mahoney-aggregates containing pyrrhotite€¦ · •three rivers, quebec -using 0.23% by volume...

Aggregates Containing Pyrrhotite

James Mahoney

Executive Director

Connecticut Transportation Institute

[email protected]

Pyrrhotite Damage is a Slow Motion Disaster

•Not a photogenic disaster

•Damage occurs slowly

•Driving by houses – nothing looks out of place

•Houses slowly become unsafe

• Swelling concrete wracks the house and concrete foundation becomes unstable

What is Pyrrhotite?

• Pyrrhotite is an iron sulfide mineral

• Closely related to other iron sulfide minerals:

• Pyrite

•Marcasite

• All of these minerals have a desire to oxidize in the presence of oxygen and water

Pyrrhotite is an unusual mineral

• Fe(1-x)S where x=0 → 0.2• Typical combinations Fe7S8, Fe9S10, Fe10S11, or Fe11S12

• Pyrite is FeS2

• May be “contaminated” with Copper, Nickel or Cobalt• Has different crystaline structures• Has variable degrees of stability based on structure

• May or may not be magnetic• Is responsible for the weak magnetic fields observed by

spacecraft orbiting Mars

Pyrrhotite Oxidation• Exothermic reaction (releases heat)

•Has been blamed for starting mine fires when large quantities of pyrrhotite are first exposed to air and

• Iron sulfides in rock waste has been blamed for acidification of water runoff

• Iron sulfides can be used to make sulfuric acid

Products of Iron Sulfide oxidation in Concrete

•When iron sulfides oxidize it produces iron oxides and sulfuric acid

• Iron oxides occupy more space than original molecules

• Sulfuric acid attacks the concrete paste weakening it and it forms secondary expansive minerals such as ettringite

• Bottom line: the concrete is weakened with internal stresses growing from the swelling materials in the concrete

Why Does Pyrrhotite Matter?

Kent

Sharon

StaffordSalisbury

Lebanon

LymeNewtown

Norfolk

Litchfield

Killingly

Goshen

Guilford

Granby Woodstock

Haddam

Suffield

Tolland

New Milford

Cornwall

Danbury

Hebron

Ashford

Pomfret

Union

Ledyard

Enfield

Montville

Oxford

Mansfield

Salem

Colchester

Thompson

Groton

Plainfield

Greenwich

Avon

Berlin

Canaan

Madison

East Haddam

Glastonbury

Coventry

Griswold

Easton

Shelton

Stamford

Wilton

Preston

Bristol

Hamden

Hartland

Ellington

Redding

Southbury

Torrington

Somers

Cheshire

Windsor

Voluntown

Middletown

Warren

Fairfield

Simsbury

Canterbury

WoodburyNorwich

Stonington

Canton

Wallingford

Eastford

Monroe

Ridgefield

Sterling

East LymeWaterford

Willington

Colebrook

Brooklyn

Washington

North Stonington

Roxbury

Milford

Winchester

Southington

Harwinton

Durham

Killingworth

Meriden

Barkhamsted

Windham

Burlington

Morris

Portland

Bozrah

New Hartford

Hampton

Waterbury

Wolcott

Weston

Norwalk

Watertown

East Hampton

Trumbull

Putnam

Sherman

Chaplin

Bethel

Bethany

Lisbon

Old Lyme

Farmington

Vernon

Branford

Bloomfield

Manchester

Franklin

Orange

Columbia

Plymouth

Clinton

Bolton

Chester

Scotland

Westport

Hartford

East Windsor

Essex

Brookfield

South Windsor

New Fairfield

Darien

Andover

MarlboroughBethlehem

New Canaan

New Haven

North HavenSeymour

Middlebury

Sprague

Prospect

Woodbridge

Naugatuck

Westbrook

East Granby

North Canaan

East Hartford

Rocky Hill

Cromwell

Deep River

Plainville

Wethersfield

Ansonia

Stratford

North Branford

West Hartford

Bridgeport

Bridgewater

Newington

Middlefield

Old Saybrook

New Britain

East Haven

Thomaston

West Haven

Derby

Beacon Falls

Windsor Locks

New London

§̈¦95

§̈¦84

§̈¦395

§̈¦91

§̈¦384

§̈¦291

§̈¦691

§̈¦684

£¤44

£¤7

£¤5

SV15

SV8

SV9

SV2

Explanation

2014_2015_Active_Quarries

Rocks containing Pyrrhotite

Rocks containing Pyrite

4 0 42 Miles

1:250,000

Bedrock Geological Map of Connecticut Connecticut Geological and Natural History Survey

Natural Resources Atlas Series. 2 sheets, 1:125,000 (Rodgers, 1985)

Connecticut Geological SurveyDepartment of Energy and Environmental Protection

www.ct.gov/deep/geology

Connecticut Geologic Units containing Pyrrhotiteand

Active Bedrock Quarries

Where is Pyrrhotite in Connecticut?

