Is your foundation compromised by pyrrhotite?

Since 2013, Sedexlab provides coring and laboratory services to property owners concerned with the possible presence of the mineral pyrrhotite in their concrete foundation.  Sedexlab is a leading laboratory and expert involved in the crumbling foundations crisis having performed testing on more than 1400 concrete core samples extracted from foundations at risk with deterioration related to pyrrhotite-bearing aggregate in Canada, Connecticut and Massachusetts.

Sedexlab employs petrographers with extensive experience in petrographic examinations of concrete and aggregate and who are specially trained to identify and quantify pyrrhotite in coarse aggregate particles.

All petrographers are licensed professional geologists skilled in mineralogy, optical minerology and concrete petrography.   Sedexlab complies with ASTM and CSA standards along with other national and international standards.

WHO NEEDS THE CONCRETE CORE ANALYSIS?

  • Homes, businesses, additions, detached garages built between 1983 and 2015 in northeastern Connecticut and south-central Massachusetts.
  • Property owners noticing damages to their foundation and who want to know if pyrrhotite-induced expansion is the cause.
  • Property owners looking to sell and who are requiring testing to prepare for potential buyers
  • Potential property buyers who are concerned about pyrrhotite issues asking for foundation testing before a property transaction.
  • Property owners looking to reduce property taxes.
  • Connecticut home owners filing claims for foundation replacement to the Connecticut Foundation Solutions Indemnity Company (CFSIC).
Our Costs
$1950.00 US

Includes

Extraction of two (2) concrete core samples and shipment to our lab*

+

Laboratory analysis of two (2) concrete core samples**

All costs are eligible for the CRCOG testing reimbursement program.

 

Turnaround time for the submission of our report:

2-3 weeks

(after receiving the samples)

Schedule coring

 

*Fees for each additional core extraction are $125.00 US (sample shipment included)

**Fees for each additional core laboratory analysis are $500.00 US

What you obtain

A written report signed by a Certified Professional Geologist describing:

  • Petrographic analysis conducted in accordance with ASTM C 856 ‘’Standard Practice for Petrographic Examination of Hardened Concrete’’.
  • Determination of presence or absence of pyrrhotite in coarse aggregate using microscopic examinations on polished concrete sections.
  • Percentage of pyrrhotite in coarse aggregate expressed in weight and in volume.
  • Percentage of potentially reactive aggregates using stereomicroscopy and polarized microscopy.
  • Percentage of sulfur per unit mass of coarse aggregate (0.1% European standard threshold limit when pyrrhotite is present).
  • Physical analysis (concrete density and porosity measurements).
  • Synthesis of petrographic, sulfur and physical analysis results.
  • Concluding statements with professional judgement.
  • Petrographic photographs of concrete sections analyzed.
  • Site photographs and summary of existing concrete conditions.

Our Work Process

We have established strong partnerships with local engineering firms who perform all core drilling, sample identification and packaging as well as sample shipments. Typically, we will send a team of technicians to your property within 2-3 business days.

• A minimum of two (2) core samples shall be collected and submitted for analysis.
• Core samples shall be extracted from different foundation walls of the tested building.
• Core samples shall be labeled and fully documented regarding location of sample collection from concrete foundation with control number matching written report.
• Cores shall be drilled out of a 4 inch diameter cylinder.
• Coring shall be executed all the way through the wall in order to confirm presence or absence of moisture barriers.
• Resulting cavities will be filled with non-shrink grout.
• Reasonable access must be provided. Example: Moving furniture / home decor / rugs is the responsibility of the homeowner or client.
• Usual delivery time to our lab is 3 business days.

Existing concrete conditions will be reported through a questionnaire submitted to and completed by the client with the assistance of a structural engineer or an ACI-certified Concrete Field Technician. Clearly labeled site photographs of core locations, observed damages and other relevant property elements will be taken to support observations noted to the questionnaire. Summary of existing concrete conditions and site photographs are attached to the Concrete Core Analysis report.

Sedexlab petrographers use stereomicroscopy and polarized light microscopy to perform the mineralogical assessment of aggregates in concrete which allows highlighting potential problems related to expansive reactions due to the oxidation of pyrrhotite and other iron-sulfide minerals in rock aggregates. Petrographic examinations are conducted in accordance with relevant guidelines outlined in ASTM C 856-17, “Standard Practice for Petrographic Examination of Hardened Concrete.”

