This document summarizes non-destructive testing methods used to evaluate prestressed concrete cylinder pipe (PCCP) for a water treatment plant in Ohio. Soil samples were taken and tested for resistivity, stray currents, chloride, sulfate, and pH levels. Visual inspections of exposed pipe joints showed the PCCP to be in good condition with loose grout. The soil was found to not be corrosive and no failures were observed. Access hatches showed surface corrosion and were recommended for further inspection and potential rehab. Future testing of metal connections and joint grout was also recommended.

1. Non-Destructive Testing & Evaluation of
Prestressed Concrete Cylinder Pipe (PCCP):
A Proactive & Budget Conscious Approach
AWWA Ohio Section
2012 Conference

2. Prestressed Concrete Cylinder Pipe (PCCP)
 Steel Cylinder Pipe, Concrete Core, Prestressing wire, Exterior
Cementitious Mortar and Grout
 Alkaline pH (12.5-13.5) cement = passive oxide film
 AWWA C301 – 1949 (Manufacturing Standard)
– 1942 Concrete Lined
– 1952 Concrete Embedded
 AWWA C304 – 1992 (Design Standard)
 1970s – Substandard wire manufacturing
 90% of largest water utilities have PCCP

3. Concrete Lined (AWWA C301)

4. Concrete Embedded (AWWA C301)

5. Diaper and Joint Grout Installation

8. City of Elyria, Ohio
 22 MGD WTP
– Located on shore of Lake Erie
– Lake Erie surface water
 Customers
– Elyria
– Amherst
– North Ridgeville
– Northern Ohio Rural Water
 C301 Lined PCCP (Lined)
– 4 miles of 48”
– 3 miles of 36”

9. Why Be Proactive?
 Installed 1958 (54 years old)
– no previous inspections
 “Stories” of failures and leaks
 Primary Transmission Mains
 Access Issues
– park, roadways, residential property, high school
 PCCP can fail with little or no warning
 Sense of Stewardship! Customers – they depend on us!
 Goal – General Condition Assessment

10. Evaluation Methods vs. Relative Cost
 Stray Current Study
 Visual (Exterior)
 Soils Analysis
 Petrographic Testing
 Sonic/Ultrasonic Thickness Testing
 Ground Penetrating Radar (GPR)
 Acoustic Monitoring
 Leak Detection
 Infrared
 Sounding
 Structural Analysis (Finite Element Modeling)
 Electromagnetic Testing
 Real-Time Continuous Monitoring

11. Typical Failure & Related Factors
 Exterior Failures = Exterior Factors = Primary Concern
 Cementitious mortar surface compromised
– Breaks, cracks, spalling, pitting, delamination
– Prestressing wires and joints at risk
 Exterior Environmental Factors
– Electrochemical corrosion
– Stray Currents
– Chemical/Acid
– Microbiological
 Exterior Physical Factors
– Construction damage, bedding, materials, design, exposed surfaces, site conditions

12. Evaluation Methodology
 Team Collaboration! Meetings, Discussions, Interviews
 Verification of Historical Data and “Stories”
– Only one documented failure (hydrant lateral)
– No actual documentation of leaks or breaks
 Assumed failure modes and contributing factors
 Impacts to service
 Destructive vs. Non-Destructive
 Cost Evaluation

13. Evaluation Methods Chosen
 Soils Analysis – Step 1
– Resistivity
– Stray Currents
– Ions
– pH (acidity)
 Excavation – Step 2
– Visual inspection at joints
– Weigh Soils Analysis results
– Space out along route
– Access considerations

14. Soil Resistivity (ohm-cm) – Four Pin Method
 Inverse of conductivity
 Lower resistivity = easier current movement through soil
 5,000-2,000 = Corrosive (metals)
 Less than 2,000 = Highly corrosive (metals)
 Less than 1,500 = Corrosive (cementitious materials)
 Test Results = 5,400-4,500

15. Stray Currents
 DC flowing underground
– Cathodic protection, grounding systems, electric railway, arc-welding
 AC flowing overhead and underground
– Electrical transmission lines (electromagnetically induced, flaw in line)
 Accumulates/travels on pipe
 Discharges from Anode to Cathode
– Prefers long, electrically continuous runs, path of least resistance
– Can cause corrosion damage where it discharges from pipe
 Structure to Soil Potential Test
– Prefer to do over time and on electrically continuous pipe
 Visual Inspection and Utilities Research

16. Chloride Ions (ppm)
 Common source = Deicing activities
 Disrupt passive protective film
 Not consumed – initiate and sustain corrosion
 Greater than 400 ppm = Corrosive (cementitious materials)
 Test Results = 2 – 180 ppm

17. Sulfate/Sulfide Ions (ppm)
 Sulfates (calcium, sodium, magnesium – alkali soils)
– Chemical attack
– Greater than 2,000 ppm = Corrosive (cementitious materials)
– Test Results = 96 – 330 ppm
 Sulfate Reducing Bacteria (SRB) may be present
– Microbiological attack
– Moisture, clay, muck, organics (anaerobic conditions)
 Sulfides
– SRB reduces sulfates to sulfides (H2S, sulfuric acid)
– Test Results = None detected

18. pH
 Acid attacks uncommon in soils
– Typically not natural, needs to be replenished
 Less than 5.0 = strong acid
 Less than 4.0 = extremely acidic
 Test Results = 5.6 – 9.4
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
pH 7.0 = Neutral
Extremely Acidic
pH <4
Acid
pH 5 to 7
Basic (Alkaline)
pH >7

19. Excavation & Visual Inspection
 48” PCCP – 4 locations
 36” PCCP – 2 locations
 Local Contractor
– Prequalified by City
– Experience on City utilities
 Project Team on-site
 Target pipe joints

29. Visual Inspection Results
 Pipe = good condition
 Joints = good condition
– Grout diaper and steel bands still evident
– Joint recesses still tightly packed
– Joint grout was loose and fell away
– Observations not uncommon for age and construction methods
 Access Hatches
– Surface corrosion, appear structurally sound

30. Findings & Recommendations
 Soils tested were found not to be corrosive to PCCP.
 No failures or precursor conditions to failure were observed
during testing and visual inspection.
 PCCP in GOOD condition.
 Access Hatches
– Visual inspection, clean, ultrasonic thickness test, protective coating,
rehab or replace as necessary.
 Future Testing/Inspection Considerations
– Metal pipe connections
– Joint Grout – petrographic testing, replace grout

31. Questions?
Tim Antos, PE
Burgess & Niple, Inc.
timothy.antos@burgessniple.com
(440) 354-9700