GUIDELINES FOR STABILIZING PROBLEMATIC SOIL USING … · © 2014 Boise State University 1 GUIDELINES FOR STABILIZING PROBLEMATIC SOIL USING CALCIUM BASED STABILIZER Project PI: Bhaskar

© 2014 Boise State University 1

GUIDELINES FOR STABILIZING PROBLEMATIC

SOIL USING CALCIUM BASED STABILIZER

Project PI: Bhaskar Chittoori, Ph.D., PEAssistant Professor,

Civil Engineering Department,

Boise State University

Graduate Student

Amit Gajurel

Kick-Off Meeting


PI Background

➢ Bhaskar Chittoori, Ph.D., P.E.

➢ Education

✓ BS – 2002 ( JNTU, India)

✓ MS – 2004 (NITK, India)

✓ Ph.D. – 2008 (University of Texas at Arlington)

➢ Employment

✓ Field Engineer: 2004 – 2005 (India)

✓ Engineer II: 2009 – 2010 (Parsons and Brinkckerhoff – Dallas)

✓ Faculty Associate: 2010 – 2013 (University of Texas at Arlington)

✓ Assistant Professor: 2013 – Current (Boise State University)


Introduction

➢ Chemical Stabilization of soils

✓ Been around for about 70 years

✓ Serves a variety of purposes

✓ Agency specific guidelines

✓ Cost effective alternative – Subjective

➢ MDT

✓ Presence of high sulfate soils

✓ Lack of a way to compare costs between alternatives

✓ Limited experience with chemical stabilization

✓ No standardized practices across the state


Problem Statement

Chemical Stabilization of Problematic Soils within the State of Montana

Project Goals

Establish protocols for problematic

soils without soluble sulfates

Establish protocols for problematic

soils with soluble sulfates Laboratory

Tests

Effective Chemical

Stabilizer

Compare with

current alternatives

Life Cycle Cost

Analysis


Objectives

➢ Establish current state of practice with problematic soils

in Montana

➢ Determine the effectiveness of common soil stabilizing

agents for mitigating problematic Montana soils

➢ Develop protocols and specification for selection of

additive type and dosage

✓ Soils with sulfates

✓ Soils without sulfates

➢ Examine scope and impact of using stabilizing agents to

mitigate problematic soils against current MDT practice


Overview of Task Plan

Task 1: Current Practices Survey

Task 2: Material Selection

Task 3: Evaluate Chemical Stabilizers

Task 4: Establish Chemical and Mineralogical Changes in Mix Properties

Task 5: Establish Curing and Moisture Conditioning Protocols

Task 6: Evaluating Long-term Durability of Stabilization

Task 7: Life Cycle Cost Analysis

Task 8: Develop Guidelines and Protocols


➢ Literature Review of Practices – ND, SD,ID,WY and Canada (Saskatchewan region)

✓ Information on studies done for problematic soil stabilization

✓ Information on types of soil to be selected for Task 2

➢ Survey of practices – ND, SD,ID,WY and Canada (Saskatchewan region) state agencies

✓ Information on current practices of stabilized material –unpublished

✓ Information on current methods characterization of stabilized material

o Methods : Laboratory and Field

o Characterization : Chemical and Physical

Task 1 – Current Practices Survey


➢ Survey of practices – ND, SD,ID,WY and Canada

(Saskatchewan region) state agencies

✓ Information on design considerations of stabilized material

✓ Information on methods for accelerating curing and

moisture conditioning

✓ Input from TP – Review of Survey Questions

o Mid to late May

➢ Submission of Task 1 Report (Mid to late August)

Task 1 – Current Practices Survey (Cont.)