The Analysis includes:

• Determination of percentage of coarse aggregate particles containing pyrrhotite.
• Determination of percentage of coarse aggregate particles with high potential reactivity.
• Determination of percentage of pyrrhotite per unit mass and per unit volume of coarse aggregate
• Determination of evidence of oxidation of pyrrhotite (presence of replacement iron oxides).
• Detailed concrete core description (concrete condition, coarse and fine aggregate description, steel reinforcement description, moisture barriers description)
• Petrographic composition of coarse aggregate and fine aggregate
• Composition of iron sulfide minerals in the coarse aggregate (pyrite, pyrrhotite, chalcopyrite, etc.).
• Petrographic photographs of concrete sections analyzed.

Since pyrrhotite is a sulfide mineral composed of iron (Fe) and sulfur (S), measuring sulfur content in concrete and coarse aggregate is an important part of the Concrete Core Analysis and supports observations made during microscopic examinations. European and Canadian standards for concrete coarse aggregate have placed a limit of 0.1% sulfur if pyrrhotite is identified in the coarse aggregate.

Total sulfur content in concrete is performed using LECO infrared combustion sulfur analysis on a portion of each core sample in the as-received condition.

The Analysis includes:

• Determination of average percentage sulfur per unit mass of concrete.
• Determination of percentage sulfur per unit mass of coarse aggregate.
• Values obtained are compared against the 0.1% European EN-12 620 (2003) and Canadian CSA A23.1 (2014) standards for coarse aggregate.

Physical properties of concrete are influenced by its density as it generally reflects concrete strength and durability as well as the amount of air voids and porosity.

Concrete density and porosity measurements are conducted on a portion of the core sample in the as-received condition in accordance with the relevant guidelines outlined in ASTM C642 ‘’Standard Test Method for Density, Absorption, and Voids in Hardened Concrete’’.

The Analysis includes:

• Determination of Concrete Density (lb/ft³)
• Determination of absorption after immersion (%) and after immersion and boiling (%)
• Determination of volume of permeable voids (%)
• Values obtained are compared against values generally accepted for normal resistance concrete used in building foundations.

The written summary report comes complete with a synthesis of petrographic, sulfur and physical analysis results as well as concluding statements with professional judgement. The report clearly states that conclusions expressed are based on the assumption that the sampled cores are representative of the foundation’s general condition. Test results/final reports are sent by email to the Client. A hard copy of such results and reports can be provided upon request for an additional $10.00 fee.

We have established strong partnerships with local engineering firms who perform all core drilling, sample identification and packaging as well as sample shipments. Typically, we will send a team of technicians to your property within 2-3 business days.

• A minimum of two (2) core samples shall be collected and submitted for analysis.
• Core samples shall be extracted from different foundation walls of the tested building.
• Core samples shall be labeled and fully documented regarding location of sample collection from concrete foundation with control number matching written report.
• Cores shall be drilled out of a 4 inch diameter cylinder.
• Coring shall be executed all the way through the wall in order to confirm presence or absence of moisture barriers.
• Resulting cavities will be filled with non-shrink grout.
• Reasonable access must be provided. Example: Moving furniture / home decor / rugs is the responsibility of the homeowner or client.
• Usual delivery time to our lab is 3 business days.

Existing concrete conditions will be reported through a questionnaire submitted to and completed by the client with the assistance of a structural engineer or an ACI-certified Concrete Field Technician. Clearly labeled site photographs of core locations, observed damages and other relevant property elements will be taken to support observations noted to the questionnaire. Summary of existing concrete conditions and site photographs are attached to the Concrete Core Analysis report.

Sedexlab petrographers use stereomicroscopy and polarized light microscopy to perform the mineralogical assessment of aggregates in concrete which allows highlighting potential problems related to expansive reactions due to the oxidation of pyrrhotite and other iron-sulfide minerals in rock aggregates. Petrographic examinations are conducted in accordance with relevant guidelines outlined in ASTM C 856-17, “Standard Practice for Petrographic Examination of Hardened Concrete.”

The Analysis includes:

• Determination of percentage of coarse aggregate particles containing pyrrhotite.
• Determination of percentage of coarse aggregate particles with high potential reactivity.
• Determination of percentage of pyrrhotite per unit mass and per unit volume of coarse aggregate
• Determination of evidence of oxidation of pyrrhotite (presence of replacement iron oxides).
• Detailed concrete core description (concrete condition, coarse and fine aggregate description, steel reinforcement description, moisture barriers description)
• Petrographic composition of coarse aggregate and fine aggregate
• Composition of iron sulfide minerals in the coarse aggregate (pyrite, pyrrhotite, chalcopyrite, etc.).
• Petrographic photographs of concrete sections analyzed.