Connecticut Background History• Residential poured Concrete foundations began to

develop unusual cracking (spider/map) in the 1990’s from 1980’s placements• After enough houses were identified with this cracking,

the common thread was determined to be a single concrete supplier/quarry• The cause of the cracking was unknown although the

cracking resembled ASR• A meeting was held with Connecticut officials from

multiple departments in 2002-3 timeframe to discuss the problem•Nothing came of the meeting

CT History Continued• As time progressed, more and more affected homeowners came

forward and in 2015 the Department of Consumer Protection and Attorney General Launched investigation into the cause of the cracking to determine if consumer protection laws were violated

• Concrete supplier continued to provide concrete using the same quarry materials until Companies signed a voluntary agreement to stop selling materials for residential concrete in May 2016

• Research by Wille and Zhong in 2016 showed pyrrhotite in the quarry aggregate is a factor in the concrete degradation

• Concrete supplier has maintained throughout that the problem is with the installation such as additional water added by installers

CT History Continued

• Concrete supplier also produced septic tanks and other precast drainage products

• Septic tanks are also failing and being replaced

• 20 Bills were introduced during the 2017 Legislative Session and zero were passed

• CT still does not have a budget and some of the proposed legislation may be in budget bill when that is finalized

CT House Foundations• Approximately 600 homeowners have registered with the

Department of Consumer Protection as having the problem

• Currently, the only recognized remediation is to remove and replace the concrete foundation

• It is estimated that more than 34,000 CT residences contain concrete from this supplier

• No records from the supplier exist to determine exactly how many residences may be affected

• 2016 CT law was enacted to require recording concrete supplier as part of Certificate of Occupany

• Supplier also provided concrete across the border to Massachusetts

Map of affected Towns – Courtesy of Capital Region Council of Governments (11-29-2016)

Kent

Sharon

Stafford

Killingly

NorfolkSalisbury

Litchfield

Newtown

Lebanon

Lyme

Guilford

Goshen

Suffield

Tolland

Granby Woodstock

Haddam

New Milford

Cornwall

Danbury

Pomfret

Ashford

Hebron

Union

Montville

Enfield

OxfordLedyard

Mansfield

Plainfield

Berlin

Groton

Salem

Colchester

Avon

Thompson

Greenwich

Wilton

Madison

GlastonburyBristol

Coventry

Griswold

Canaan

Stamford

Shelton

East Haddam

Preston

Easton

Hartland

Torrington

Ellington

Hamden

Southbury

Redding

Voluntown

Fairfield

Windsor

Warren

Middletown

Somers

Cheshire

Simsbury

Canterbury

Norwich

Wallingford

Woodbury

Sterling

Stonington

Eastford

Ridgefield

Waterford

Canton

Willington

Monroe

Brooklyn

Milford

East Lyme

Washington

North Stonington

Colebrook

Roxbury

Killingworth

Harwinton

Southington

Winchester

Burlington

Morris

Durham

Portland

Meriden

Windham

Barkhamsted

New Hartford

Bozrah

Wolcott

Waterbury

Norwalk

Hampton

Watertown

Trumbull

Weston

Bethel

Putnam

Bethany

Chaplin

Sherman

Vernon

Farmington

Lisbon

Bloomfield

Franklin

Old Lyme

Plymouth

Manchester

Orange

Bolton

Clinton

Columbia

Hartford

Westport

Scotland

Chester

Brookfield

East Windsor

South Windsor

Essex

Darien

Andover

Bethlehem

Seymour

Prospect

Sprague

Naugatuck

North Canaan

Cromwell

Rocky Hill

Deep River

East Hampton

Branford

Stratford

New Fairfield

Marlborough

North Branford

New Canaan

Middlebury

North Haven

New Haven

West Hartford

Woodbridge

Bridgeport

Westbrook

Bridgewater

East Hartford

East Granby

Newington

Middlefield

New Britain

Old Saybrook

Plainville

East Haven

Thomaston

Wethersfield

Derby

West Haven

Ansonia

Beacon Falls

Windsor Locks

New London

!

