Field Performance of Corrugated Pipe Manufactured with Recycled Polyethylene Content (2018)

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L-1 Proposed Standard Recommended Practice for Service Life Determination of Corrugated HDPE Pipes Manufactured with Recycled Materials The following pages contain a draft proposed AASHTO Standard Recommended Practice to determine the service life of corrugated HDPE pipes manufactured with recycled materials and to establish minimum UCLS guidelines to ensure the desired service life is met. A P P E N D I X L

L-2 Standard Recommended Practice for Service Life Determination of Corrugated HDPE Pipes Manufactured with Recycled Materials AASHTO Designation: M xxx-yy1 Technical Section: No., Name Release: Group n (Month yyyy)

L-3 Standard Recommended Practice for Service Life Determination of Corrugated HDPE Pipes Manufactured with Recycled Materials AASHTO Designation: M xxx-yy Technical Section: No., Name Release: Group n (Month yyyy) 1. SCOPE 1.1. This standard practice details the procedure for determining the service life of corrugated high density polyethylene (HDPE) pipes manufactured with recycled materials relative to Stage II brittle failures via the slow crack growth mechanism. 1.2. The service life determination in this standard practice is based on analysis of failure data from testing conducted in accordance to ASTM F3181, the Un-Notched Constant Ligament Stress (UCLS) test. 1.3. This standard practice can be used to establish minimum UCLS performance criteria to ensure a desired service life at given service conditions for corrugated HDPE pipes containing recycled materials. 1.4. This standard practice is applicable for pipes containing recycled materials and manufactured in accordance to AASHTO M 294. It is applicable both for pipes manufactured with post-consumer recycled (PCR) materials and post-industrial recycled (PIR) materials. It is not intended for pipes manufactured with virgin materials. 1.5. Units—The values stated in SI units are to be regarded as standard. Within the text, the U.S. Customary units are shown in parentheses, and may not be exact equivalents. 2. REFERENCED STANDARDS 2.1. AASHTO Standards: M 294 – Standard Specification for Corrugated Polyethylene Pipe, 300- to 1500-mm (12- to 60-in.) Diameter 2.2. ASTM Standards: F3181 - Standard Test Method for The Un-notched, Constant Ligament Stress Crack Test (UCLS) for HDPE Materials Containing Post-Consumer Recycled HDPE

L-4 D4703 - Standard Practice for Compression Molding Thermoplastic Materials into Test Specimens, Plaques, or Sheets 2.3. Other: Pluimer, Michael L. (2016). Evaluation of Corrugated HDPE Pipes Manufactured with Recycled Materials in Commuter Railroad Applications (Doctoral dissertation). Proquest Publishing, Villanova University. 3. TERMINOLOGY 3.1. Contaminant, n – inorganic particulate matter or other non-HDPE material that creates inclusions or stress risers in the crystalline structure of HDPE. 3.2. Crack initiation – the portion of the slow crack growth mechanism associated with the initial development of a craze zone and micro-cracks and around a contaminant, void or discontinuity (see Figure 1) 3.3. Crack propagation – the portion of the slow crack growth mechanism associated with successive yielding of HDPE material ahead of a crack tip (see Figure 1) 3.4. Popelar shift method (PSM) – A method of bi-directionally shifting brittle crack failure data from HDPE specimens tested at elevated temperatures and stresses to other service conditions for lifetime prediction. 3.5. Post-consumer recycled (PCR) HDPE materials - HDPE materials from products that have served a previous consumer purpose (for example, laundry detergent bottles, milk bottles and other consumer goods) 3.6. Post-industrial recycled (PIR) HDPE materials – HDPE materials diverted from the waste stream during a manufacturing process that have never reached the end user 3.7. Slow crack growth (SCG) – a failure mechanism for HDPE defined by brittle cracks that propagate through the material under conditions of tensile stresses lower than its short-term mechanical strength, also known as Stage II failures (see Figure 1); comprised of two phases: crack initiation and crack propagation Figure 1: Illustration of Stage II brittle failure, or slow crack growth (SCG) failure mechanism. The total time to failure is comprised of two phases: 1) The time for crack initiation, tCI and 2) The time for crack propagation, tCP (Pluimer 2016)