Since pyrrhotite is a sulfide mineral composed of iron (Fe) and sulfur (S), measuring sulfur content in concrete and coarse aggregate is an important part of the Concrete Core Analysis and supports observations made during microscopic examinations. European and Canadian standards for concrete coarse aggregate have placed a limit of 0.1% sulfur if pyrrhotite is identified in the coarse aggregate.

Total sulfur content in concrete is performed using LECO infrared combustion sulfur analysis on a portion of each core sample in the as-received condition.

The Analysis includes:

• Determination of average percentage sulfur per unit mass of concrete.
• Determination of percentage sulfur per unit mass of coarse aggregate.
• Values obtained are compared against the 0.1% European EN-12 620 (2003) and Canadian CSA A23.1 (2014) standards for coarse aggregate.

Physical properties of concrete are influenced by its density as it generally reflects concrete strength and durability as well as the amount of air voids and porosity.

Concrete density and porosity measurements are conducted on a portion of the core sample in the as-received condition in accordance with the relevant guidelines outlined in ASTM C642 ‘’Standard Test Method for Density, Absorption, and Voids in Hardened Concrete’’.

The Analysis includes:

• Determination of Concrete Density (lb/ft³)
• Determination of absorption after immersion (%) and after immersion and boiling (%)
• Determination of volume of permeable voids (%)
• Values obtained are compared against values generally accepted for normal resistance concrete used in building foundations.

The written summary report comes complete with a synthesis of petrographic, sulfur and physical analysis results as well as concluding statements with professional judgement. The report clearly states that conclusions expressed are based on the assumption that the sampled cores are representative of the foundation’s general condition. Test results/final reports are sent by email to the Client. A hard copy of such results and reports can be provided upon request for an additional $10.00 fee.

Background

Pyrrhotite, a naturally occurring iron sulfide found in rock aggregate, is the suspected cause of the failing concrete foundations problem in Connecticut and Massachusetts. These foundations are experiencing a slow crack development, resulting in the eventual loss of concrete strength. The problems, sometimes developing within the first 10 years, often begin to appear after 15 to 20 years or more. According to the Geological Society of America, rock aggregate in these failing concrete foundations was largely mined from a single quarry in Willington (CT), within a stratified metamorphic unit mapped as Ordovician Brimfield Schist.

Pyrrhotite particles in coarse aggregates are unstable in oxidizing conditions. When exposed to water and oxygen, pyrrhotite oxidizes to form acidic-, iron-, and sulfate-rich by-products. One of these products is sulfuric acid which attacks the cement paste, weakening it, and generating sulfates as a by-product. These sulfates react with portlandite and hydrated aluminate phases in the paste, resulting in an expansion in the form of secondary minerals of greater volume. With more expansion and cracking occurring, more moisture is allowed in the concrete, exposing more pyrrhotite, and consequently increasing the rate of distress. At present no measure other than foundation replacement is known to reverse or eliminate pyrrhotite-Induced concrete deterioration.

According to the state Department of Housing, 42 towns and upwards of 35,000 homes in Connecticut could be potentially affected, primarily in the northeastern portion of the State. Single-family homes, home additions and detached garages, condominiums and other buildings are affected. Just north of the border, significant parts of south western Massachusetts could also be potentially affected although no precise numbers have been issued.

The problematic concrete allegedly originated from a single Stafford Springs (CT) concrete producer during the years 1983 – 2015. The company reportedly used reactive pyrrhotite-bearing rock aggregate from a quarry located in Willington (CT) for the fabrication of concrete for building foundations.

The main tell-tale signs of premature foundation deterioration caused by pyrrhotite-induced expansive reactions in concrete are: Map/web-like cracking patterns, horizontal cracking, spalling on surface of concrete, foundation walls bowing, rust-like discoloration on surface of concrete, white efflorescence (powder) in the vicinity of cracking surface. Cracks can rapidly evolve until the eventual loss of concrete strength.

