OBG PRESENTS:

Advancements in In Situ Solidification/Stabilization for Environmental Remediation and Engineering ApplicationsRoy E. Wittenberg, PE | 2018 Environment Virginia Symposium

OBJECTIVESIntroduction to In Situ Stabilization/Solidification (ISS)

A brief history of the technology

Current state of the practice and implementation

Expanded applications using beneficial use materials

Current research initiatives

Future considerations

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TECHNOLOGY OVERVIEW

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Stabilization vs. Solidification

Stabilization/Solidification (S/S): Treatment technologies that prevent the migration of contaminants from contaminated media (i.e. soil, groundwater, sediment)

Stabilization: Chemical reaction to reduce leachability Immobilization Reduced Solubility

Solidification: Physical process binding/encapsulation Increase compressive strength Decreased permeability

In Situ Stabilization/Solidification

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In-place mechanical mixing of contaminated media with dry reagent or an injected engineered grout mixture

ISS

Portland Cement

Ground Granulated Blast Furnace Slag (GGBFS)

Cement Kiln Dust

Fly Ash

Bentonite

Organoclay

Lime

Potential Reagents

Common ISS applications utilize combinations of GGBFS, Portland Cement, and bentonite

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WHY? HOW DOES IT WORK?

The Romans had a word – Caementum, meaning to cut down in size. This had evolved from the early use of a mortar. Evolution of the term after the Roman times eventually brought forth today's "cement.“

Oldest found to date – lime concrete floor found during the construction of a road at Yiftah El in Galilee, Israel. 7000 BC.

Portland cement was first patented in 1824.

Defined as hydraulic cement consisting essentially of hydraulic calcium silicates, one or more of the forms of calcium sulfate as an interground addition.

A Brief History of Portland Cement

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The Hydration Process –Key to ISS

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Courtesy: Prof. Karen Scivener, EPFL

Cement

Water

Dissolution Precipitation

Crucial Compounds formed During the Hydration Process

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hydroxide calciumhydrate silicates CalciumwaterS)C(C silicates Calcium 23

+→++S

Two Important Categories of Supplementary Mineral Additives for Solidification

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Pozzolanic(i.e., low-calcium fly ash)

Cementitious(i.e., granulated iron blast-furnace slag)

Both pozzolanic and cementitious (i.e., high-calcium fly ash)

Hydration Mechanisms

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Both lead to denser cement matrices with lower permeability important for ISS sequestration of mobile contaminants

Portland cement is good for slag activation because it contains the three main chemical components that activate slag; lime, calcium sulfate and alkalies.

The pozzolanic reaction does not liberate large quantities of heat, and generally the reaction is slow, with appreciable reaction occurring only beyond 28 days. Calcium hydroxide serves as the activator

The Magic During In Situ Mixing

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Cementitious materials are prepared as a grout slurry

Slurry is mixed in situ using large diameter augers or other specialized mixing tools

Initially the grout is highly fluid and the mixing process emulsifies contaminated soil with the grout and particle size is greatly reduced

As hydration begins, fluidity is lost and cementitious materials bond together

Contaminated soil particles become encapsulated within the hardened matrix

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RELEVANCE AND CURRENT STATE OF THE PRACTICE

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Importance to the Power

Industry

Controlled engineering and cost competitive option vs. conventional excavation

Documented effectiveness on Organics (VOCs, SVOCs, PAHs, PCBs) and Inorganics (Metals, Radioactive Materials)

Reduction in short and long term liability

Community and Regulatory acceptance

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Current State of Practice

USEPA and State Agency Acceptance

USEPA : ISS is one of the most common in situ technologies used at CERCLA sites for source control (USEPA, 2010)

State: 26 States reported implementation of S/S technologies (ITRC, 2011)

MGP Sites: Currently being used to address impacted soil and groundwater across the U.S.

CCP Applications: Limited but have been used in specialized applications

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APPLICATIONS

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CURRENT APPLICATIONS

Vertical Rotary Mixed ISS – Crane Mounted Drill Table

Hydraulic Auger Mixed ISS – Delmag

Hydraulic Mixing Tool ISS – Allu/Lang Tool

Auger Mixed ISS

Hydraulic Mixing Tool ISS

Result: Solidified Monolith

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Design Process for Assessing ISS Performance Parameters

Identify specific design objectives

Establish the design parameters and criteria to meet those objectives

Identify mix designs for assessing both civil and remedial

objectives in bench test

Test for physical design parameters

to narrow down mix designs for performance of chemical testing

(leachability)

Select a mix design(s) for pilot

testing which meet both civil design

and remedial performance

objectives

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Design/Performance Parameters

Evaluate during bench and pilot scale testing

Volume Expansion (swell):

Evaluate during bench testing; pilot scale if required American Nuclear Society (ANS) 16.1 SPLP/TCLP not recommended

Leachability:

Evaluate during bench/pilot/full scale construction Common criteria: ≤ 1x10-6 to 1x10-8 (cm/sec)

Hydraulic Conductivity (Permeability):

Evaluated\ during bench/pilot/full scale construction Common criteria: ≥ 50 (psi)

Unconfined Compressive Strength (UCS):

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FUTURE APPLICATIONS

Barrier Technology for CCR Impoundments and Landfills

Sediment ISS

Applications for Coastal Resiliency

Barrier Technology for CCR Impoundments or Landfills

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ISS for Sediment

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Coastal Restoration and Resiliency

Potential Applications

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Levees

Seawalls

Shoreline Stabilization

Marine Habitat Restoration (e.g., concrete blocks artificial reefs)

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MARKET TRENDS AND FUTURE APPLICATIONS

Increasing GGBFS are Creating Demand for Alternative Binders

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0

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Cost

(Per

Sho

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Percent of Portland Cement Replaced With SDA

Percent SDA Replacement vs. Cost

$0

$10

$20

$30

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Portlland Cement Class F CCR SDA Blast Furnace Slag

Cost

(Per

Sho

rt T

on)

Cementitious Materials

Cost of Cementitious MaterialsAs levels of steel production have declined so has the availability of GGBFS

GGBFs increasingly imported from overseas markets

Consequently the cost for GGBFS is also increasing and approaching the cost for Portland cement

Alternative pozzolanic materials such as fly ash could provide an economically attractive alternative

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Some Current Research Initiatives

Combine two major “off-spec” materials consisting of Class F and spray dryer absorber ash (SDA) in percentages with Portland cement binder and admixtures

Create highly durable, sulfate resistant and dimensionally stable systems

Develop low-cost milling process for pre-processing of agglomerated “aged” CCR materials and impoundment CCR

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THE SOLUTION: Combine Class F and SDA to Create highly durable, sulfate resistant and dimensionally stable binder systems

THE CHALLENGE: Underutilization partially due to the difficulty of getting “off-spec” materials to meet ASTM standards for concrete

THE UNMET NEED: 177.3 million tons of CCR materials were produced in 2015—only 61.1 million tons were beneficially used, 116.3 million tons landfilled.

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SDA + Portland CementSulfate AttackDegradationFreeze/Thaw Failure

SDA + Class F + Portland CementHigh StrengthSulfate ResistantDurable

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Final Thoughts

New technologies and advanced research for beneficial use usher in a new era of previously untapped resources

Provides a doorway to more effectively “mine” these resources

Positive impact on reducing carbon emissions—reuse of resources and reduction in the use of Portland cement

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QUESTIONS

OBG PRESENTS:OBG | THERE’S A WAY

Thank you!Roy.Wittenberg@obg.com