Characterization of
Characterization of
H2S-Induced Concrete Corrosion Using Established and New Methods
Scott Schaefer, PE Co-authors: M. Schaefer, M. Massey, V. Schaefer, and S. Fendorf WEFTEC 2016 Presented by: Advanced Engineering and Environmental Services, Inc. (AE2S)
Study Overview
Samples from six municipalities, four states Elemental analyses and traditional methods Observed corrosion penetration and corrosion product formation Best samples: 3.5-km interceptor with abrupt H2S (> 1,000 ppm) from a new SIU FRP insert rehabilitation
H2S CORROSION FUNDAMENTALS SAMPLING & TESTING METHODS STUDY RESULTS CONCLUSIONS
H2S Corrosion
FUNDAMENTALS
FUNDAMENTALS – SOURCES OF H2S H2S CORROSION FUNDAMENTALS
Regional Water Supplies High in Sulfate Significant Industrial User (SIU) Discharges • • •
Sulfate Sulfides Low pH and/or high strength organics/TKN
Water Conservation / I&I reduction •
Less water = longer retention time = anaerobic
Regionalization •
Longer collection systems = longer retention time = anaerobic
The Sewer Sulfur Cycle H2S CORROSION FUNDAMENTALS
Reference: WERF, 2007
FUNDAMENTALS RECAP H2S CORROSION FUNDAMENTALS
Corrosion Due to Acid Attack • •
Sulfuric acid formation Attacks – Concrete (simplified attack) H2SO4 + CaCO3 (concrete) = H2CO3 + CaSO4 (gypsum) – Metals
Sampling & Testing
METHODS
INDUSTRIAL IMPACTS TRADITIONAL SAMPLING/TESTING SAMPLING & TESTING METHODS
Problem •
Industrial Discharge with high H2S (100s to >1,000 ppm measured)
•
Rapid corrosion of 64 downgradient concrete manholes by acid attack
•
¼’ to ½’ concrete lost in ~2 months
•
Phenolphthalein staining confirmation
Interior Concrete Being Scraped
TRADITIONAL SAMPLING/TESTING SAMPLING & TESTING METHODS
75 mm (3”) diameter core samples from manholes Rebound hammer field tests: Manhole structural integrity Cores split and phenolphthalein stain tested: acid penetration H2S Measurement Multi-gas safety meters (spot check) OdaLog units (continuous)
Five additional communities sampled
TOOLS
SAMPLING & TESTING METHODS
SAMPLING & TESTING METHODS
4-GAS METER
ODALOGGER
REBOUND HAMMER
TOOLS
SAMPLING & TESTING METHODS
SAMPLING & TESTING METHODS
CORE DRILL
CORE PLUG
FISHING NET
ELEMENTAL COMP TESTING SAMPLING & TESTING METHODS
Total elemental composition by x-ray fluorescence (XRF), hand-held Bruker S1 Titan-LE unit interior face exterior face 3 cm from interior face
Comparison samples ground to fine powder and analyzed by bulk XRF (Spectro XEPOS).
ELEMENTAL COMP XRD & XAS TESTING SAMPLING & TESTING METHODS
Bulk sulfur x-ray absorption spectroscopy (XAS) performed at Beamline 4-3 at the Stanford Synchrotron Radiation Lightsource (SSRL) . X-ray microprobe imaging and spectroscopy at Beamlines 14-3 and 10-2.
Study
RESULTS
INDUSTRIAL IMPACTS STUDY RESULTS
Phenolphthalein staining
INDUSTRIAL IMPACTS STUDY RESULTS
Sewer Sample Locations, H2S Conc., & Elemental Ca & S Abundance Measurements
Sample Location Upstream Mixing Manhole Downstream 1 Downstream 1 Downstream 1 Downstream 2 Downstream 3 Downstream 4 Downstream 5
Sampling H2S Average Depth (ft) (ppm) 6 7 3.5 6.5 10.5 6.5 3.5 8 3.5
H2S Maximum (ppm)
Not Determined
Not Determined
183 711 711 711 106
835 >1,000 >1,000 >1,000 130
Not Determined
Not Determined
Not Determined
Not Determined
61
163
Calcium Sulfur (%) (%) 21.27 7.78 3.62 9.96 5.52 10.31 11.57 6.30 11.90
0.22 10.30 5.65 14.06 8.23 3.49 14.65 26.37 15.74
Ca:S 96.68 0.72 0.64 0.71 0.62 5.33 0.79 0.36 0.74
INDUSTRIAL IMPACTS STUDY RESULTS
Sulfur Bulk Abundance by XRF Higher on interior surface vs exterior surface for all samples except upstream control MH Upstream Control Mixing Manhole Closest Downstream Manhole Further Downstream Manholes
25 20 15 10 5
Distance from Interior of Manhole [cm]
20
15
10
5
0
0
S u lfu r A b u n d a n c e [% ]
•
MUNICIPAL CONCRETE SAMPLES STUDY RESULTS
Sulfur Bulk Abundance & Ca:S Ratio Measurements (Proxy for extent of sulfide/sulfate corrosion of concrete) Various Lower H2S Concentrations and Time Exposures
Sample ID MCS1 MCS2 MCS3 MCS4 MCS5 MCS6
Calcium (%) 3.53 13.90 0.69 14.67 3.25 7.99
Sulfur (%) 2.75 25.81 0.83 14.19 9.67 7.40
Ca:S 1.03 0.43 0.67 0.83 0.27 0.86
CALCIUM:SULFUR RATIO INTERPRETATION STUDY RESULTS
Ca:S Ratio
Interpretation
>1
High Ca, less corrosion
=1
Stoichiometric gypsum ratio (main corrosion product, Mori et al. 1992)
