05 - soil stabilization

8/3/2019 05 - Soil Stabilization

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Soil Stabilization


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Soil Stabilizers Quicklime: CaO

Lime Kiln Dust: CaO Hydrated Lime: Ca(OH)2

Cement: CaO, SiO2, Al2O3 Cement Kiln Dust: CaO, SiO2, Al2O3

Class C Fly Ash: CaO, SiO2, Al2O3 Class F Fly Ash: SiO2, Al2O3

Source: PCA R&D Serial No. 2435


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Lime Stabilization Flocculate and agglomerate clay particles

by replacing monovalent cations such asNa+ with Ca++

Cement clay particles together by creatingCaCO3 from CaO plus atmospheric CO2 Cement clay particles together by creating

a pozzolanic reaction between CaO, SiO2,and Al2O3



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Clay Mineralogy

Source: hydram.epfl.ch/VICAIRE/mod_3/chapt_1/text.htm


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Clay Mineralogy


Kaolinite Illite Smectite


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10 - 300.2 - 2.00.05 - 0.2

Kaolinite

50 - 1000.2 - 2.00.01 - 0.1

Illite

200 - 8000.1 - 0.50.001 - 0.01

Montmorillonite

SpecificSurface(m2/g)

TypicalDiameter

(m)

TypicalThickness

(m)EdgeView


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Clay Mineralogy


Dispersed &Deflocculated

Dispersed &

Flocculated

Agglomerated &Flocculated

Agglomerated &Deflocculated


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Lime Stabilization Agglomerate clay particles by replacing

monovalent cations such as Na+ with Ca++

Cement clay particles together by creating

CaCO3 from CaO plus atmospheric CO2 Cement clay particles together by creating

a pozzolanic reaction between CaO, SiO2,

and Al2O3



9/23

A Bit of Chemistry

When limestone (calcium carbonate) isheated above 825C, carbon dioxide isdriven off, leaving lime (calcium oxide):

3 2825

heat

CCaCO CaO CO

> +

This process is called calcination.


10/23

A Bit of Chemistry

The lime is usually mixed with water toform slaked lime(calcium hydroxide)

2 2( )CaO H O Ca OH heat + +

which is more stable because the limesthirst for water has been slaked.


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A Bit of Chemistry

Carbon dioxide in the air can combinewith the slaked lime to essentially formnew limestone (calcium carbonate)

+ 22 3 2( )CO

Ca OH CaCO H O

This was a form of ancient cement.


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Lime Stabilization Agglomerate clay particles by replacing

monovalent cations such as Na+ with Ca++

Cement clay particles together by creating

CaCO3 from CaO plus atmospheric CO2 Cement clay particles together by creating

a pozzolanic reaction between CaO, SiO2,

and Al2O3



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Cement Hydration

+ + +CS H CSH CH heat

calcium silicate

water

calcium silicate hydrate gel

calcium hydroxide crystals


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Pozzalanic Reaction

+ + +CS H CSH CH heat

CH S CSH +

pozzolan


15/23

Treatment Selection


16/23

Unified Soil Classification System


17/23

Casagrandes Plasticity Chart


18/23

Selection Guide

Source: Army TM 5-822-14


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Selection Guide



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Selection Guide



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AASHTO Soil Classification


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Soil Modification Guide

Source: http://www.okladot.state.ok.us/materials/pdfs-ohdl/ohdl51.pdf


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Soil Stabilization Guide

Source: http://www.okladot.state.ok.us/materials/pdfs-ohdl/ohdl50.pdf

05 - soil stabilization

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