|FHWA > Bridge > Elevated Chloride Levels in SikaGrout® 300 PT Cementitious Grout|
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Our memorandum of November 23, 2011, initially described potentially elevated chloride levels in SikaGrout 300 PT cementious grout and provided relevant background and descriptive information. Since distributing that memorandum, several efforts have been initiated to support addressing this issue. The purpose of this memorandum is to (1) update you on the status of our evaluation of the varying levels of chloride found in SikaGrout 300 PT Grout produced at the Marion, Ohio, plant between November 2002 and March 2010, (2) provide interim guidance on how to increase assurance that this issue will not occur again in the near future, and (3) to ask for assistance in developing information on structures possibly affected and coordinating our actions.
Research has been initiated at the FHWA Turner-Fairbank Highway Research Center to study the effect of chloride contaminated grout on the long-term performance of prestressing strand. This laboratory study is intended to produce the information necessary for FHWA to provide further advice to bridge owners who are affected by the chloride issue. While interim results may be available sooner, the study is currently scheduled to be completed by the end of the calendar year.
FHWA has been coordinating with the Post-Tensioning Institute (PTI) on making changes to their specifications for both on-site mixed grout and prepackaged grout that will increase assurance that appropriate quality materials are used on future projects. The new Third Edition of the PTI Specification for Grouting of Post-Tensioned Structures that incorporates these changes is expected to be available by early April of this year. In the interim, until that revised specification is issued, for all new projects that include post-tensioned applications FHWA strongly recommends that wet samples collected from grout trial batches be tested for chloride levels per ASTM C1152 Standard Test Method for Acid-Soluble Chlorides in Mortar and Concrete. This test should be performed at least once for every manufactured lot (typically one truck load or 40,000 lbs) of grout to be used. Without newer information, acceptance of the grout should continue to be based on the AASHTO and PTI recognized Cl-ion limit of 0.08% by weight of cementitious material.
In addition, to the extent practical, FHWA recommends that for on-going projects that include post-tensioned applications that grout trial batches be similarly tested for chlorides.
To promote a more consistent and better understanding of the issues and the new specifications, FHWA will be hosting a Webinar on these topics soon after the revised PTI specifications are available. Invitations to participate in the Webinar will be extended to the State DOTs through AASHTO. Immediately prior to the Webinar, through its Division Offices, FHWA intends to provide a copy of the revised PTI specifications to the State DOTs for their use and to prepare for the training.
Since November 2011, FHWA has continued to work with Sika, its engineering representative and our partners in the State DOTs to better define the extent of the issue. Table 1 presents an updated list of the bridge projects identified to date which received 300 PT grout from the Marion Plant. This is a working list and will continue to be updated as better information is developed. As stated in our previous Memorandum, the grout delivered for use on these projects may or may not contain levels of chlorides above the specified limit. Sika's engineering representative has contacted most of the owners of these projects and has begun sampling the grout used in order to establish which lots of grout are indeed affected, to what extent, and, by extension, which bridges will need additional attention.
Finally, it is recognized that many of the projects listed in Table 1 contain several structures that are individually coded for the National Bridge Inventory (NBI). In order to better manage and focus our efforts, I am asking that you work with your corresponding State DOT to assemble the following information for each potentially affected structure in those projects.
Also, if your State DOT has identified structures from other projects that are not represented by those listed in Table 1, we are interested in collecting the same information on those bridges. Once compiled, please submit this information to Reggie Holt, Concrete Bridge Specialist, FHWA Office of Bridge Technology by February 29, 2012. Reggie can be reached at Reggie.Holt@dot.gov or (202)366-4596.
Please share this information with your corresponding State DOT and inform them of the recommendations contained herein. Also, please ask your State DOT to share the information and recommendations with local owners of bridges that are included in the listed projects. We will provide additional updates as significant information becomes available. Until then, for additional
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