FHWA OFFICE OF BRIDGE TECHNOLOGY

PT Grout With Elevated Chlorides

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2014 TRB Annual Meeting

Long-Term Bridge Performance Program Workshop
January 16, 2014

Reggie Holt, P.E.
Federal Highway Administration

Background

• PT grout with elevated chlorides was initially discovered in a PT straddle cap in TX (2010).
  
  
• PT grout used in TX bridge was a pre-bagged thixotropic product called SikaGrout 300PT.
  
  
• PT grout manufacturer, Sika, determined that its 300PT SikaGrout product from its Marion OH plant was sometimes produced with levels of chloride well above the specified limit. (0.08% by wt. of cement)
  
  
• The cement used in the 300PT product has been identified as the source of the chlorides.

Background

• SIkaGrout 300PT was produced at the Marion OH plant from 2001 to 2010.
  
  
• Production of 300PT was ceased at the Marion OH plant in April 2010.
  
  
• To date approximately 88% of the Marion OH produced 300PT grout has been located.
  
  
• Approximately 24M lbs. was produced with approx. 16M lbs. used in bridge applications (approx. 120 bridge projects).

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Background

Production Year	Number of Samples Tested	Number of Lots Represented	Total Lots Produced by Sika	Acid Soluble %Cl by Weight of Cement Range	Average Acid Soluble %Cl by Weight of Cement	Weighted Average Acid Soluble %Cl by Weight of Cement
2001			5
2002	9	2	20	0.038-0.088	0.063	0.054
2003	20	5	22	0.032-0.116	0.076	0.073
2004	49	19	37	0.011-0.116	0.053	0.043
2005	63	24	44	0.010-0.224	0.051	0.048
2006	116	26	52	0.024-0.203	0.106	0.105
2007	25	6	23	0.034-0.309	0.130	0.136
2008	28	14	24	0.073-0.483	0.201	0.158
2009	25	5	18	0.018-0.360**	0.130	0.127
2009	104*	18	18	0.002-0.564	0.150	0.138
2010	14*	1	1	0.088-0.171	0.107	0.107
Total	453	120	264	0.002-0.564	0.103	0.093

Chloride Testing Data

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Background



Maximum Chloride Concentrations

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FHWA Technical Advisory (TA)



https://www.fhwa.dot.gov/bridge/t514033.pdf

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FHWA Technical Advisory (TA)

• Guidance by FHWA to assess and manage long-term performance of PT bridges having tendons installed with grout containing elevated levels of chlorides.
  
  
• Steps used in TA for assessment:
  • Determine PT Grout Chloride Level
  • Determine PT System Robustness (protection level)
  • Determine Corrosion Risk Level
  • Assess Bridge System Redundancy & PT Element Ductility
  • Determine Management Follow-up Actions

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Step 1 - Determine PT Grout Chloride Level

• Check Grout Records (if available)
  
  
• Determine Chloride Level by:
  • Use Sika Production Catalog
  • Sample In-place Grout
  • Assume Highest Chloride Level for that Production Year



 

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Step 2 - Determine PT Tendon Robustness

• Review Bridge Drawings to Identify PT Details and Components
  
  
• Compare Details & Components to Protection Level Requirements in PTI / ASBI Guide Specification for Grouted Post-Tensioning (June 2012)
  • PL1A, PL1B, PL2 & PL3



 

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Step 3 - Determine Corrosion Risk Level

• Research was needed to provide basis on which tolerable chloride concentrations could be identified.

Sika Research	FHWA Research

 

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Step 3 - Determine Corrosion Risk Level

• Research findings
  • Both research teams agreed that sustained corrosion was definitively observed at chloride concentrations above 0.75%.
  • One researcher observed minor and possibly sustained corrosion at 0.40% and suggested that additional research should be directed at understanding the long term importance of this observation.

 

Protection Level	Chloride Concentration (% Cl- per wt. of cement)
	≤ 0.08%	0.08%< Cl- ≤0.30%	0.30%< Cl- ≤0.50%	0.50%< Cl- ≤0.65%	> 0.65%
PL-1A	No Risk	RL 1	RL 2	RL 3	RL 4
PL-1B		RL 1	RL 2	RL 3	RL 4
PL-2 & PL-3		RL 1	RL 2	RL 2	RL 4

Corrosion Risk Level

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Step 4 - Assess Bridge System Redundancy and Element Ductility

Structure Class	Redundancy  & Ductility Indicators	Expected Performance
S1	System factor (Øs) ≥ 1.10 & Pass ductility check	A highly redundant bridge that will develop easily detectable cracking before debilitating strength loss.
S2	1.10 > System factor (Øs) ≥ 1.0 & Pass ductility check	A moderately redundant bridge that will develop easily detectable cracking before debilitating strength loss
S3	System factor (Øs) < 1.0 or Fail ductility check	A bridge with limited ductility and/or redundancy.

Structure Classification

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Step 5 - Determine Management Follow-up Actions

• Using results from previous 4 steps, management and follow-up actions are determined.
  
  
• The follow-up actions range from:
  • No additional measures needed
  • Biennial in-depth inspection needed *
  • Annual in-depth inspection *
  • Plan repairs / replacement

*Undesirable inspection findings should
activate special inspection or monitoring.

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Step 5 – Determine Management Follow-up Actions

Structure Classification Corrosion Risk Level S1 S2 S3 RL 1 FA I FA I FA II RL 2 FA I FA II FA III RL 3 FA II FA III FA III RL 4 FA IV FA IV FA IV Management Follow-up Actions

Management Follow-up Actions (FA) FA I – no additional measures needed FA II – biennial in-depth inspection needed * FA III – annual in-depth inspection needed * FA IV - plan repairs / replacement * Undesirable inspection findings should activate special inspection or monitoring

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Next Steps

• Follow-up with DOT’s.
  
  
• Possible additional in-place sampling to provide data for production years with limited data.

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Thank You

Reggie Holt, P.E.
Federal Highway Administration
Reggie.holt@dot.gov

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