Task 2 – Material Selection

➢ Locating problematic areas using GIS maps

➢ Development of questionnaire

✓ Understand extent of problem

✓ Locate beneficiary districts

✓ Understand performance of full/experimental scale sections-if any

✓ Input from TP – assist in development of questionnaire

➢ Site selection/Sampling location

✓ Expected Soils (Preliminary)

o 3 – High PI clays w/wo excessive sulfates

o 2 - Low plastic clays

o 1 – Sandy subgrade


✓ Site selection

o Upcoming construction site

o Input from TP – Site acceptable to TP

✓ Sampling location

o Input from TP – Discussion with TP

✓ Sample excavation and collection

o MDT – 200-300 lb. per site

o Top few feet

o No top soil / organics

o Collection in one central location

✓ Sample pick-up from cenral location by BSU personnel

Task 2 – Material Selection (Cont.)


Task 2 – Material Selection (Cont.)

➢ Additives

✓ Laboratory grade Chemicals

o Cement

o Lime

o Fly ash

➢ Task report – Merged with task 3

✓ Will submit a separate report on request at the end of this

task












Task 3 – Evaluate Chemical Stabilizers

➢ Main Goal : Determination of best additives among the

three for each of the soil samples.

➢ Establish matrix of additives types/amount for different

soils

✓ Aids in development of stabilizer selection guideline

Soil\AdditivesCement Lime Fly ash

2% 4% 6% 6% 8% 10% 6% 8% 10%

1 - - - - - - - - -

2 - - - - - - - - -

3 - - - - - - - - -


Task 3 – Evaluate Chemical Stabilizers (Cont.)

➢ Tests proposed

✓ Index Test – Gradation, PI and Soil Classification

✓ Strength and compressibility tests

✓ Chemical and Mineralogical analysis – Task 4

✓ Assessment of curing methods– Task 5

✓ Assessment of permanency of Chemical Stabilization – Task 6

➢ Submission of Task 2 & Task 3 Report












Task 4 : Chemical and Mineralogical Analysis

➢ Main Goal : Evaluation of Clay mineralogy & amount of

reactive silica/alumina and sulfate

➢ Performed for control (untreated) and chemically treated

soils – establish chemical and mineralogical changes

➢ Procedures:

✓ Determination of soluble sulfate as per AASTHO procedure

o Modification to avoid platinum crucible

o Alternative procedure shall be used in case of low soluble sulfate

✓ Determination of reactive alumina and silica as per Puppala

et. al. (2005) and Wattanasanticharoen et. al. (2005)


Task 4 : Chemical and Mineralogical Analysis (Cont.)

✓ Determination of dominating clay mineral as per Chittoori

and Puppala (2011)

o Verification of formation of pozzolanic compounds – responsible

for improvement of Soil.

➢ Submission of Task 4 Report












Task 5 : Establish Curing and Moisture Condition Protocols

➢ Main Goals

✓ Determine appropriate concentration of Additive

o Triaxial or unconfined compressive strength test (UCS)

o Modulus tests

✓ Establish curing and moisture conditioning protocols

o Represents Montana field conditions

o Less time consuming

Problematic Soil

Treated Soil

Treatment as per matrix

Curing and Moisture

Conditioning

Triaxial/UCS

Verify requirements



➢ Curing

✓ Higher Temperature

o Increase lime-soil reaction

o Early commencement of

pozzolanic activity

✓ Issue will be addressed by

factorial design

o Curing at temperature =

f(additive) and 72oF

o Curing at full moisture

with/without membrane

Moisture

RegimeTemperature

Strength of Stabilized

material

Curing



➢ Moisture Conditioning Techniques

✓ Back Pressure Saturation

o Triaxial Setup

o Water is pushed into the specimen when σi > σd

o Amount of flow/saturation time = f (σd , σi – σd)

o σi > σd shall be determined considering

▪ Time of saturation

▪ Damage to the specimen due to hydraulic gradient

▪ Saturation in field condition

✓ Submerging Specimen

o Not applicable to all materials

▪ Harshly condition coarse grained

▪ Not effectively condition low permeability materials

σd

σd

σd σd

σi

σd σd

σi












Task 6 : Evaluating Long-term Durability of Stabilization

➢ Main goal: Study Permanency of Chemical Treatment

➢ Develop protocols for treated soil undergoing wet/ dry

cycles and leachate for conditions close to Montana’s

condition.

➢ Develop protocols for treated soil undergoing

Freeze/Thaw cycles for conditions close to Montana’s

condition.