0 10 205Miles

Reported Incidents

Very High

High

Medium

Low

30+10 - 29

3 - 9< 3

Data compiled from Town Assessors, Connecticut Department of Consumer Protection, and the Connecticut Insurance Department. Map updated November 29th, 2016.

CT Impacts

• Exact number of impacted houses is not known

• 10 Year Statute of Limitation on concrete foundations

• Generally taking more than 10 years to show damage

• Most homeowners insurance companies are denying coverage for this damage

• Concrete work is typically in the $150,000 - $200,000 per house (not including damage to hardscape, landscape, relocation, etc)

• Condominiums are also part of this problem and are much more complicated

• Currently there is no financial relief for homeowners

Impacts to CT• CT real estate market in the region is significantly

impacted

•Houses showing damage are virtually worthless

•Home buyers are requesting core testing and if any pyrrhotite is detected, buyers are either walking away or significantly negotiating the price downward

•Most towns are reducing the assessed values of houses showing damage

• Some towns are waiving building permit fees for repairing foundations

CT Pyrrhotite Problem is Growing

• Concrete placed from 1983 – most likely through 2015 impacted

• Commercial properties are now reporting problems

•Municipal buildings as well are reporting issues

• Elementary school

• Fire House

• First bridge (municipal) is potentially showing signs of the problem

• Rough estimates to repair all of the damage are in the $billions

Concrete Without Ettringite Deposits or Cracking

Image Courtesy of Advance Testing

Microscopic View of Pyrrhotite in Concrete


Microscopic Damage from Pyrrhotite in Concrete


Ettringite in Cracks


Ettringite Formation in Concrete Void Space Caused By Pyrrhotite Oxidation


Concrete Core without Pyrrhotite


Pyrrhotite in Impacts on Concrete


Core With Large Piece of Pyrrhotite

Core with Visible Cracking From Aggregate Particle

Aggregate Rusting and Popping Out of Concrete

Damage to Concrete Foundations

Courtesy Wille and Zhong

Concrete Foundation Damage


Concrete Damage


Where Else Has This Problem Occurred?• Three Rivers, Quebec - Using 0.23% by volume pyrrhotite

threshold

• Oslo, Norway

• Spain

• Cornwall, England – Mundic Blocks

• Houses built from 1900-1950’s using blocks with mine waste as aggregate

• (Mundic is an old Cornish word for iron pyrites)

• Developed a risk based system for insurance and mortgage purposes

NYSDOT Aggregate Specifications

•Only specification found in the region regarding pyrrhotite

• Limited to 1% iron sulfides in aggregates

Is It Possible to Develop a Fast and Low Cost Test for Pyrrhotite in Lieu of Petrographic Analysis?

•Navy’s SBIR Program is funding research to develop a handheld unit to test aggregate as well as in hardened concrete

• Spectroscopy shows promise for developing a test method

• Including X-Ray Fluorescence and X-Ray Diffraction

• Critical step in determining an estimate number of affected houses based on data driven decisions

Failed Remediation Efforts

•Epoxy sealing of cracks

•Poured foundation inside of the original foundation

•Swelling concrete destroyed new wall

•Piles driven under the foundation to support it

•Steel reinforcement with tiebars

•Plenty of ideas are out there from both well intentioned and not-so well intentioned people

There Are Many More Questions Than Answers

• Can a threshold level of pyrrhotite be established below which damage may not occur?

• How many samples need to be taken to properly characterize the pyrrhotite level in a foundation?

• Can steps be taken for foundations not showing damage to prevent any further damage?

• For structurally sound foundations with minor cracking, is it possible to remediate it without full foundation replacement?

• Are threshold values from Canada applicable to Connecticut?

• Are there other factors such are other minerals that affect the rate of damage to concrete?

Thank You - Questions

mahoney-aggregates containing pyrrhotite€¦ · •three rivers, quebec -using 0.23% by volume...

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