© 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
© 2014 Boise State University 2
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)
© 2014 Boise State University 3
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
© 2014 Boise State University 4
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
© 2014 Boise State University 5
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
© 2014 Boise State University 6
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
© 2014 Boise State University 7
➢ 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
© 2014 Boise State University 8
➢ 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.)
© 2014 Boise State University 9
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
© 2014 Boise State University 10
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
© 2014 Boise State University 11
✓ 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.)
© 2014 Boise State University 12
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
© 2014 Boise State University 13
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
© 2014 Boise State University 14
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 - - - - - - - - -
© 2014 Boise State University 15
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
© 2014 Boise State University 16
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
© 2014 Boise State University 17
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)
© 2014 Boise State University 18
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
© 2014 Boise State University 19
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
© 2014 Boise State University 20
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
© 2014 Boise State University 21
Task 5 : Establish Curing and Moisture Condition Protocols
➢ 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
© 2014 Boise State University 22
Task 5 : Establish Curing and Moisture Condition Protocols
➢ 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
© 2014 Boise State University 23
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
© 2014 Boise State University 24
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.
© 2014 Boise State University 25
Task 6 : Evaluating Long-term Durability of Stabilization
➢ 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
© 2014 Boise State University 26
Task 6 : Evaluating Long-term Durability of Stabilization
Cured /Moisture
Conditioned Sample
Alternate
Wetting/Drying
Leachate
Collection
Water
Leachate
Simultaneously
Proposed Durability Test Protocol procedures
© 2014 Boise State University 27
Task 6 : Evaluating Long-term Durability of Stabilization
➢ 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
© 2014 Boise State University 28
Task 6 : Evaluating Long-term Durability of Stabilization
➢ 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
© 2014 Boise State University 29
Task 6 : Evaluating Long-term Durability of Stabilization
➢ 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
© 2014 Boise State University 30
Task 6 : Evaluating Long-term Durability of Stabilization
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
© 2014 Boise State University 31
Task 6 : Evaluating Long-term Durability of Stabilization
➢ 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
© 2014 Boise State University 32
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
© 2014 Boise State University 33
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
© 2014 Boise State University 34
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
© 2014 Boise State University 35
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
© 2014 Boise State University 36
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
© 2014 Boise State University 37
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+
© 2014 Boise State University 38
THANK YOU
Questions/Discussion