How To Test For Hydrogen Embrittlement

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Oswald Knight
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1 AC R1 #9 Hydrogen Embrittlement of Concrete Screw Anchors: Method A vs Method B Comparison H 2 H 2 O H Anthony J. Lamanna, Ph.D., P.E. Assistant Professor Department of Applied Engineering and Technology College of Business and Technology Eastern Kentucky University October 2015

2 Contributing Factors Materials Susceptible Environment Stress

3 Cross Section

4 Hardness Profile Pre-Qualified Limit

5 Test Method A Overview 240 or 100 hours = Pass N sustained = min 0.7 N u,mean 0.5 N st,mean Ca(OH) 2 Solution ph = 12.6 Electrochemical Potential

6 Test Method A Overview

7 Test Method B Overview (P max environmental 0.70 P confinedair ) = Pass Salt Water Environment Corrosion Potential Controlled Tip & Head Removed

8 Results Database 23 Distinct Products 5 diameters 11 embedment lengths 115 individual Method A Alternate Tests 112 A Alternate tests had brittle steel failure 42 individual tests for Method B 42 B tests had brittle steel failure

9 Results Database High Method B Equivalent Threshold Tensile Load Ultimate Tensile Load Ave Low 1

10 Results Database High Method B Equivalent Threshold Tensile Load Method A Residual Failure Load Ave Low 1

11 Results Database High Method B Equivalent Threshold Tensile Load Method A Residual Failure Load 1 Ave Low

12 Conclusions 1. Method A provides lower strength values than Method B. 2. Method A addresses hydrogen embrittlement susceptibility of an embedded anchor, not just the anchor itself.

13 Conclusions 3. Method A provides a residual load capacity that is used to determine the anchor category. 4. Method B is provides addresses the hydrogen embrittlement susceptibility of the shank of the anchor only.

14 Conclusions 5. The large range of capacities among anchors in a certain diameter or length underscores the importance of qualification testing.

15 Recommendations Based on review of Method A and Method B test results, Method A is more conservative and yields useable strength numbers while Method B does not. Therefore, it is recommended that Method B removed from AC 193.

16 Special Thanks Manufacturers who contributed data! (3 of them) Questions?

17 AC R1 #9 Relative stress values of the various hydrogen embrittlement test methods to the Objective of AC193 LRA/RSL Testing Laboratory POB 10239, Newport Beach, CA Phone:

18 Outline Objective of AC193 Method A Method B Closing Remarks Outline Objective of AC193 Method A Approach Result Conclusion Method B Approach Result Conclusion Closing Remarks Method A Method B LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

19 Outline Objective of AC193 Method A Method B Closing Remarks Objective of AC193 Verify sufficient insensitivity to stress-induced hydrogen embrittlement cracking under conditions as may occur in service. AC193 Section 8.7.1, Pg. A17, May 2013 LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

20 Outline Objective of AC193 Method A Method B Closing Remarks Method A Approach SLT at 70% of Confined Pullout Load UTS Failure Load = f(length and Diameter) Embedded in concrete and basic CaOH2 solution at -1.2 Vsce LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

21 Outline Objective of AC193 Method A Method B Closing Remarks Method A (Cont.) Result Pass / Fail How much wait time is sufficient? hrs is long enough depending on the use of a wedge under head Failure is defined as crack initiation in the core Recent developments have reduced the core hardness to << 39 HRC LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

22 Outline Objective of AC193 Method A Method B Closing Remarks Method A (Cont.) Conclusion Results subject to variability of the Confined Pullout Load Does not take into account bending Way too conservative No margin of safety in bending Per ASTM E1681 (SLT SCC), a hold time of 10,000 hrs is required to determine the onset of crack growth for HRC 39 LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

23 Outline Objective of AC193 Method A Method B Closing Remarks Method A (Cont.) Conclusion (Cont.) METHOD A does not wait long enough at a sustained load to determine the onset of crack growth. METHOD A does not meet the HE objectives of STD AC193 METHOD A will not Prevent HE FAILURES in Anchor Screws LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

24 Outline Objective of AC193 Method A Method B Closing Remarks Method B Approach RSL(B) to 2 UTS 3x 70% Confined Pullout Load Failure Load is Only a Function of Diameter Immersed in slightly acidic 3.5% NaCl solution at -1.2 Vsce Hydrogen embrittlement is only a function of imposed potential, NOT chemical composition of the solution (Sheldon Dean) LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

25 Outline Objective of AC193 Method A Method B Closing Remarks Method B (Cont.) Result Provides a quantitative measurement of the HE cracking threshold stress Applies to all lengths LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

26 Outline Objective of AC193 Method A Method B Closing Remarks Method B (Cont.) Conclusion Results are directly applicable to all lengths If greater than Confined Pullout Load, definitely will withstand 70% Confined Pullout Load Bending taken into account to fracture Quantitatively specified Margin of Safety F519, F1624, F2660 Acceptance Criterion Hsr = 1.2 = 2x Method A Acceptance Criterion LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

27 Outline Objective of AC193 Method A Method B Closing Remarks Method B (Cont.) Conclusion (Cont.) METHOD B does meet the HE objectives of STD AC193 METHOD B will prevent HE FAILURES of Anchor Screws LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

28 Outline Objective of AC193 Method A Method B Closing Remarks RSL Testing RSL testing was utilized to determine resistance to hydrogen embrittlement stress cracking for 1 to 4 diameter threaded rod used on east span of San Francisco-Oakland Bay Bridge Established margin of safety for various threaded rods embedded into concrete Caltrans report can be found at LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

29 Outline Objective of AC193 Method A Method B Closing Remarks Closing Remarks METHOD A does not meet the HE objectives of STD AC193 because it will not Prevent HE failures of the Anchor Screw it is based on anchor pullout or concrete cone failure. METHOD B does meet the HE objectives of the STD AC193 because it will prevent HE failures of Anchor Screws it is based on the resistance of the screw to hydrogen embrittlement cracking. LRA/RSL Testing Laboratory [email protected] POB 10239, Newport Beach, CA Phone:

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