H2S-Induced Concrete Corrosion Using Established and New Methods
Scott Schaefer, PE Co-authors: M. Schaefer, M. Massey, V. Schaefer, and S. Fendorf WEFTEC 2016 Presented by: Advanced Engineering and Environmental Services, Inc. (AE2S)
Study Overview
Samples from six municipalities, four states Elemental analyses and traditional methods Observed corrosion penetration and corrosion product formation Best samples: 3.5-km interceptor with abrupt H2S (> 1,000 ppm) from a new SIU FRP insert rehabilitation
H2S CORROSION FUNDAMENTALS SAMPLING & TESTING METHODS STUDY RESULTS CONCLUSIONS
H2S Corrosion
FUNDAMENTALS
FUNDAMENTALS – SOURCES OF H2S H2S CORROSION FUNDAMENTALS
Regional Water Supplies High in Sulfate Significant Industrial User (SIU) Discharges • • •
Sulfate Sulfides Low pH and/or high strength organics/TKN
Water Conservation / I&I reduction •
Less water = longer retention time = anaerobic
Regionalization •
Longer collection systems = longer retention time = anaerobic
The Sewer Sulfur Cycle H2S CORROSION FUNDAMENTALS
Reference: WERF, 2007
FUNDAMENTALS RECAP H2S CORROSION FUNDAMENTALS
Corrosion Due to Acid Attack • •
Sulfuric acid formation Attacks – Concrete (simplified attack) H2SO4 + CaCO3 (concrete) = H2CO3 + CaSO4 (gypsum) – Metals
Sampling & Testing
METHODS
INDUSTRIAL IMPACTS TRADITIONAL SAMPLING/TESTING SAMPLING & TESTING METHODS
Problem •
Industrial Discharge with high H2S (100s to >1,000 ppm measured)
•
Rapid corrosion of 64 downgradient concrete manholes by acid attack
•
¼’ to ½’ concrete lost in ~2 months
•
Phenolphthalein staining confirmation
Interior Concrete Being Scraped
TRADITIONAL SAMPLING/TESTING SAMPLING & TESTING METHODS
75 mm (3”) diameter core samples from manholes Rebound hammer field tests: Manhole structural integrity Cores split and phenolphthalein stain tested: acid penetration H2S Measurement Multi-gas safety meters (spot check) OdaLog units (continuous)
Five additional communities sampled
TOOLS
SAMPLING & TESTING METHODS
SAMPLING & TESTING METHODS
4-GAS METER
ODALOGGER
REBOUND HAMMER
TOOLS
SAMPLING & TESTING METHODS
SAMPLING & TESTING METHODS
CORE DRILL
CORE PLUG
FISHING NET
ELEMENTAL COMP TESTING SAMPLING & TESTING METHODS
Total elemental composition by x-ray fluorescence (XRF), hand-held Bruker S1 Titan-LE unit interior face exterior face 3 cm from interior face
Comparison samples ground to fine powder and analyzed by bulk XRF (Spectro XEPOS).
ELEMENTAL COMP XRD & XAS TESTING SAMPLING & TESTING METHODS
Bulk sulfur x-ray absorption spectroscopy (XAS) performed at Beamline 4-3 at the Stanford Synchrotron Radiation Lightsource (SSRL) . X-ray microprobe imaging and spectroscopy at Beamlines 14-3 and 10-2.
Study
RESULTS
INDUSTRIAL IMPACTS STUDY RESULTS
Phenolphthalein staining
INDUSTRIAL IMPACTS STUDY RESULTS
Sewer Sample Locations, H2S Conc., & Elemental Ca & S Abundance Measurements
Sample Location Upstream Mixing Manhole Downstream 1 Downstream 1 Downstream 1 Downstream 2 Downstream 3 Downstream 4 Downstream 5
Sampling H2S Average Depth (ft) (ppm) 6 7 3.5 6.5 10.5 6.5 3.5 8 3.5
H2S Maximum (ppm)
Not Determined
Not Determined
183 711 711 711 106
835 >1,000 >1,000 >1,000 130
Not Determined
Not Determined
Not Determined
Not Determined
61
163
Calcium Sulfur (%) (%) 21.27 7.78 3.62 9.96 5.52 10.31 11.57 6.30 11.90
0.22 10.30 5.65 14.06 8.23 3.49 14.65 26.37 15.74
Ca:S 96.68 0.72 0.64 0.71 0.62 5.33 0.79 0.36 0.74
INDUSTRIAL IMPACTS STUDY RESULTS
Sulfur Bulk Abundance by XRF Higher on interior surface vs exterior surface for all samples except upstream control MH Upstream Control Mixing Manhole Closest Downstream Manhole Further Downstream Manholes
25 20 15 10 5
Distance from Interior of Manhole [cm]
20
15
10
5
0
0
S u lfu r A b u n d a n c e [% ]
•
MUNICIPAL CONCRETE SAMPLES STUDY RESULTS
Sulfur Bulk Abundance & Ca:S Ratio Measurements (Proxy for extent of sulfide/sulfate corrosion of concrete) Various Lower H2S Concentrations and Time Exposures
Sample ID MCS1 MCS2 MCS3 MCS4 MCS5 MCS6
Calcium (%) 3.53 13.90 0.69 14.67 3.25 7.99
Sulfur (%) 2.75 25.81 0.83 14.19 9.67 7.40
Ca:S 1.03 0.43 0.67 0.83 0.27 0.86
CALCIUM:SULFUR RATIO INTERPRETATION STUDY RESULTS
Ca:S Ratio
Interpretation
>1
High Ca, less corrosion
=1
Stoichiometric gypsum ratio (main corrosion product, Mori et al. 1992)
