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Material Properties. Material Types Unbound (soil) Natural (i.e., subgrade) Select (i.e., subbase, base) Asphalt concrete Portland cement concrete Stabilized.

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Presentation on theme: "Material Properties. Material Types Unbound (soil) Natural (i.e., subgrade) Select (i.e., subbase, base) Asphalt concrete Portland cement concrete Stabilized."— Presentation transcript:

1 Material Properties

2 Material Types Unbound (soil) Natural (i.e., subgrade) Select (i.e., subbase, base) Asphalt concrete Portland cement concrete Stabilized materials Cement stabilized Bituminous stabilized Bedrock Recycled

3 Material Properties Needed for Design Pavement response model material inputs Modulus (stiffness) Poisson’s ratio Materials-related pavement distress criteria Permanent deformation resistance Fatigue resistance Strength Other materials properties Density Permeability Thermal expansion coefficient

4 Material Models (Yoder and Witczak, 1974)

5 Material Models Linear elasticity Asphalt Stabilized layers Unbound layers Linear viscoelasticity Asphalt Nonlinear (all materials, to some extent) Nonlinear elasticity Plasticity Nonlinear viscoelasticity Viscoplasticity

6 Soil Classification Systems

7  T he separation of soil into classes or groups each having similar characteristics and potentially similar behaviour  Few simple (routine) tests are used to classify soils.  Gradation  Atterberg Limits

8 Soil Classification Systems MIT AASHTO USCS FAA

9 MIT Classification MaterialSize (mm) Boulder> 60 Gravel Fine2 – 6 Medium6 – 20 Coarse20 – 60 Sand Fine0.06 – 0.2 Medium0.2 – 0.6 Coarse0.6 – 2 Silt Fine0.002 – 0.006 Medium0.006 – 0.02 Coarse0.02 – 0.06 Clay< 0.002

10 AASHTO Classification AASHTO: American Association of State Highways and Transportation Officials Used mainly for subgrade rating for highway purposes. Requires:  Gradation  LL  PI

11 AASHTO Classification (Granular Materials)

12 AASHTO Classification (Fine Materials)

13 AASHTO Classification (Coduto, 1999)

14 Group Index (GI) GI is used to classify the fine grained soils within one group and for judging their suitability as subgrade materials. GI = 0.2 a + 0.005 a.c + 0.01 b.d  (0 to 20) a = %P#200 – 35  (0 to 40) b = %P#200 – 15  (0 to 40) c = LL – 40  (0 to 20) d = LL – 10  (0 to 20) GI to the nearest whole number (integer) High GI  low quality material EX: A-7-6(5), A-7-6(18)

15 USCS Classification USCS: United Soil Classification System Used mainly for geotechnical purposes Requires:  Gradation  LL  PI

16 USCS Classification SoilSymbolPropertySymbol GravelGWell GradedW SandSPoor GradedP ClayCHigh LL (High Plasticity)H SiltMLow LL (Low Plasticity)L PeatPtClayC Organic soilOsiltM EX: SC  Clayey Sand EX: Dual Symbol: SP-SM GW  Well Graded Gravel poorly graded sand CL  Clay with low plasticity with silt

17 Computing CU and CC Coefficient of Uniformity Coefficient of Curvature High Values Indicate Well- Graded Soil Values Between 1-3 Indicate Well-Graded Soil

18 A-Line Chart Separates Clays and Silts ML & OL OH & MH

19 USCS Classification

20 USCS Classification (Coarse-Grained) Coarse- Grained Soils 50% or less pass #200 % P #4 < 50% (Gravel) Less than 5% Fines Cu>4, Cc = (1-3)GW Not satisfying GWGP More than 12% Fines Below A-LineGM PI>7& Above A- Line GC % P #4 > 50% (Sand) Less than 5% Fines Cu>6, Cc = (1-3)SW Not satisfying GWSP More than 12% Fines Below A-LineSM PI>7& Above A- Line SC

21 USCS Classification (Fine-Grained) Fine- Grained Soils More than 50% pass #200 LL<50% ML CL OL LL>50% MH CH OH Highly Organic SoilsPt OH & MH ML & OL

22 USCS Dual Symbols For the following conditions a dual symbol should be used: a) Coarse grained soils with % fines between 5% and 12% The first symbol is indicative of the gradation (W or P), the second symbol is indicative of the fines. EX: SP-SM poorly graded sand with silt b) Fine grained soils within the shaded zone in the A-line chart (PI between 4 and 7, LL between 12 and 25). EX: CL-CM, Silty clay with Low LL

23 Comparison between the AASHTO and Unified Systems Both systems are based on the texture and plasticity of the soil. Both systems divide the soils into two major categories: Coarse grained and Fine grained based on %P#200 SI sieve. AASHTO: %P#200 < 35%  Coarse grained %P#200 > 35%  Fine grained Unified: %P#200 < 50%  Coarse grained %P#200 > 50%  Fine grained

24 Comparison between the AASHTO and Unified Systems (Cont’d) AASHTO: #10 sieve separates gravels and sand Unified: #4 sieve separates gravels and sand AASHTO : There is no organic soil Unified : There is organic soil AASHTO: gravely and sandy soils are not clearly separated Unified: gravely and sandy soils are clearly separated

25 (NCHRP 1-37A. 1999)

26 (Das, 1990)

27 FAA Classification FAA: Federal Aviation Administration Used mainly for soil classification for airport construction. Requires :  Gradation  LL  PI

28 FAA Classification (Yoder & Witczak 1975) Soil Group % R#10%P#10, R#60 %P#60, R#270 %P#270LLPI E-10-4540+60-15-25-6- E-20-4515+85-25- 6- E-30-45--25- 6- E-40-45--35- 10- E-50-55--45-40-15- E-60-55--45+40-10- E-70-55--45+50-10-30 E-80-55--45+60-15-40 E-90-55--45+40+30- E-100-55--45+70-20-50 E-110-55--45+80-30+ E-120-55--45+80+- E-13Muck and Peat – Field Examination

29 FAA Classification Chart for Fine-Grained Soils (Yoder & Witczak 1975)

30 It is Hard to be an engineer!


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