Mahoney-Aggregates Containing Pyrrhotite€¦ · •Three Rivers, Quebec -Using 0.23% by volume...
Transcript of Mahoney-Aggregates Containing Pyrrhotite€¦ · •Three Rivers, Quebec -Using 0.23% by volume...
Aggregates Containing Pyrrhotite
James Mahoney
Executive Director
Connecticut Transportation Institute
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
Image Courtesy of Advance Testing
Microscopic Damage from Pyrrhotite in Concrete
Image Courtesy of Advance Testing
Ettringite in Cracks
Image Courtesy of Advance Testing
Ettringite Formation in Concrete Void Space Caused By Pyrrhotite Oxidation
Image Courtesy of Advance Testing
Concrete Core without Pyrrhotite
Image Courtesy of Advance Testing
Pyrrhotite in Impacts on Concrete
Image Courtesy of Advance Testing
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
Courtesy Wille and Zhong
Concrete Damage
Courtesy Wille and Zhong
Concrete Damage
Courtesy Wille and Zhong
Concrete Damage
Courtesy Wille and Zhong
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