L-5 4. PROCEDURE FOR DETERMINING SERVICE LIFE OF CORRUGATED HDPE PIPES MANUFACTURED WITH RECYCLED MATERIALS 4.1. Prepare compression-molded UCLS plaques according to the procedures outlined in ASTM D4703 and ASTM F3181. The plaques may be prepared either from resin blends or from chips taken directly from the pipe wall. It is important that the materials are properly homogenized prior to compression molding into the plaque. Homogenization may be accomplished by a double pass through a twin-screw lab extruder or at least three passes through a single-screw lab extruder. 4.2. Prepare at least 15 UCLS test specimens from the plaques in accordance to the dimensions and procedures outlined in ASTM F3181. 4.3. Conduct the UCLS test in accordance to ASTM F3181 on five specimens at each of a minimum of three test conditions. Each specimen must be taken to failure. Record the individual and average failure times of the five specimens at each condition, as well as the coefficient of variation (the standard deviation of the failure times divided by the average failure time). The average must be calculated on a log basis. The minimum recommended test conditions are as follows: Condition I: 80 °C, 4.48 MPa (650 psi) stress Condition II: 80 °C, 3.10 MPa (450 psi) stress Condition III: 70 °C, 4.48 MPa (650 psi) stress 4.4. Use the PSM multiplication factors shown in Equations 1.1 and 1.2 to shift the elevated temperature (T2, °C) average failure times (determined on a log basis) from Step 4.3 to the projected failure times at the desired in-ground service temperature (T1, °C). 23 °C is a conservative assumption for T1, though lower temperatures may be specified if appropriate. Stress Shift Factor = e 0.0116 (T2-T1) (Eqn. 1.1) Time Shift Factor = e 0.109 (T2-T1) (Eqn. 1.2) 4.5. Plot the resulting three (or more, if additional conditions were evaluated) shifted average data points on a log-log scale, with log time on the X-axis and log stress on the Y-axis. Determine the best-fit curve for the data points, which should be linear on a log-log scale. 4.6. Calculate the 95% lower confidence limit (LCL) of each of the log-based average data points by using the Student’s t-distribution as shown in Equation 1.3. Use the largest COV from the three (or more) data sets obtained in Step 3 for determination of the LCL. (Eqn. 1.3) where LCL95% = Lower 95% Confidence Limit = Log-based average of 5 test specimens t(n-1) = Student’s t value at (n-1) degrees of freedom = 2.132 COV = Maximum coefficient of variation of 5 test specimens n = Number of test specimens at each condition = 5

L-6 4.7. Determine the best-fit curve for the three (or more) LCL data points. 4.8. Extrapolate the LCL curve to the desired factored service stress condition to determine the predicted service life relative to Stage II brittle cracking. The service life is calculated by solving the equation of the LCL curve at the desired stress condition. 4.9. An example of the procedure is illustrated in Appendix X1. 5. PROCEDURE FOR ESTABLISHING MINIMUM UCLS PERFORMANCE CRITERIA FOR A DESIRED SERVICE LIFE FOR CORRUGATED HDPE PIPES MANUFACTURED WITH RECYCLED MATERIALS 5.1. Follow the procedure described in 4.1 – 4.5 for at least 8 pipes manufactured with typical recycled material blends to determine the average slope of the brittle failure curve, m, when plotted on a log-log scale with log time on the X-axis and log stress on the Y-axis. In the absence of this data, a slope of -0.20 can be conservatively used based on the research reported in NCHRP Project 4-39. 5.2. Determine the COV for each 5-specimen data set from 5.1. Use the maximum COV from these data sets for the following calculations. In the absence of this data, a COV of 0.50 can be conservatively used based on the research reported in NCHRP Project 4-39. 5.3. Using Equations 1.4 and 1.5, calculate the minimum UCLS failure time at the desired test condition to ensure a desired service life (tSVC, hrs.) at the given service conditions [i.e. service stress ( SVC , psi ) and service temperature (T1, °C)]. It is suggested to use Test Condition I [80 °C and 4.48 MPa (650 psi) stress], as this is the most aggressive test condition and will generate the shortest failure times. (Eqn. 1.4) where tT = Minimum required average failure time at test condition, hrs. m = Slope of brittle failure curve SF = Popelar stress shift factor from Eqn. 1.1 SFt = Popelar time shift factor from Eqn. 1.2 = Stress at test condition, psi = Stress at service condition, psi tSVC = Required service life at service conditions, hrs. C T SVC = (Eqn. 1.5)

