. • when calaulating the GI for sols that belong to groups A2-6 ard A-2-7, use portial GI(for PI): GI= 0.01(Faco-15XPI-10) Excellent to good Silt-clay materials (more than 35 of total sample passing No. 200) General classification A-7 A-7-5 A-7-6 Group classification A-4 A-5 A-6 Sieve analysis (percentage passing) No. 10 No. 40 No. 200 Characteristies of fraction passing No. 40 Liquid limit Plasticity indes Usual types of significant constituent materials General subgrade rating 36 min. 36 min. 36 min. 36 min. 40 max. 10 max 41 min 10 max 40 max Il min. Clayey soils 41 min. Il min. . Silty soils Fair to poor