➢ Durability Studies – Wetting/Drying and leachate

Cured /Moisture

Conditioned Sample

Alternate

Wetting/Drying

Cured /Moisture

Conditioned Sample

Leachate

Collection

1

2

Water

Leachate

Typical Durability Test Procedures



Cured /Moisture

Conditioned Sample

Alternate

Wetting/Drying

Leachate

Collection

Water

Leachate

Simultaneously

Proposed Durability Test Protocol procedures



➢ Wet/dry or Freeze/Thaw and leachate study on same sample

✓ Simulates field condition

✓ Understand the effect of presence of water on chemically

stabilized soil

✓ Address permanency of chemical stabilization

o Rainfall

o Ground water flow

o Moisture migration



➢ Moisture flow

✓ Water tank

✓ Constant Pressure

➢ Leachate Collected after each cycle ( 1 pore volume)

✓ pH

✓ Free Calcium, alumina and sulfate

✓ Statistical analysis to access loss of stabilizers

➢ Correlate leaching cycles with field moisture movement due to rainfall

➢ Develop reliable procedure for addressing

✓ Leaching

✓ Permanency of chemical stabilization

Water

Leachate



➢ Durability Studies – Freeze/Thaw

✓ Volume change

✓ Soil Strength and Stiffness determined

o Insight of seasonal moisture fluctuation on soil property

✓ Procedure modified to match Montana’s condition and time taken to run test

➢ Suggestions and input from TP on protocols –for:

✓ Freeze and thaw

✓ Wet/dry and leachate



Follow protocol developed

Chemically Stabilized

Soil

Run durability test

Varying number of

cycles

Volume & moisture Strength – UCS testMineralogical - XRD

each cycle

Data AnalysisChange in soil properties

due to

• Wet/dry cycles

• Freeze/thaw cycles

• Stabilizer reaction -

variation of XRD data



➢ Output :

✓ Assessment of only chemical stabilizer’s durability

performance

o The effect of moisture leaching and seasonal moisture fluctuation

is subtracted

➢ Submission of Task 5 & Task 6 report












Task 7 : Life Cycle Cost Analysis(LCCA)

➢ Help make informed decision on selection of appropriate

design alternative

➢ Submission of Task 7

LCCA

Current MDT

PracticeChemical Stabilization

LCCA using NCHRP Guideline












Task 8 : Development of Guideline and Protocols

➢ Preliminary protocol for lab testing is developed after

✓ Completion of Task 1-Task 6

✓ Review of the performance of existing site

➢ Interaction and Input from TP

✓ Evaluate practicality and validity

✓ Consideration of institutional aspect

➢ Incorporation of modification from TP


Task 8 : Development of Guideline and Protocols

➢ The guideline shall include

✓ Appropriate type and concentration of additives given the

type and environmental condition of the site

✓ Ideal and retained strengths and moduli

✓ Chemical and mineralogical properties of the mix

✓ Long-term durability in terms of moisture susceptibility, and

retention of stabilizers

➢ Submission of final report


Project Time Line

Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun July Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun July Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun

15%

5%

10%

10%

20%

20%

10%

10%

FY 2017 FY 2018 FY 2019Research Activity

Task 2

Task 1 Current Practice Survey+

Estimated % of

Total Project

Budget

Establish Curing and

Moisture Conditioning

Protocols*

Material Selection *

Evalaute Chemical

Stabilizers*+Task 3

Task 4

Kick-off Meeting

*Expected travel/meeting+Deliverable

Task 5

Establish Chemical and

Mineralogical Changes in

Mix Properties*

Task 6

Task 8

Long-Term Durability

Studies+

Develop Guidelines and

Protocols*+

Task 7 Life Cycle Cost Analysis+


THANK YOU

Questions/Discussion

Documents

GUIDELINES FOR STABILIZING PROBLEMATIC SOIL USING … · © 2014 Boise State University 1 GUIDELINES FOR STABILIZING PROBLEMATIC SOIL USING CALCIUM BASED STABILIZER Project PI: Bhaskar