L-7 (Eqn. 1.6) where = Average failure time needed for 95% confidence, hrs. tT = Minimum required average failure time from Eqn. 1.4, hrs. t(n-1) = Student’s t value at (n-1) degrees of freedom = 2.132 COV = Maximum coefficient of variation from test data n = Number of test specimens at each condition = 5 5.5. An example calculation is shown in Appendix X2. APPENDIXES (Nonmandatory Information) X1. EXAMPLE CALCULATIONS FOR SERVICE LIFE DETERMINATION X1.1. An example process for determining the service life of a typical corrugated HDPE pipe manufactured with recycled materials is illustrated in the steps below. The data for this example analysis are shown in Table X1.1. X1.2. First, the UCLS test is conducted on pieces of pipe that have been compression-molded into a plaque and prepared in accordance to ASTM F3181. In this example, a total of 15 specimens were tested, 5 at each of the minimum conditions described in Section 4.3. X1.3. Record the failure time t of each specimen and calculate the arithmetic COV of each 5-specimen data set. X1.4. Take the logarithm (Log t) of each failure time and calculate the log-based average of each 5- specimen data set. X1.5. The LCL of the data is calculated by applying Equation 1.3 to the calculated log-based average failure times. Conservatively, the largest COV of the three (or more) test conditions is used in the calculations. An example calculation of the LCL for Condition I is shown in Equation X1.1. 56.1 hrs. (Eqn. X1.1) 5.4. To ensure 95% confidence that the minimum average failure time calculated from Equation 1.4 will result in the desired service life, the failure time must be statistically adjusted to account for the scatter in the data. The average failure time needed to ensure 95% confidence is calculated from Equation 1.6.

L-8 Stress Shift Factor = e 0.0116 (T2-T1) = e0.0116(80-23) = 1.937 (Eqn. X1.2) Time Shift Factor = e 0.109 (T2-T1) = e 0.109 (80-23) = 499.2 (Eqn. X1.3) Stress Shift Factor = e 0.0116 (T2-T1) = e0.0116 (70-23) = 1.725 (Eqn. X1.4) Time Shift Factor = e 0.109 (T2-T1) = e 0.109 (70-23) = 167.8 (Eqn. X1.5) X1.7. Shift the log-based average failure times and stresses and the calculated LCL times and stresses to the desired service temperature using the multiplication factors calculated in Step X1.6 for each condition. For example, the log-based average failure time from Condition I is shifted from the test conditions of 80 °C and 4.48 MPa (650 psi) stress to a service condition of (93.0)(499.2) = 46,447 hrs. at a stress of (4.48)(1.937) = 8.678 MPa (1259 psi). Similarly, the LCL from Condition I is shifted to (56.1)(499.2) = 28,012 hrs. at a stress of (4.48)(1.937) = 8.678 MPa (1259 psi). Similar calculations are performed for each test condition as shown in Table X1.1. X1.8. Plot the logarithm of the shifted data points for each condition and determine the best-fit curve. Extrapolate the best-fit curve to a minimum of 106 hours (114 years). Determine the equation of the best-fit curve. Figure X1.1 shows a plotted curve for the data in this example. X1.9. Repeat X1.8 for the shifted LCL data points to determine the equation of the LCL curve (see Figure X1.1 for the data in this example) X1.10. To calculate the service life for the material at a given stress, solve the LCL curve shown in Figure X1.1 for “x”. For example, to calculate the service life at a stress of 500 psi (2.699 on a log basis), the service life is calculated as shown in Equations X1.6 and X1.7: (Eqn. X1.6) (Eqn. X1.7) X1.6. Determine the multiplication factors for each test condition using Equations 1.1 and 1.2. For example, to shift the data from Conditions I and II to a service temperature of 23 °C, the multiplication factors shown in Equations X1.2 and X1.3 are used; to shift the data from Condition III to a service temperature of 23 °C, the multiplication factors shown in Equations X1.4 and X1.5 are used.