Pyrrhotite Content

Although the undesirable nature of pyrrhotite for the manufacture of concrete is recognized and although contents as low as 0.3% pyrrhotite by mass of coarse aggregate have reportedly caused significant concrete distress (e.g., in Trois-Rivières, Canada), no precise value has been issued in any U.S. State or Federal laws, as to the maximum authorized pyrrhotite content in coarse aggregates for use in concrete. More research and case history data are needed to reveal with more accuracy the minimum level at which significant concrete deterioration will occur.

Sulfur Content

The European standard for coarse aggregate NF EN 12620 (article 6.3.2), in force since 2003, has placed a limit of 0.1% sulfur if pyrrhotite is identified in the coarse aggregate. In Canada, CSA A23.1 (R2014) states that aggregate susceptible to cause excessive expansion of the concrete due to the presence of sulfides (pyrite, pyrrhotite, marcasite) should not be used in concrete. In addition, this standard recommends not using aggregates containing pyrrhotite in new concrete if these aggregates bear sulfur content higher than 0.1%. The US Army Corps of Engineers recent recommendations state that aggregate for use in new concrete should be assumed pyrrhotite-bearing and should be accepted only if its sulfur content is below 0.1%.

Pyrrhotite, a naturally occurring iron sulfide found in rock aggregate, is the suspected cause of the failing concrete foundations problem in Connecticut and Massachusetts. These foundations are experiencing a slow crack development, resulting in the eventual loss of concrete strength. The problems, sometimes developing within the first 10 years, often begin to appear after 15 to 20 years or more. According to the Geological Society of America, rock aggregate in these failing concrete foundations was largely mined from a single quarry in Willington (CT), within a stratified metamorphic unit mapped as Ordovician Brimfield Schist.

Pyrrhotite particles in coarse aggregates are unstable in oxidizing conditions. When exposed to water and oxygen, pyrrhotite oxidizes to form acidic-, iron-, and sulfate-rich by-products. One of these products is sulfuric acid which attacks the cement paste, weakening it, and generating sulfates as a by-product. These sulfates react with portlandite and hydrated aluminate phases in the paste, resulting in an expansion in the form of secondary minerals of greater volume. With more expansion and cracking occurring, more moisture is allowed in the concrete, exposing more pyrrhotite, and consequently increasing the rate of distress. At present no measure other than foundation replacement is known to reverse or eliminate pyrrhotite-Induced concrete deterioration.

According to the state Department of Housing, 42 towns and upwards of 35,000 homes in Connecticut could be potentially affected, primarily in the northeastern portion of the State. Single-family homes, home additions and detached garages, condominiums and other buildings are affected. Just north of the border, significant parts of south western Massachusetts could also be potentially affected although no precise numbers have been issued.

The problematic concrete allegedly originated from a single Stafford Springs (CT) concrete producer during the years 1983 – 2015. The company reportedly used reactive pyrrhotite-bearing rock aggregate from a quarry located in Willington (CT) for the fabrication of concrete for building foundations.

The main tell-tale signs of premature foundation deterioration caused by pyrrhotite-induced expansive reactions in concrete are: Map/web-like cracking patterns, horizontal cracking, spalling on surface of concrete, foundation walls bowing, rust-like discoloration on surface of concrete, white efflorescence (powder) in the vicinity of cracking surface. Cracks can rapidly evolve until the eventual loss of concrete strength.

Pyrrhotite Content

Although the undesirable nature of pyrrhotite for the manufacture of concrete is recognized and although contents as low as 0.3% pyrrhotite by mass of coarse aggregate have reportedly caused significant concrete distress (e.g., in Trois-Rivières, Canada), no precise value has been issued in any U.S. State or Federal laws, as to the maximum authorized pyrrhotite content in coarse aggregates for use in concrete. More research and case history data are needed to reveal with more accuracy the minimum level at which significant concrete deterioration will occur.

Sulfur Content

The European standard for coarse aggregate NF EN 12620 (article 6.3.2), in force since 2003, has placed a limit of 0.1% sulfur if pyrrhotite is identified in the coarse aggregate. In Canada, CSA A23.1 (R2014) states that aggregate susceptible to cause excessive expansion of the concrete due to the presence of sulfides (pyrite, pyrrhotite, marcasite) should not be used in concrete. In addition, this standard recommends not using aggregates containing pyrrhotite in new concrete if these aggregates bear sulfur content higher than 0.1%. The US Army Corps of Engineers recent recommendations state that aggregate for use in new concrete should be assumed pyrrhotite-bearing and should be accepted only if its sulfur content is below 0.1%.