Clay Mineralogy

1
Clay Mineralogy

• Rule .1941 (a3)

2
Rationale of Rule

• Clay mineralogy affects
• The degree to which some soils swell when wetted
• Thereby affecting the number of pores
• Thereby affecting sewage movement through soil
• Therefore
• Clay mineralogy affect loading rate

3
Types of clay

• 11 Clays (such as kaolinite)
• Do not expand on wetting
• 21 Clays, including mixed mineralogy clays (e.g.
  mix of kaolinite and montmorillonite)
• Shrink and swell when dried and wetted

4
Determination of clay minerals (in clay-sized
fraction)

• Based on Soil Taxonomy, Appendix 1
• Field evaluation is done first!
• Laboratory determination MAY be substituted
• Moist consistence AND
• Wet consistence

5
Field Evaluation

• Is done first!
• Moist consistence AND
• Wet consistence

6
Laboratory Determination

• MAY BE used
• ASTM D-4318, Procedures A and B
• Liquid limit
• Plastic limit
• Plasticity index

7
Clay mineralogy classification

• Slightly expansive clay mineralogy
• Expansive mineralogy

8
Slightly Expansive Clay Mineralogy

• Moist Consistence
• Very friable,
• Friable, or
• Firm
• AND
• Wet Consistence
• Slightly sticky to sticky, and
• Nonplastic to plastic
• 11 clay mineral predominated
• Soil is SUITABLE for clay mineralogy

9
Expansive Clay Mineralogy

• Moist Consistence
• Very firm, or
• Extremely firm
• OR
• Wet Consistence
• Very sticky, or
• Very plastic
• 21 clay minerals predominated
• Soil is UNSUITABLE for clay mineralogy

10
Examples

• Bt horizon is
• Friable
• Moderately sticky
• Moderately plastic
• SUITABLE

11
Examples

• Bt horizon is
• Friable
• Moderately sticky
• Moderately plastic
• SUITABLE

12
Examples

• Bt horizon is
• Firm
• Slightly sticky
• Slightly plastic
• SUITABLE

13
Examples

• Bt horizon is
• Very firm
• Very sticky
• Very plastic
• UNSUITABLE

14
Examples

• Bt horizon is
• Very firm
• Very sticky
• Very plastic
• UNSUITABLE

15
Examples

• Bt horizon is
• Very firm
• Moderately sticky
• Moderately plastic
• UNSUITABLE

16
Examples

• Bt horizon is
• Firm
• Very sticky
• Moderately plastic
• UNSUITABLE

17
Examples

• Bt horizon is
• Firm
• Moderately sticky
• Very plastic
• UNSUITABLE

18
What about other adjustments to LTAR?

• No guidance given in rules
• Option given in next few slides

19
Possible LTAR Adjustments
20
Possible LTAR Adjustments
21
Possible LTAR Adjustments
22
Possible LTAR Adjustments
23
Note
24
Estimating Clay Mineralogy from Consistence and
Color
25
ASTM D-4318, Procedures A and B

• If
• Liquid limit gt 50 and
• Plasticity limit gt 30
• The soil shall be considered to have
• EXPANSIVE MINERALOGY

26
Examples

• Bt horizon is
• Friable
• Moderately sticky
• Moderately plastic
• SUITABLE
• Would you run a laboratory test?
• NO

27
Examples

• Bt horizon is
• Firm
• Slightly sticky
• Slightly plastic
• SUITABLE
• Would you run a laboratory test?
• NO

28
Examples

• Bt horizon is
• Very firm
• Very sticky
• Very plastic
• UNSUITABLE
• Would you run a laboratory test?
• MAYBE

29
Examples

• Bt horizon is
• Firm
• Very sticky
• Moderately plastic
• UNSUITABLE
• Would you run a laboratory test?
• YES

30
Example

• Liquid limit 58
• Plastic limit 32
• UNSUITABLE

31
Example

• Liquid limit 45
• Plastic limit 25
• SUITABLE

32
Example

• Liquid limit 58
• Plastic limit 25
• SUITABLE

33
Example

• Liquid limit 45
• Plastic limit 32
• SUITABLE

34
Other Options?

• .1948d
• Ksat
• Apparent CEC
• X-ray diffraction
• COLE

35
Summary

• Field test is done first
• Only if field test indicates unsuitable then
• Laboratory test may be run
• ASTM currently in rules
• Others may be used