L-9 1 Average of the five log failure times (see X1.4) 2 Arithmetic COV of the five failure times 3 Average log-based failure time (see X1.4) 4 Average log-based failure time shifted to 23 °C condition (see X1.6 and X1.7) 5 Logarithm of the shifted failure time 6 Lower 95% confidence limit of the average log-based failure times, based on the maximum COV of the 3 conditions (see X1.5) 7 Lower 95% confidence limit shifted to 23 °C condition (see X1.6 and X1.7) 8 Logarithm of the shifted 95% LCL 9 Stress shifted to 23 °C condition (see X1.6 and X1.7) 10 Logarithm of the shifted stress Figure X1.1: An illustration of the average and LCL curves for a typical pipe containing 49% PCR materials. In this example, the predicted service life relative to Stage II brittle cracking is 234 years. Table X1.1: Summary of test data and calculations for example problem for pipe manufactured with 49% PCR materials Specimen Condition I: 80 °C/ 4.48 MPa (650 psi) Condition II: 80 °C/ 3.10 MPa (450 psi) Condition III: 70 °C/ 4.48 MPa (650 psi) t (hr) Log(t) t (hr) Log(t) t (hr) Log(t) 1 130.0 2.114 773.9 2.889 932.9 2.970 2 75.7 1.879 250.6 2.399 661.2 2.820 3 125.9 2.100 372.4 2.571 539.1 2.732 4 98.6 1.994 702.2 2.846 378.4 2.578 5 57.1 1.757 705.7 2.849 351.0 2.545 Calculations Condition I Condition II Condition III 1.969 2.711 2.729 0.323 0.416 0.415 93.0 hrs. 513.7 hrs. 535.8 46,447 hrs.X 256,462 hrs. 89,931 hrs. 4.667 hrs. 5.409 hrs. 4.954 hrs. 56.1 hrs. 309.8 hrs. 323.1 hrs. 28,012 hrs. 154,671 hrs. 54,237 hrs. 4.447 hrs. 5.189 hrs. 4.734 hrs. 1259 psi 871.7 psi 1121 psi 3.100 psi 2.940 psi 3.050 psi COV2 3 23 4 LCL6 LCL237 σ239 Log(σ23)10 Log(LCL23)8 Log(X23)5 Log(t)1 X Avg: y = -0.2175x + 4.1196 R² = 0.9936 LCL: y = -0.2175x + 4.0719 R² = 0.9936 2.6 2.7 2.8 2.9 3.0 3.1 3.2 Lo g St re ss (p si ) Log Time (hrs) Mastercurve at 23 deg. C 2.05E6 hrs. = 234 yrs. 500 psi stress 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

L-10 X2.4. Using Equations 1.1 and 1.2, the stress and time shift factors are calculated as shown in Equations X2.1 and X2.2. Stress Shift Factor = SF = e 0.0116 (80-23) = 1.937 (Eqn. X2.1) Time Shift Factor = SFt = e 0.109 (80-23) = 499.2 (Eqn. X2.2) X2.5. Using Equation 1.5, calculate C as illustrated in Equation X2.3. C (Eqn. X2.3) = 3.937 X2.6. Using Equation 1.4, calculate the minimum average failure time, tT,650,80, for Condition I. This is shown in Equation X2.4. (Eqn. X2.4) X2.7. To ensure 95% confidence that the average failure time meets this requirement, use Equation 1.6 to statistically adjust this number to determine the test requirement for the minimum average failure time. This is demonstrated in Equation X2.5. (Eqn. X2.5) X2.8. Rounding up for conservatism, the minimum average UCLS failure time for five specimens at Condition I [80 °C and 4.48 MPa (650 psi) stress] should be 34 hours to ensure 100-year service life in conditions that result in a factored tensile wall stress of 500 psi at a temperature of 23 °C. Furthermore, no single specimen should fail in less than 18 hours. X2. EXAMPLE CALCULATIONS FOR DETERMINING MINIMUM UCLS CRITERIA TO ENSURE DESIRED SERVICE LIFE AT GIVEN SERVICE CONDITIONS X2.1. An example process for determining the minimum UCLS failure time at Condition I [80 °C and 4.48 MPa (650 psi) stress] for a given set of service conditions is illustrated below. X2.2. For this example, the service conditions required by the Florida DOT for 100-year applications for corrugated HDPE pipes are used. Namely, the Florida DOT requires corrugated HDPE pipes to last 100 years (876,000 hrs.) at a factored tensile wall stress of 3.4 MPa (500 psi) and an underground service temperature of 23 °C. X2.3. In the absence of other data, a brittle slope of -0.20 and a COV of 0.50 are conservatively assumed for the calculations.

Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FAST Fixing America’s Surface Transportation Act (2015) FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) NASA National Aeronautics and Space Administration NASAO National Association of State Aviation Officials NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program NHTSA National Highway Traffic Safety Administration NTSB National Transportation Safety Board PHMSA Pipeline and Hazardous Materials Safety Administration RITA Research and Innovative Technology Administration SAE Society of Automotive Engineers SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) TCRP Transit Cooperative Research Program TDC Transit Development Corporation TEA-21 Transportation Equity Act for the 21st Century (1998) TRB Transportation Research Board TSA Transportation Security Administration U.S.DOT United States Department of Transportation

TRA N SPO RTATIO N RESEA RCH BO A RD 500 Fifth Street, N W W ashington, D C 20001 A D D RESS SERV ICE REQ U ESTED N O N -PR O FIT O R G . U .S. PO STA G E PA ID C O LU M B IA , M D PER M IT N O . 88 Field Perform ance of Corrugated Pipe M anufactured w ith Recycled Polyethylene Content N CH RP Research Report 870 TRB ISBN 978-0-309-44677-8 9 7 8 0 3 0 9 4 4 6 7 7 8 9 0 0 0 0